Dissertations / Theses on the topic 'Foreland basin'

Rivers sourced in the Himalayan mountains support more than 10% of the global population, where the majority of these people live downstream of the mountain front on the alluvial Indo-Gangetic Plain. Many of these rivers however, are also the source of devastating floods. The tendency of these rivers to flood is directly related to their large-scale morphology. In general, rivers that drain the east Indo-Gangetic Plain have channels that are perched at a higher elevation relative to their floodplain, leading to more frequent channel avulsion and flooding. In contrast, those further west have channels that are incised into the floodplain and are historically less prone to flooding. Understanding the controls on these contrasting river forms is fundamental to determining the sensitivity of these systems to projected climate change and the growing water resource demands across the Plain. This thesis examines controls on river morphology across the central portion of the Indo-Gangetic Plain drained by the Ganga River (the Ganga Plain). Specifically, the relative roles of basin subsidence, sediment grain size and sediment flux have been explored in the context of large-scale alluvial river morphology over a range of timescales. Furthermore, this thesis has developed and tested techniques that can be utilised to help quantify these variables at catchment-wide scales. This analysis has been achieved through combining new sediment grain size, pebble lithology and cosmogenic radionuclide data with quantitative topographic and sedimentological analysis of the Ganga Plain. In the first part of this thesis, I examine the contrast in channel morphology between the east and west Ganga Plain. Using topographic analysis, basin subsidence rates and sediment grain size data, I propose that higher subsidence rates in the east Ganga Plain are responsible for a deeper basin, with perched low-gradient rivers systems that are relatively insensitive to climatically driven changes in base-level. In contrast, lower basin subsidence rates in the west are associated with a shallower basin with entrenched river systems that are capable of recording climatically induced lowering of river base-level during the Holocene. Through an analysis of fan geometry, sediment grain size and lithology, I then demonstrate that gravel flux from rivers draining the central Himalaya with contributing areas spanning three orders of magnitude is approximately constant. I show that the abrasion of gravel during fluvial transport can explain this observation, where gravel sourced from more than 100 km upstream is converted into sand by the time it reaches the Plain. I attribute the over-representation of quartzitic pebble lithologies in the Plain (relative to the proportion of the upstream catchment area likely to contribute quartzite pebbles) to the selective abrasion of weaker lithologies during transport in the mountainous catchment. This process places an upper limit on the amount of coarse sediment exported into the Indo-Gangetic Plain. Finally, I consider the use of cosmogenic 10Be derived erosion rates as a method to generate sediment flux estimates over timescales of 102-104 years. Cosmogenic radionuclide samples from modern channel and independently dated Holocene terrace and flood deposits in the Ganga River reveal a degree of natural variability in 10Be concentrations close to the mountain front. This is explored using a numerical analysis of processes which are likely to drive variability in catchment-averaged 10Be concentrations. I propose that the observed variability is explained by the nature of stochastic inputs of sediment (e.g. the dominant erosional process, surface production rates, depth of landsliding, degree of mixing), and secondly, by the evacuation timescales of individual sediment deposits which buffers their impact on catchment-averaged concentrations. In landscapes dominated by high topographic relief, spatially variable climate and multiple geomorphic process domains, the use of 10Be concentrations to generate sediment flux estimates may not be truly representative. The analysis presented here suggests that comparable mean catchment-averaged 10Be concentrations can be derived through different erosional processes. For a given 10Be concentration, volumetric sediment flux estimates may therefore differ.

Mesozoic tectonic inversion in the Neuquen Basin of west-central Argentina produced two main fault systems: (1) deep faults that affected basement and syn-rift strata where preexisting faults were selectively reactivated during inversion based on their length and (2) shallow faults that affected post-rift and syn-inversion strata. Normal faults formed at high angle to the reactivated half-graben bounding fault as a result of hangingwall expansion and internal deformation as it accommodated to the shape of the curved footwall during oblique inversion. Contraction during inversion was initially accommodated by folding and internal deformation of syn-rift sedimentary wedges, followed by displacement along half-graben bounding faults. We suspect that late during inversion the weight of the overburden inhibited additional fault displacement and folding became the shortening-accommodating mechanism. A Middle Jurassic inversion event produced synchronous uplift of inversion structures across the central Neuquen Basin. Later inversion events (during Late Jurassic, Early Cretaceous, and Late Cretaceous time) produced an "inversion front" that advanced north of the Huincul Arch. Synchroneity of fault reactivation during the Callovian inversion event may be related to efficient stress transmission north of the Huincul Arch, probably due to easy reactivation of low-dip listric fault segments. This required little strain accumulation along "proximal" inversion structures before shortening was transferred to more distal structures. Later inversion events found harderto- reactivate fault segments, resulting in proximal structures undergoing significant inversion before transferring shortening. The time between the end of rifting and the different inversion events may have affected inversion. Lithosphere was probably thermally weakened at the onset of the initial Callovian inversion phase, allowing stress transmission over a large distance from the Huincul Arch and causing synchronous inversion across the basin. Later inversion affected a colder and more viscous lithosphere. Significant strain needed to accumulate along proximal inversion structures before shortening was transferred to more distal parts of the basin. Timing of inversion events along the central Neuquen Basin suggest a megaregional control by right-lateral displacement motion along the Gastre Fault Zone, an intracontinental megashear zone thought to have been active prior to and during the opening of the South Atlantic Ocean.

During Jurassic and Cretaceous time deposition in the western interior basin was controlled by a combination of subduction-related dynamic subsidence and thrust-generated flexural subsidence. Changes in the angle of oceanic plate subduction along the western margin of North America and thrust deformation in the Cordillera governed the spatial and temporal influences of these mechanisms throughout basin history. Dynamic subsidence was the primary control on basin deposition during Early-Middle Jurassic and Late Cretaceous time. During these periods, shallow-angle oceanic plate subduction beneath the western margin of North America produced convective mantle circulation and long wavelength subsidence in the western interior. A cessation of dynamic subsidence during Early Cretaceous time, brought on by an increase in the angle of subduction, is partially responsible for the ∼20 m.y. unconformity that separates the Jurassic and Cretaceous sequences in the western interior. During Late Jurassic time, thrusting in the Cordillera resulted in flexural partitioning of the back-arc region. Statal geometries in the Upper Jurassic Morrison Formation in Utah and Colorado indicate deposition in the back-bulge and forebulge depozones of the Late Jurassic foreland basin system and suggest the coeval existence of a flexurally subsiding foredeep to the west. During Early Cretaceous time, >200 km of shortening in the thrust belt resulted in uplift and erosion of the Late Jurassic foredeep and the eastward migration of foreland-basin system flexural components. Areas occupied by the Late Jurassic forebulge were incorporated into the Early Cretaceous foredeep while the Late Jurassic back-bulge depozone became the location of the Early Cretaceous forebulge. In eastern Utah and western Colorado, migration of the forebulge enhanced the regional Early Cretaceous unconformity associated with the cessation of dynamic subsidence. During late Early Cretaceous time sediment accumulation across the entire foreland-basin system may have been facilitated by the reinitiation of dynamic subsidence in the western interior. During the Late Cretaceous, thrusting in the Cordillera resulted in continued flexural subsidence of the foredeep in east-central Utah. However, increased dynamic subsidence throughout Late Cretaceous time allowed thick accumulations of strata to be deposited in the forebulge and back-bulge depozones of the foreland-basin system.

This thesis explores the controls on carbonate platform formation in foreland basins through a study of the facies, and depositional architecture, of the Middle Eocene Guara Limestone Formation, from the External Sierras, Northern Spain. The Guara Limestone Formation formed in a ramp environment on the Iberian foreland margin of the South Pyrenean Foreland Basin. The facies are foraminifera and algal limestones, with minor shallow marine siliciclastics. A facies model has been erected indicating 19 facies, grouped into 6 facies associations. Using these facies and associations, the evolution of the platform has been studied. A progradational lime-mud and clastic rich lowstand systems tract marks the initiation of deposition, the lowstand systems tract being deposited during a period of low relative sea level rise. This is overlain by an aggradational and retrogradational, carbonate grain rich, transgressive systems tract. This was deposited as the rate of relative sea level rise increased. Parasequences have been redefined herein to allow successions of a similar stratigraphic hierarchy to be encompassed in the same name. The aggradational section of the platform containing both shallowing and deepening upward parasequences. The deepening upwards parasequences were created by base level rise driven by tectonic subsidence and eustatic sea level rise. The aggradational platform margin indicates that inner-ramp production, even with the absence of coral reefs, was able to keep pace with relative sea level rise. Relative sea level rise was sufficiently rapid to preclude the development of peritidal facies and evaporites, despite suitable arid climatic conditions. Platform retrogradation, in the late transgressive systems tract, and eventual drowning, was caused by a further increase in the rate of relative sea level rise. This was created by an increase in the rate of foreland subsidence due to the formation of antiformal stacks in the Pyrenean Axial Zone to the north. Following drowning, a progradational, clastic and lime-mud rich highstand systems tract developed. Initially the rate of relative sea level rise was rapid during the highstand systems tract, this rate probably decreasing as the sequence boundary is approached. The observed increase through time of the rate of tectonic subsidence is typical of foreland basins, and is in contrast to the exponential decay of subsidence seen in passive margins. A number of other controls can be seen to have affected the Guara Limestone Formation ramp. These may affect any carbonate system; though some may be favoured specifically in foreland basin settings. Tidal action formed a series of grainstones shoals at the shelf margin, tidal effects may be favoured in narrow foreland basins due to tidal amplification, and also the limitation of wave and storm effects due to a restricted fetch. The basin was well circulated, with effective exchange between basin and platform, and salinity was normal to possibly slightly lower than normal. The biota displays a chlorozoan assemblage, but is depleted in corals due to their global decline at this time. Sediment and nutrient input onto the platform was low, leading to a resource limited environment favouring the development of large benthic foraminifera. Localised tectonics, in the form of small scale folding, produced a series of marked effects on the platform, these include: the generation of angular local unconformities, and a variation and narrowing of biofacies belts. In summary, foreland basins may display a complicated interaction between eustatic sea level variation and tectonic subsidence. In contrast to other basin types, this tectonic subsidence increases through time until eventual uplift. This provides a dominant control on the stratal architectures observed. This thesis illustrates, therefore, the potential of the use of such detailed facies and platform models to elucidate both the local, and the regional scale, controls on platform development and basin evolution.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992.
Vita.
Includes bibliographical references.
by David Speir McCormick.
Ph.D.

Introduction : la Terre au Trias inférieur et la reconquête après l’extinction fini-PermienneSitué après la limite entre le Paléozoïque et le Mésozoïque, le Trias inférieur est un intervalle court (~4Ma seulement ; Ovtcharova et al., 2006 ; Galfetti et al., 2007a ; Baresel et al., 2017). Lors de la transition entre le Permien et le Trias (PTB), la configuration tectonique de la Terre était différente, et la plupart des masses continentales étaient rassemblées en un seul super continent, la Pangée, lui-même entouré par un unique océan global, la Panthalassa (e.g., Murphy & Nance, 2008 ; Murphy et al., 2009 ; Stampfli et al., 2013).Lors de cette transition et durant le Trias inférieur, un évènement volcanique majeur, la mise en place de la grande province ignée de Sibérie (e.g., Ivanov et al., 2009, 2013), a conduit à l’émission de grande quantité de gaz à effet de serre (e.g., Galfetti et al., 2007b ; Romano et al., 2013). Ceux-ci ont contribué à l’acidification de la colonne d’eau et à l’augmentation des températures consécutivement à l’injection de CO2 dans l’atmosphère (e.g., Galfetti et al., 2007b ; Sun et al., 2012 ; Romano et al., 2013).Les perturbations environnementales qui en découlèrent ont eu des conséquences sur les milieux de dépôts associés à cette période, mais également sur les écosystèmes. Elles sont supposées avoir contribué à la mise en place de conditions délétères pour les organismes et avoir perduré durant tout le Trias inférieur, restreignant ainsi la rediversification biologique d’après-crise (e.g., Pruss & Bottjer, 2004 ; Fraiser & Bottjer, 2007 ; Bottjer et al., 2008 ; Algeo et al., 2011 ; Meyer et al., 2011 ; Bond & Wignall, 2014 ; Song et al., 2014).La limite PT fut le théâtre de la plus importante et la plus destructrice crise biologique du Phanérozoïque, et fut responsable de la disparition de plus de 90% des espèces marines (Raup, 1979), ou encore de la perte d’environ 50% des familles de tétrapodes continentaux (Benton & Newell, 2014), pour ne citer que ces deux exemples. De nombreux groupes ont été oblitérés durant cette extinction, comme par exemple les groupes caractéristiques du Paléozoïque tels que les coraux tabulés ou encore les trilobites (Sepkoski, 2002). Cependant, si la Vie a failli s’éteindre à l’aube du Mésozoïque, celle-ci a tout de même pu se reconstruire, au prix d’une rediversification communément admise comme lente et difficile dans des conditions environnementales délétères (e.g., Twitchett, 1999 ; Fraiser & Bottjer, 2007 ; Meyer et al., 2011 ; Chen & Benton, 2012). De grands paradigmes sont couramment associés à la rediversification du Trias inférieur (illustrés dans la Figure R.1a) :La présence de taxons « désastre », représentant des organismes opportunistes et généralistes qui auraient proliféré à la suite de la libération de niches écologiques laissées vacantes par les métazoaires disparus (e.g. ; Schubert & Bottjer, 1992, 1995 ; Rodland & Bottjer, 2001 ; He et al., 2007) ;Des faciès dit « anachroniques », composés de récifs exclusivement microbiens tels ceux trouvés dans les dépôts Précambriens (e.g., Schubert & Bottjer, 1992 ; Woods et al., 1999 ; Pruss & Bottjer, 2005 ; Pruss et al., 2005 ; Woods, 2009) ;Un effet « Lilliput », soit un nanisme généralisé des faunes présentes (e.g., Urbanek, 1993 ; Hautmann & Nützel, 2005 ; Payne, 2005 ; Twitchett, 2007 ; Fraiser et al., 2011 ; Metcalfe et al., 2011 ; Song et al., 2011) ;Une anoxie/euxinie généralisée dans le domaine marin, y compris littoral (e.g., Isozaki, 1997 ; Meyer et al., 2011 ; Song et al., 2012 ; Grasby et al., 2013).Fig. R.1 : a) Représentation synthétique des principaux paradigmes communément acceptés pour la rediversification biologique au cours du Trias inférieur. b) Représentation synthétique de ces mêmes paradigmes, révisés selon les données récemment recueillies dans le bassin ouest-américain (d’après Brayard, 2015). Inf. : inférieur ; m. : moyen ; s./sup. : supérieur (...)
In the wake of the Mesozoic, the Early Triassic (~251.95 Ma) corresponds to the aftermath of the most severe mass extinction of the Phanerozoic: the end-Permian crisis, when life was nearly obliterated (e.g., 90% of marine species disappeared). Consequences of this mass extinction are thought to have prevailed for several millions of years, implying a delayed recovery lasting the whole Early Triassic, if not more.Several paradigms have been established and associated to a delayed biotic recovery scenario expected to have resulted from harsh and deleterious paleoenvironments. These paradigms include a global anoxia in the marine realm, a “Lilliput” effect, and the presence of “disaster” taxa and “anachronistic” facies. However, recent works have shown a more complex global scheme for the Early Triassic recovery, and that a reevaluation of these paradigms was needed. Especially, new data from the western USA basin were critical in re-addressing these paradigms.The western USA basin is the result of a long tectono-sedimentary history that started 2 Gyr ago by the amalgamation of different lithospheric terranes forming its basement. A succession of orogenies and quiescence phases led to the formation of several successive basins in the studied area, and traces of this important geodynamical activity are still present today. The Sonoma orogeny occurred about 252 Ma in response to the eastward migration of drifting arcs toward the Laurentian craton. As a result, compressive constrains lead to the obduction of the Golconda Allochthon above the west-Pangea margin in present-day Nevada. Emplacement of this topographic load provoked the lithosphere flexuration beneath present-day Utah and Idaho to form the Sonoma Foreland Basin (SFB) studied in this work.The SFB record an excellent fossil and sedimentary record of the Early Triassic. A relatively high and complex biotic diversity has been observed there leading to describe a rapid and explosive recovery for some groups (e.g., ammonoids) in this basin after the end-Permian crisis. The sedimentary record is also well developed and has been studied extensively for a long time. Overall, these studies notably documented a marked difference between the northern and southern sedimentary succession within the basin, whose origin was poorly understood.This work therefore aims to characterize the various depositional settings in the Early Triassic SFB, as well as their paleogeographical distribution. Their controlling factors are also studied based on an original integrated method using sedimentological, paleontological, geochemical, geodynamical, structural and cartographic analyses. Aside the fossil and sedimentary discrepancy between the northern and the southern parts of the SFB, geochemical analyses provide new insights supporting this N/S dichotomy. This study also questions the validity of the geochemical signal as a tool for global correlation, as it appears to mainly reflect local forcing parameters.The geodynamical framework of the SFB was also investigated along with a numerical modelling of the rheological behavior of the basin. This work distinguishes the northern and southern parts of the basin based on markedly distinct tectonic subsidence rates during the Early Triassic: ~500 m/Myr in the northern part vs ~100m/Myr in the southern part. Origin of this remarkable difference is found in inherited properties of the basin basement itself. Indeed, different ages and therefore, rheological behaviors (i.e., rigidity to deformation and flexuration) of the basement lithospheric terranes act as a major controlling factor over the spatial distribution of the subsidence, and therefore of the sedimentary deposition. The lithosphere heritage is thus of paramount importance in the formation, development and spatio-temporal evolution of the SFB.This work leads to a new paleogeographical representation of the Sonoma Foreland Basin and its multi-parameter controlling factors (...)

This investigation focuses on the Jurassic-Eocene sedimentary record of northwestern Montana and the geometry and kinematics of the thrust belt, in order to develop a unifying geodynamic-stratigraphic model to explain the evolution of the Cordilleran retroarc of this region. Provenance and subsidence analyses suggest the onset of a foreland basin system by Middle Jurassic time. U-Pb ages of detrital zircons and detrital modes of sandstones indicate provenance from accreted terranes and deformed miogeoclinal rocks. Subsidence commenced at ∼170 Ma and followed a sigmoidal pattern characteristic of foreland basin systems. Jurassic deposits of the Ellis Group and Morrison Formation accumulated in a back-bulge depozone. A regional unconformity/paleosol zone separates the Morrison from Cretaceous deposits. This unconformity was possible result of forebulge migration, decreased dynamic subsidence, and eustatic sea level fall. The late Barremian(?)-early Albian Kootenai Formation is the first unit in the foreland that consistently thickens westward. The subsidence curve at this time begins to show a convex-upward pattern characteristic of foredeeps. The location of thrust belt structures during the Late Jurassic and Early Cretaceous is uncertain, but provenance information indicates exhumation of the Intermontane and Omineca belts, and deformation of miogeocline strata, possibly on the western part of the Purcell anticlinorium. By Albian time, the thrust belt had propagated to the east and incorporated Proterozoic rocks of the Belt Supergroup as indicated by provenance data in the Blackleaf Formation, and by cross-cutting relationships in thrust sheets involving Belt rocks. From Late Cretaceous to early Eocene time the retroarc developed a series of thrust systems including the Moyie, Snowshoe, Libby, Pinkham, Lewis-Eldorado-Steinbach-Hoadley, the Sawtooth Range and the foothills structures. The final stage in the evolution of the compressive retroarc system is recorded by the Paleocene-early Eocene Fort Union and Wasatch Formations, which are preserved in the distal foreland. A new ∼145 Km balanced cross-section indicates ∼130 km of shortening. Cross-cutting relationships, thermochronology and geochronology suggest that most shortening along the frontal part of the thrust belt occurred between the mid-Campanian to Ypresian (∼75-52 Ma), indicating a shortening rate of ∼5.6 mm/y. Extensional orogenic collapse began during the middle Eocene.

The thesis presented here spins off from the 2-year oil-industry project entitled “Salt Tectonics Modelling at Kuqa Foreland Fold and Thrust Belt, Tarim Oilfield” that was a collaboration between the American-based company China Petroleum Corporation (CNPC USA) and GEOMODELS Research Institute (via Fundació Bosch i Gimpera). This research project stems from the need to understand the structural character and evolution of the Kuqa fold- and-thrust belt (NW Xina) in order to identify exploration targets at the Mesozoic subsalt level. Specifically, the aim of the study was to identify exploration targets at the Paleogene subsalt structural level of the Kuqa foreland basin and adjoining fold and thrust belt, in particular beneath the Qiulitage fold-and-thrust system. In this scenario, the project research was focused on the definition and understanding of the different salt structures, their relationship with the geodynamic context and the different types of related hydrocarbon traps. To achieve these objectives, it was agreed to carry out six regional cross-sections, three of them balanced and restored as well as eleven balanced cross-sections of the Qiulitage fold-and-thrust system, three of them restored. In addition, regional structural maps were produced showing the salt and subsalt structures as well as their relationships with salt distribution and thickness. This line of research has been complemented with the realization of eight numerical discrete-element models and eight scaled sandbox analogue models of tectonic wedges incorporating variations in the rheology of a weak layer and in the syn- kinematic sedimentary rate. In order to accomplish these tasks, the company provided around 1500 km of 2D seismic lines and geophysical logs from numerous wells drilled in the area. In addition, two field campaigns were organized between June (15 days) and September 2015 (21 days) where structural data were collected to recognize the surface structure of the Kuqa fold-and-thrust belt. Moreover, several transects were realized during these field campaigns to recognize the surface expression of interpreted structures in the seismic lines. In this context, this thesis deals only with the results obtained from the structural analysis based on surface and subsurface data and analogue modelling. These results are presented in this manuscript which includes the following chapters. CHAPTER 1 that provides a summary of the thesis. CHAPTER 2 which provides a general introduction to the geology and the kinematic evolution of the Tian Shan intraplate range. Then, the chapter focuses in the southern frontal structure of the central Tian Shan Range, the Kuqa fold-and-thrust belt, describing both the stratigraphy and the main features of its structure. Finally, the main objectives of this thesis are presented. CHAPTER 3 that deals with the structural analysis carried out in the Kuqa fold-and- thrust belt with the field and subsurface data. The chapter shows the input data and the interpretation of both surface and subsurface data. The chapter describes the obtained results of three regional cross-sections as well as the regional structural maps of salt distribution and thickness. In addition, the chapter provides a kinematic evolution of the Kuqa fold-and-thrust belt and discusses the main parameters controlling it. CHAPTER 4 that describes the data, methodology, procedure and results obtained in the analogue modelling experiments. These experiments where designed to analyze the influence of the rheological properties of two superimposed décollement layers but mainly the one of the syn-tectonic sedimentation. So, after a brief introduction to the purpose of the experimental program and the methodology used, this chapter describes the experimental results separating them according to the applied syn-kinematic sedimentary rate. Then, the obtained results are compared and discussed mainly focusing on: the influence of the mechanical properties of a weak layer; the syn-kinematic sedimentary rate in the geometry and kinematics of brittle-viscous tectonic wedges; as well as the interaction between sub-salt and salt-detached structures. CHAPTER 5 which compares the experimental results with the structure and kinematic of the Kuqa fold-and-thrust belt defined from our structural field and subsurface analyses that is described in the Chapter 3. CHAPTER 6 which depicts the main conclusions of this thesis. CHAPTER 7 formed by the references mentioned throughout the text.
El cinturó de plecs i encavalcaments de Kuqa, situat a l’avantpaís meridional de la serralada del Tian Shan occidental, va ser deformat contractivament durant el Mesozoic superior i el Cenozoic tal com queda registrat a les seqüències sin-tectòniques continentals. A més a més, la seva evolució estructural va ser fortament controlada per la presència de sal sin- orogència (d’edat Eocè-Oligocè) i dels décollements pre-sal. En aquest context, presentem un conjunt de sis talls geològics, tres d’ells restituïts, a través del cinturó de plecs i encavalcaments de Kuqa que proporcionen una nova interpretació de la estructura per sota de les evaporites, en la qual els materials paleozoics i mesozoics estan deformats per un apilament d’encavalcaments involucrant (i) un sistema d’encavalcaments de pell fina desenganxats en nivells de carbó triàsics-juràssics, i (ii) un conjunt d’encavalcaments de basament de vergència nord. Les restitucions regionals mostren tres estadis evolutius pel cinturó de plecs i encavalcaments de Kuqa: i) una extensió mesozoica menor; ii) una compressió primerenca (Cretaci superior fins Miocè inferior) amb taxes d’escurçament i sedimentació baixes; i iii) un estadi de compressió tardana (Pliocè superior-Pleistocè) caracteritzat per un creixement major i progressiu de les taxes d’escurçament i sedimentació. Per tal d’esclarir la influència de la taxa de sedimentació, els canvis laterals en la reologia dels décollements, i la interacció entre décollements en l’estil de deformació de l’avantpaís de cinturons de plecs i encavalcaments presentem un estudi experimental que inclou quatre models analògics 3D inspirats en el cinturó de plecs i encavalcaments de Kuqa. Els resultats experimentals mostren que augmentant la taxa de sedimentació es retarda el desenvolupament d’estructures contractives frontals desenganxades a la sal, afavorint la formació i reactivació d’encavalcaments i retro-encavalcaments a les zones internes. El nostre estudi revela que a mesura que la viscositat del décollement pre-cinemàtic augmenta la deformació es propaga lentament cap a l’avantpaís. Per altre banda, les estructures sub-sal poden: (i) determinar la extensió areal de la sal i per tant l’extensió del cinturó de plecs i encavalcaments desenganxats en ell i, (ii) retardar o inclús prevenir la propagació de la deformació sobre el nivell salí cap a l’avantpaís.

The North Alpine Foreland Basin (NAFB) comprises sediments of late Eocene to middle Miocene age. The earliest deposits are the North Helvetic Flysch which are exposed in the regions of Glarus and Graubunden, eastern Switzerland. The Taveyannaz sandstones are the first thrust wedge (southerly) derived sediments of the North Helvetic Flysch. The Taveyannaz basin was divided into two sub-basins by a thrust ramp palaeohigh running ENE/WSW (parallel to the thrust front). Palaeocurrent directions were trench parallel towards the ENE. Sedimentation in the Inner basin (140m thick) is characterised by very thick bedded turbidite sands generated by thrust induced seismic events confined within the thrust-top basin. The Outer basin (240m min. thickness) comprises 10-15 sand packages (5-100m thick) formed by turbidite sands which are commonly amalgamated. Sedimentation in the Outer basin is considered to have been controlled by thrust-induced relative sea-level variations. The Inner basin underwent intense deformation at the sediment/water interface prior to the emplacement of a mud sheet over the basin whilst the sediments were partially lithified. Later tectonic deformation involved fold and thrust structures detaching in the underlying Globigerina marls. The stratigraphy of the NAFB can be considered as two shallowing upward megasequences separated by the base Burdigalian unconformity. This stratigraphy can be simulated by computer by simplifying the foreland basin/thrust wedge system into 4 parameters: 1) the effective elastic thickness of the foreland plate, 2) a transport coefficient to describe the erosion, transport and deposition of sediment, 3) the surface slope angle of the thrust wedge, 4) the thrust wedge advance rate. The Alpine thrust wedge underwent thickening during the underplating of the External Massifs at about 24-18Ma. This event is simulated numerically by slowing the thrust wedge advance rate, and increasing the slope angle and keeping all other parameters constant. This event causes rejuvenation of the forebulge, and erosion of the underlying stratigraphy, so simulating the base Burdigalian unconformity without recourse to eustasy or anelastic rheologies to the foreland plate.

The Eocene Nummulitique (Lutetian to Priabonian) has been studied in the external chains of the French Alps in Haute Savoie and Haute Provence. The Nummulitique unconformably overlies the Mesozoic passive margin succession and represents the onset of sedimentation in the Alpine Foreland Basin which formed due to lithospheric flexure caused by the advance of the Alpine orogeny. The base of the formation is marked by a regional erosional unconformity that developed during subaerial exposure of the Alpine foreland. The Nummulitique may be divided into two informal members: the lower Infranummulitique, a succession of terrigenous carbonates, and the overlying Nummulitic Limestone, a shallow marine carbonate ramp succession. The Infranummulitique is composed of terrigenous carbonates thought to have been derived from the uplifted and eroding foreland which were redeposited in local depocentres due to the topography on the erosion surface. The Infranummulitique can be divided into four facies associations: i) a lenticular conglomerate/nodular marl deposited from ephemeral streams, ii) a sheet conglomerate deposited in a marginal marine fan delta, iii) a Cerithium marl deposited in a brackish water coastal plain/lagoon and iv) a Microcodium wackestone deposited from coastal marine channels. The Nummulitic Limestone is marked by the appearance of the first fully marine foraminifera and a change from terrigenous to autochthonous carbonate sedimentation on a low-energy ramp dominated by larger benthonic foraminifera. The inner-ramp is represented by the deposition of bioclast shoals (packstones and grainstones) dominated by either calcareous red algae, Nummulites or peloids. The middle-ramp is dominated by mud-rich wackestones with a fauna of flat foraminifera, with local winnowed accumulations attributable to storm reworking. The outer ramp and basin are represented by mudstones and marls with a sparse benthos. The Nummulitique shows a marked cyclicity within an overall deepening upwards succession which is interpreted to be the combined effects of tectonic basin subsidence and high-frequency (4th order) eustatic sea-level variations. As the basin developed, the eustatic signature producing the small-scale cyclicity was successively overprinted by accelerating basin subsidence which controlled the stratigraphy of the underfilled foreland basin. Initially, the carbonate productivity is able to keep pace with the relative sea-level changes and the ramp prograded into the basin. The combination of accelerating subsidence rates and nutrient and detrital influx from the approaching orogenic wedge reduced the carbonate productivity and the ramp drowned, leading to pelagic marl deposition. The drowning surface and small-scale cyclicity have been used to correlate between measured sections within each field area, but problems occur in correlating between areas due to the migration of the foreland basin producing a diachronous sedimentary succession, which shows a similar development around the Alps, regardless of the age of the sediments. This diachroneity is evident in the two study areas with similar sediments, cycles and key surfaces developed at different stages of the basin development. The similarity in the successions demonstrates that the early sedimentation in the French Alpine Foreland Basin was controlled primarily by flexural subsidence.

The modern foreland basin straddling the eastern margin of the Andean orogen is the prime example of a retro-arc foreland basin system adjacent to a subduction orogen. While widely studied in the central and southern Andes, the spatial and temporal evolution of the Cenozoic foreland basin system in the northern Andes has received considerably less attention. This is in part due to the complex geodynamic boundary conditions, such as the oblique subduction and accretion of the Caribbean plates to the already complex interaction between the Nazca and the South American plates. In the Colombian Andes, for example, a foreland basin system has been forming since ~80 Ma over an area previously affected by rift tectonics during the Mesozoic. This setting of Cenozoic contractile deformation superposed on continental crust pre-strained by extensional processes thus represents a natural, yet poorly studied experimental set-up, where the role of tectonic inheritance on the development of foreland basin systems can be evaluated. However, a detailed documentation of the early foreland basin evolution in this part of the Andes has thus far only been accomplished in the more internal sectors of the orogen. In this study, I integrate new structural, sedimentological and biostratigraphic data with low-temperature thermochronology from the eastern sector of the Colombian Andes, in order to provide the first comprehensive account of mountain building and related foreland basin sedimentation in this part of the orogen, and to assess as to what extent pre-existent basement anisotropies have conditioned the locus of foreland deformation in space and time. In the Medina Basin, along the eastern flank of the Eastern Cordillera, I integrated detailed structural mapping and new sedimentological data with a new chronostratigraphic framework based on detailed palynology that links an eastward-thinning early Oligocene to early Miocene syntectonic wedge containing rapid facies changes with an episode of fast tectonic subsidence starting at ~30 Ma. This record represents the first evidence of topographic loading generated by slip along the principal basement-bounding thrusts in the Eastern Cordillera to the west of the basin and thus constrains the onset of mountain building in this area. A comprehensive assessment of exhumation patterns based on zircon fission-track (ZFT), apatite fission-track (AFT) analysis and thermal modelling reveals the location of these thrust loads to have been located along the contractionally reactivated Soapaga Fault in the axial sector of the Eastern Cordillera. Farther to the east, AFT and ZFT data also document the onset of thrust-induced exhumation associated with contractional reactivation of the main range-bounding Servita Fault at ~20 Ma. Associated with this episode of orogenic growth, peak burial temperature estimates based on vitrinite reflectance data in the Cenozoic sedimentary record of the adjacent Medina Basin documents earlier incorporation of the western sector of the basin into the advancing fold and thrust belt. I combined these new thermochronological data with published AFT analyses and known chronologic indicators of brittle deformation in order to evaluate the patterns of orogenic-front migration in the Andes of central Colombia. This spatiotemporal analysis of deformation reveals an episodic pattern of eastward migration of the orogenic front at an average rate of 2.5-2.7 mm/yr during the Late Cretaceous-Cenozoic. I identified three major stages of orogen propagation. First, following initiation of mountain building in the Central Cordillera during the Late Cretaceous, the orogenic front propagate eastward at slow rates (0.5-3.1 mm/yr) until early Eocene times. Such slow orogenic advance would have resulted from limited accretionary flux related to slow and oblique (SW-NE-oriented) convergence of the Farallon and South American plates during that time. A second stage of rapid orogenic advance (4.0-18.0 mm/yr) during the middle-late Eocene, and locally of at least 100 mm/yr in the middle Eocene, resulted from initial tectonic inversion of the Eastern Cordillera. I correlate this episode of rapid orogen-front migration with an increase in the accretionary flux triggered by acceleration in convergence and a rotation of the convergence vector to a more orogen-perpendicular direction. Finally, stagnation of the Miocene deformation front along former rift-bounding reactivated faults in the eastern flank of the Eastern Cordillera led to a decrease in the rates of orogenic advance. Post-late Miocene-Pliocene thrusting along the actively deforming front of the Eastern Cordillera at this latitude suggests averaged Miocene-Holocene orogen propagation rates of 1.2-2.1 mm/yr. In addition, ZFT data suggest that exhumation along the eastern flank of the orogen occurred at moderate rates of ~0.3 mm/yr during the Miocene, prior to an acceleration of exhumation since the Pliocene, as suggested by recently published AFT data. In order to evaluate the relations between thrust loading and sedimentary facies evolution in the foreland, I analyzed gravel progradation in the foreland basin system. In particular, I compared one-dimensional Eocene to Pliocene sediment accumulation rates in the Medina basin with a three-dimensional sedimentary budget based on the interpretation of ~1800 km of industry-style seismic reflection profiles and borehole data tied to the new chronostratigraphic framework. The sedimentological data from the Medina Basin reveal rapid accumulation of fluvial and lacustrine sediments at rates of up to ~ 0.5 mm/yr during the Miocene. Provenance data based on gravel petrography and paleocurrents reveal that these Miocene fluvial systems were sourced by Upper Cretaceous and Paleocene sedimentary units exposed to the west, in the Eastern Cordillera. Peak sediment-accumulation rates in the upper Carbonera Formation and the Guayabo Group occur during episodes of gravel progradation in the proximal foredeep in the Early and Late Miocene. I interpreted this positive correlation between sediment accumulation and gravel deposition as the direct consequence of thrust activity in the Servita-Lengupá Fault. This contrasts with current models relating gravel progradation to episodes of tectonic quiescence in more distal portions of foreland basin systems and calls for a re-evaluation of tectonic history interpretations inferred from sedimentary units in other mountain belts. In summary, my results document a late Eocene-early Miocene eastward advance of the topographic loads associated with the leading edge of deformation in the northern Andes of Colombia. Crustal thickening of the Eastern Cordillera associated with initiation of thrusting along the Servitá Fault illustrates that this sector of the Andean orogen acquired ~90% of its present width already by the early Miocene (~20 Ma). My data thus demonstrate that inherited crustal anisotropies, such as the former rift-bounding faults of the Eastern Cordillera, favour a non-systematic progression of foreland basin deformation through time by preferentially concentrating accommodation of slip and thrust-loading. These new chronology of exhumation and deformation associated with specific structures in the Colombian Andes also constitutes an important advance towards the understanding of models for hydrocarbon maturation, migration and trap formation along the prolific petroleum province of the Llanos Basin in the modern foredeep area.
Das Vorlandbecken, das sich an der östlichen Flanke der Anden erstreckt, ist ein prototypisches Beispiel für ein Retro-Arc-Vorlandbecken eines Subduktionszonenorogens. Im Gegensatz zu den südlichen und zentralen Anden, wurde die zeitliche und räumliche Entwicklung dieses känozoischen Systems im nördlichen Teil des Orogens weit weniger untersucht. Dies liegt unter anderem an den komplexen geodynamischen Randbedingungen, wie der schrägen Subduktion und Anlagerung der karibischen Plattengrenzen an die südamerikanische und Nazca-Platte, deren Interaktion ebenfalls komplex ist und durch unterschiedliche Konvergenzrichtungen und –geschwindigkeiten gekennzeichnet ist. Aufgrund dieser Verhältnisse hat auch die Oberplatte eine sehr differenzierte tektonische Entwicklung erfahrens. In den kolumbianischen Anden hat sich zum Beispiel seit ca. 80 Milllionen Jahren ein Vorlandbeckensystem in einem Gebiet gebildet, das während des Mesozoikums durch Rifttektonik geprägt war. Dieses Gebiet, in dem kompressive Deformation die Strukturen vorheriger extensionaler Prozesse z.T. reaktiviert und überlagert, ist daher ein natürliches, wenn auch bisher wenig erforschtes Naturlabor, um zu untersuchen, wie sich tektonische bedingte Anisotropien auf die Entwicklung von Vorlandbeckensystemen auswirken können und Änderungen in den Ablagerungsräumen und in der Faziesverteilung von Sedimenten hervorrufen. In dieser Arbeit präsentiere ich neue strukturelle, sedimentologische und biostratigraphische Daten zusammen mit neuen Informationen zur Exhumationsgeschichte mit Hilfe von Niedrigtemperatur-Thermochronologie aus dem östlichen Teil der kolumbianischen Anden, um zum ersten Mal eine vollständige Darstellung der Gebirgsbildung und zugehöriger Vorlandbeckensedimentation in diesem Teil der Anden zu liefern. Zusätzlich wird untersucht, zu welchem Ausmaß bereits existierende krustale Anisotropien den Ort der Vorlanddeformation in Raum und Zeit bestimmt haben. Im Medina Becken, an der östlichen Flanke der östlichen Kordillere, habe ich detaillierte strukturelle Kartierungen und neue sedimentologische Daten mit einem neuen chronostratigraphischen Rahmen, der auf detaillierter Palynologie basiert, verknüpft. Dieser Bezugsrahmen verbindet einen nach Osten hin ausdünnenden, syntektonischen früholigozänen bis frühmiozänen Keil, welcher rasche Faziesänderungen enthält, mit einer Phase schneller tektonischer Subsidenz, die vor ca. 30 Millionen Jahren beginnt. Dieser hier erarbeitete Datensatz stellt den ersten Beweis einer tektonisch bedingten Subsidenz dar, die durch Bewegungen entlang der Haupüberschiebungen an der Westgrenze des Vorlandes stattfanden. Dadurch wird das Einsetzen der Gebirgsbildung in diesem Gebiet zeitlich eingegrenzt. Eine umfassende Auswertung von Exhumationsmustern, die auf Zirkon- (ZFT) und Apatit-Spaltspuraltern (AFT) sowie thermischen Modellierungen beruhen, zeigt, daß diese Überschiebungsbahnen und die bedeutende Aufschiebungstätigkeit und tektonische Auflast entlang der reakivierten, vormals extensionalen Servita-Störung, im zentralen Bereich der östlichen Kordillere liegen. Weiter östlich dokumentieren AFT und ZFT Daten den Einsatz einer durch Überschiebungen hervorgerufenen Exhumation, die mit einer kompressiven Reaktivierung der großen Servita-Störung vor ca. 20 Millionen Jahren zusammenhängt. Vitrinitreflexionsdaten aus dem känozoischen Sedimentationsdatensatz des benachbarten Medina Beckens zeigen eine bedeutende Absenkung in dieser Region, bei der der westliche Sektor des Beckens schon im Anfangsstadium der orogenen Entwicklung in den nach Osten wandernden Falten- und Überschiebungsgürtel einbezogen wurde. Ich verbinde diese neuen thermochronologischen Daten mit veröffentlichten AFT Analysen und bekannten chronologischen Indikatoren für Spröddeformation, um die räumlich-zeitlichen Muster in der Entwicklung der Gebirgsfront in den Anden Zentralkolumbiens zu charakterisieren. Diese Analyse der Deformation zeigt ein episodisches Muster in der östlich gerichteten Migration der Gebirgsfront, mit einer durchschnittlichen Rate von 1.8-3.4 mm/a am Übergang von der späten Kreide zum frühen Känozoikum. Ich habe dabei drei Hauptabschnitte des lateralen Orogenwachstums identifiziert. Zuerst wandert die Gebirsfront, nach dem Beginn der Gebirgsbildung in den Zentralkordilleren während der späten Kreidezeit, ostwärts mit niedrigen Raten (0.3-3.3 mm/a) bis ins frühe Eozän. Ein solches langsames laterales Wachstum des Orogens resultiert aus Akkretionsprozessen im Zuge einer langsamen und schrägen (SW-NO orientiert) Konvergenz der Farallon- mit der südamerikanischen Platte. Eine zweite Phase schnellen Fortschreitens der Gebirgsfront mit Raten von 5.3-13.3 mm/a, lokal sogar bis zu 100 mm/a, fand während des mittleren/späten Eozäns statt und resultierte aus einer beginnenden tektonischen Inversion der östlichen Kordillere. Ich verbinde diese Phase rascher Gebirgsfrontmigration mit einem erhöhten Akkretionsfluß, der durch eine Beschleunigung der Konvergenz sowie einer Rotation des Konvergenzvektors in eine mehr rechtwinklige Richtung ausgelöst wurde. Letztlich führte eine Stagnation der Deformationsfront im Miozän entlang von ehemals riftbegrenzenden, reaktivierten Störungen an der östlichen Flanke der östlichen Kordillere zu einer Abschwächung der Raten der Gebirgsfrontmigration. Aus Überschiebungen des späten Miozän/Pliozän entlang der aktiv deformierten Front der östlichen Kordillere kann man auf durchschnittliche Bewegungsraten der Gebirgsfront von etwa 1.5-2.1 mm/a im Zeitraum Miozän bis Holozän schließen. Außerdem deuten ZFT Daten darauf hin, daß Exhumation entlang der östlichen Flanke des Orogens mit mittleren Raten von ungefähr 0.3 mm/a während des Miozäns stattfand. Im Pliozän erfolgte daraufhin eine Beschleunigung der Exhumation, wie kürzlich veröffentlichte AFT Daten nahelegen. Um die Beziehung zwischen tektonischer Auflast aufgrund der Verkürzung im Orogen und Evolution der sedimentären Fazies im Vorland zu untersuchen, habe ich die Progradation von Konglomeraten im Vorlandbeckensystem detailliert analysiert. Insbesondere habe ich eindimensionale Raten von Sedimentakkumulation vom Eozän bis zum Pliozän im Medina Becken mit einem dreidimensionalen Sedimenthaushalt verglichen. Dieser wurde aus der Interpretationen mit einer Gesamtlänge von ~2500 km seismischer Reflexionsprofile sowie Bohrlochdaten, verbunden mit dem neuen chronostratigraphischen Bezugssystem der sedimentären Ablagerungen, gewonnen. Die sedimentologischen Daten aus dem Medina Becken zeugen von rascher Akkumulation von fluviatiler und lakustriner Sedimente mit Raten von bis zu 0.5 mm/a während des Miozäns. Provenienzanalysen mittels Konglomerat-Petrographie und Paläoströmungsmessungen belegen, daß diese miozänen fluviatilen Systeme des Miozäns durch die Erosion sedimentärer Einheiten aus der oberen Kreide und dem Paläozän generiert wurden, die im Westen der östlichen Kordillere aufgeschlossen sind. Die höchsten Sedimentationsraten in der oberen Carbonera Formation und der Guayabo Gruppe finden sich während Episoden von Konglomeratprogradation der proximalen Vortiefe im frühen und späten Miozän. Ich interpretiere diese positive Korrelation zwischen Sedimentakkumulation und Konglomeratablagerung als direkte Konsequenz von Überschiebungstektonik an der Servita-Lengupá-Störung. Diese Interpretation ist allerdings im Gegensatz zu gängigen Sedimentationsmodellen Modellen, die eher eine tektonische Ruhephase mit der Progradation grober Schüttungen in den distalen Bereichen der Vorlandbecken in Verbindung bringen. Dies bedeutet, daß Interpretationen der aus Faziesverteilungen gewonnenen tektonischen Entwiklungsschritte eines Orogens auch in andeen Regionen neu bewertet werden müssen. Zusammengefaßt dokumentieren meine Ergebnisse, daß die Überschiebungsfront sowie die durch Einengung generierte Topographie und Auflast der Überschiebungsblöcke in den nördlichen kolumbianischen Anden während des späten Miozäns bis zum frühen Miozän ostwärts gewandert ist. Einengung und Krustenverdickung der östlichen Kordillere, verbunden mit beginnender Aktivität entlang der Servitá Störung, deutet an, daß dieser Bereich der Anden schon nahezu 90% seiner derzeitigen Breite bereits im Miozän (20 Ma) erreicht hattte. Die hier vorgestellten Daten zeigen also, daß ererbte krustale Anisotropien ein diachrones Voranschreiten der Vorlandbeckendeformation begünstigen. Dies geschieht durch Konzentration der Bewegungsverteilung an ererbten Störungen sowie lokalen Spannungsänderung im Vorland durch tektonische induzierte Auflasten. Diese neue Charakterisierung der Deformationsabfolge im Vorland der Anden bedeutet auch einen großen Schritt vorwärts in Richtung des Verstehens von Modellen, die das Reifen und die Wanderung von Kohlenwasserstoffen sowie die Entstehung von Ölfallen entlang der produktiven Petroleumprovinz im Llanos Becken der rezenten Vortiefe beschreiben.

Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_U-Pb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf).

Appendix A is a combination of detailed isopach maps of the Upper Cretaceous Western Interior, flexural modeling and a comparison to dynamic subsidence models as applied to the region. Using these new isopach maps and modeling, I place the previously recognized but poorly constrained shift from flexural to non-flexural subsidence at 81 Ma.

Appendix B is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation.

Appendix C is a geo-thermochronologic study to measure the lag time of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. The maximum depositional ages using DZ U-Pb match existing biostratigraphic age controls. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4–5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed from <8–9 km depth. Apatite U-Pb analyses indicate that volcanic contamination is a significant issue, without which, one cannot exclude the possibility that the youngest detrital AFT population is contaminated with significant amounts of volcanogenic apatite and does not represent source exhumation. AFT lag times are <5 Myr with relatively steady-state to slightly increasing exhumation rates. Lag time measurements indicate exhumation rates of ~0.9->>1 km/Myr.

La chaîne himalayenne est influencée par le climat global et régional et joue un rôle de barrière orographique pour les circulations atmosphériques. Son évolution tectonique et la mousson asiatique qui l’affecte en font un laboratoire idéal pour les études du lien entre la tectonique, le climat et l’érosion et leurs implications pour l’altération. Des variations latérales de taux d’exhumation ont été documentées et des études paléoclimatiques ont été réalisées dans les parties centrale et occidentale de la chaîne, mais l’initiation, l’évolution et les caractéristiques de la mousson sont encore débattues. Les intensités et les taux d’altération engendrés ont été peu étudiés, surtout dans la partie orientale de l’Himalaya.Cette thèse se focalise sur les variations latérales d’Ouest en Est de l’altération, de la végétation (évolution C3/C4) et du climat, le long de l’Himalaya depuis le Miocène à partir de l’enregistrement sédimentaire du bassin d‘avant-pays. Les données apportent des nouvelles avancées pour la compréhension de l’évolution de la mousson asiatique. Pour ce travail, j’ai étudié trois coupes pré-Siwalik et Siwalik dans l’ouest de la chaîne (les coupes Joginder Nagar, Jawalamukhi et Haripur Kolar à Himachal Pradesh, Inde), qui documentent un enregistrement sédimentaire de 20 Ma, et une coupe dans l’est (la coupe de la Kameng à Arunachal Pradesh), qui quant à elle documente 13 Ma.Les isotopes stable du carbone de la matière organique ont été utilisés pour reconstruire des changements de la végétation C3 à C4 et montrent des variations importantes entre l’ouest et l’est de la chaîne, avec une augmentation brutale des valeurs dans l’ouest à ~7 Ma, ce qui indique un changement de végétation des plantes C3 à C4. Au contraire, aucune variation n’est notée dans l’est, ce qui indique que la partie orientale caractérisée par une végétation C3 ne subit pas de changement majeur de végétation. Les variations indiquent un « asséchement » du climat et notamment une plus grande saisonnalité dans la partie occidentale de la paléoplaine. La partie orientale reste trop humide pour une évolution vers une végétation en C4, sans doute à cause de la proximité de source d’humidité du Golfe du Bengale.Le long de la coupe orientale de la Kameng, il a été nécessaire d’étudier les changements de provenance et la diagenèse, pour les éliminer, avant de reconstruire les paléo-régimes d’altération. L’analyse des minéraux lourds a permis de repérer les changements de source et de montrer que seule la partie basse de la coupe a été influencée par la diagenèse. L’évolution de la minéralogie des argiles et des éléments majeurs montre que l’altération augmente avec le temps avec une période remarquable à ~8 Ma.La compilation des trois coupes occidentales représente l’enregistrement le plus long du bassin d’avant-pays himalayen avec une durée de 20 Ma. L’évolution des argiles montre une tendance similaire entre les parties occidentale et l’orientale du bassin d’avant-pays, impliquant l’évolution vers un climat plus saisonnier à partir de ~8 Ma. Les éléments majeurs indiquent une augmentation du taux d’altération avec le temps, la partie occidentale étant généralement plus altérée que la partie orientale. Les résultats des éléments majeurs et des argiles sont cohérents avec les interprétations des isotopes stables du carbone, qui indiquent un climat plus saisonnier dans l’ouest.Enfin, une nouvelle approche permettant de reconstruire les taux d’altération à partir de la composition isotopique du lithium a été testée pour la première fois dans les sédiments miocènes du bassin d’avant-pays. Les résultats montrent à nouveau un changement dans l’ouest de la chaîne, où les valeurs isotopiques deviennent plus positives avec le temps, alors que les valeurs dans l’est restent stables. Dans l’ouest, le facteur limitant du système limitant devient l’altération, alors que dans l’est le facteur limitant est l’apport
The Himalaya orogen has major impact on global and regional climate and acts as an orographic barrier for atmospheric circulations. The interplay of the Asian monsoon system and the tectonic evolution of the mountain belt make it an ideal laboratory to study interactions between tectonics, climate and erosion, and its implications on weathering and atmospheric CO2 drawdown. Lateral variations in exhumation rates have been observed and studies on paleoclimate have been conducted in the central and western Himalaya, but the onset, the evolution and the characteristics of the monsoonal climate are still debated. Paleo weathering rates and intensities are challenging to reconstruct and remain poorly studied, especially in the eastern part of the orogen.This thesis focuses on lateral variations in climate, weathering and vegetation along the Himalayan mountain range, on weathering regimes in the eastern Himalaya since Miocene times, and on the implications for the evolution of the Asian monsoon. The foreland basin sediments of the pre-Siwalik and Siwalik Groups contain a record of tectonics and paleoclimate. The approach focuses on a direct west-east comparison; we therefore sampled three previously dated sedimentary sections in the western Himalaya, namely the Joginder Nagar, Jawalamukhi and Haripur Kolar, which combine into a timespan of 20 Ma, and the Kameng river section in the east, which spans over the last 13 Ma.Stable carbon isotopes on organic matter are used to reconstruct changes in vegetation. Stable carbon isotopes show important lateral variations, with a change toward more positive values in the west at ~7 Ma and in contrast no change in the east, indicating a change in vegetation from C3 to C4 plant in the west but not in the east. These variations implicate a change towards a dryer and more seasonal climate in the western Himalaya, whereas the climate in the eastern part remained too humid for C4 plants to evolve, due to its proximity to moisture source (Bay of Bengal).In order to reconstruct paleo weathering regimes by analyzing foreland basin sediments, it is important to take into account changes in provenance and possible influences of burial diagenesis. Results of heavy-mineral and petrographic analyses of the Kameng section provide better insight into diagenesis and provenance, showing that the older part of the Kameng section is influenced by diagenesis. Changes in provenance do not correlate with changes in clay mineralogy and major elements, which are therefore indicating an overall increase in weathering over time, with a remarkable change at ~8 Ma.The compilation of the three sections in the west represent one of the longest sedimentary records in the Himalayas, spanning over 20 Ma. Clay minerals show similar trends in the west and the east, indicating the development of a more seasonal climate starting at ~8 Ma. Major elements show a trend toward stronger weathering over time in the west and the east, but the western Himalaya are generally more weathered than in the east, which is consistent with the interpretation of the stable carbon isotope data, suggesting the climate to be more humid in the east. More runoff and erosion inhibit extensive weathering of the sediments, whereas dry sea sons with little runoff allow sediments to weather.Lithium isotopic compositions were measured on bulk sediments as a new approach to reconstruct chemical weathering rates, applied for the first time on Siwalik sediments. Results show a change in weathering intensity in the west, where lithium isotopic values become more positive over time, whereas, they stay relatively constant in the east. More positive values in the west, suggest that the system becomes more weathering-limited and more incongruent

The Nepalese Himalaya, one of the most active regions within the Himalayan Mountain belt, is characterized by a thick succession of Miocene age Siwalik sedimentary rocks deposited at its foreland basin. To date, much of its tectonic evolution, including exhumation in the Nepalese Siwalik, is poorly understood. This study of a quantitative analysis of the bedrock river parameters should provide crucial information regarding tectonic activities in the area. The study investigated geomorphic parameters of river longitudinal profiles from 54 watersheds within the Siwalik section of the Nepalese Himalaya, for the first time. A total of 140 bedrock rivers from these watersheds were selected using stream power-law function and 30-meter resolution ASTER DEM. The quantitative data from the river longitudinal profiles were integrated with published exhumation ages. Results of this study show, first, a presence of major and minor knickpoints, with a total of 305 knickpoints identified, of which 180 were major knickpoints and the rest were minor knickpoints. Further classifications of knickpoints were based on structures (lineaments extracted from SRTM DEM), lithology, and possible uplift. Second, the Normalized Steepness index (ksn) values exhibited a range from 5.3 to 140.6. Third, the concavity index of streams in the study area ranged from as low as -12.1 to as high as 31.1 and the values were consistently higher upstream of the knickpoints. Finally, integration of the river profile data with the published exhumation ages show that the regions with a high ksn value correspond to the regions with higher incision and, therefore, are likely to have high uplift. The presence of a break in ksn in the eastern section of the study area suggests that the incision is likely accelerated by Main Frontal Thrust (MFT) movements. Erosion of the thrust sheet could have influenced the rapid uplift of the Siwalik due to isostatic processes. Thus, the timing of the source-region exhumation and its rate suggests that MFT-related tectonics, and/or climate processes, likely influenced the landscape evolution of the study area. The results of this study should help in comprehending the neo-tectonic deformation of the Nepalese Himalaya.

Lower Pennsylvanian siliciclastic sedimentary rocks of the central Appalachian Basin consist predominantly of nonmarine, coal-bearing facies that developed within a fluvio-estuarine, trunk-tributary drainage system in a foreland-basin setting. Sheet-like, sandstone-mudstone bodies (up to 100 km wide and 70 m thick) developed in an axial trunk drainage system, whereas channel-like, sandstone-mudstone bodies (up to several km wide and 30 m thick) developed in tributaries oriented transverse to the thrust front. The origin of these strata has been debated largely because the paleogeomorphology and facies architecture of the New River Formation (NRF) are poorly understood. A sequence stratigraphic framework for the NRF, based on a combination of outcrop mapping and subsurface well-log analysis, reveals: 1) regionally significant erosional surfaces along the bases of sheet-like and channel-like sandstone bodies (sequence-boundaries), 2) fluvial- to estuarine-facies transitions (marine flooding surfaces), 3) erosionally based, framework-supported, quartz-pebble conglomerates (ravinement beds), and 4) regionally traceable, coarsening-upward intervals of strata (highstand deposits above maximum flooding surfaces). Using these criteria, both 3rd- and 4th-order sequences have been identified. An idealized 4th-order sequence consists of deeply incised, fluvial channel sandstone separated from overlying tidally modified estuarine sandstone and mudrock by a ravinement bed, and capped by coarsening-upward bayhead delta facies. The relative thickness of fluvial versus estuarine facies within a fourth-order sequence reflects a balance between accommodation and sediment supply within a 3rd-order relative sea level cycle. Lowermost 4th-order sequences are dominated by fluvial facies, whereas the uppermost sequences are dominated by estuarine facies. Therefore, 3rd-order sequence boundaries are interpreted to lie at the bases of the lowermost, fluvial-dominated fourth-order sequences. Coarsening-upward intervals that record the maximum landward extent of marine conditions are interpreted as highstand deposits of the composite third order sequence. Thus, the NRF consists of thick, superimposed fluvial sandstone of the lowstand systems tracts and anomalously thin transgressive and highstand systems tracts. Asymmetrical subsidence within the foreland basin resulted in westward amalgamation of multiple, 4th-order, fluvial valley-fill successions and sequence boundaries. The Early Pennsylvanian time period was characterized by global icehouse conditions and the tectonic assembly of Pangea. These events affected the geometry of the overall stratigraphic package, which can be attributed to high-magnitude, high-frequency, glacioeustatic sea-level fluctuations superimposed on asymmetric tectonic subsidence.
Master of Science

Three studies on Cordilleran foreland basin deposits in the western U.S.A. constitute this dissertation. These studies differ in scale, time and discipline. The first two studies include basin analysis, flexural modeling and detailed stratigraphic analysis of Upper Cretaceous depocenters and strata in the western U.S.A. The third study consists of detrital zircon U-Pb analysis (DZ U-Pb) and thermochronology, both zircon (U-Th)/He and apatite fission track (AFT), of Upper Jurassic to Upper Cretaceous foreland-basin conglomerates and sandstones. Five electronic supplementary files are a part of this dissertation and are available online; these include 3 raw data files (Appendix_A_raw_isopach_data.txt, Appendix_C_DZ_Data.xls, Appendix_C_UPb_apatite.xls), 1 oversized stratigraphic cross section (Appendix_B_figure_5.pdf), and 1 figure containing apatite U-Pb concordia plots (Appendix_C_Concordia.pdf). Appendix A. Subsidence in the retroarc foreland of the North American Cordillera in the western U.S.A. has been the focus of a great deal of research, and its transition from a flexural foreland basin, during the Late Jurassic and Early Cretaceous, to a dynamically subsided basin during the Late Cretaceous has been well documented. However, the exact timing of the flexural to dynamic transition is not well constrained, and the mechanism has been consistently debated. In order to address the timing, I produced new isopach maps from ~130 well log data points that cover much of Utah, Colorado, Wyoming and northern New Mexico, producing in the process, the most detailed isopach maps of the area. These isopach maps span the Turonian to mid-Campanian during the Late Cretaceous (~93–76 Ma). In conjunction with the isopach maps I flexurally modeled the Cordilleran foreland basin to identify when flexure can no longer account for the basin geometry and identified the flexural to dynamic transition to have occurred at 81 Ma. In addition, the dynamic subsidence at 81 Ma is compared to the position of the hypothesized Shatsky Oceanic Plateau and other proposed drivers of dynamic subsidence. I concluded that dynamic subsidence is likely caused by convection over the plunging nose of the Shatsky Oceanic Plateau. Appendix B. The second study is a detailed stratigraphic study of the Upper Cretaceous, (Campanian, ~76 Ma) Sego Sandstone Member of the Mesaverde Group in northwestern Colorado, an area where little research has been done on this formation. Its equivalent in the Book Cliffs area in eastern Utah has been rigorously documented and its distal progradation has been contrastingly interpreted as a result of active tectonism and shortening in the Cordilleran orogenic belt ~250 km to the west and to tectonic quiescence, flexural rebound in the thrust belt and reworking of proximal coarse grained deposits. I documented ~17 km of along depositional dip outcrops of the Sego Sandstone Member north of Rangely, Colorado. This documentation includes measured sections, paleocurrent analysis, a stratigraphic cross section, block diagrams outlining the evolution of environments of deposition through time, and paleogeographic maps correlating northwest Colorado with the Book Cliffs, Utah. The sequence stratigraphy of the Sego Sandstone Member in northwest Colorado is similar to that documented in the Book Cliffs area to the south-southwest, sharing three sequence boundaries. However, flood-tidal delta assemblages between fluvio-deltaic deposits that are present north of Rangely, Colorado are absent from the Book Cliffs area. These flood-tidal-delta assemblages are likely caused by a large scale avulsion event in the Rangely area that did not occur or was not preserved in the Book Cliffs area. In regards to tectonic models that explain distal progradation of the 76 Ma Sego Sandstone Member to be caused by tectonic quiescence and flexural rebound in the thrust belt, the first study shows that at 76 Ma, flexural processes were no longer dominant in the Cordilleran foreland, so it is inappropriate to apply models driven by flexure to the Sego Sandstone Member. Dynamic processes dominated the western U.S.A. during the Campanian, and flexural processes were subordinate. Appendix C. In order to test the tectonic vs. anti-tectonic basin-filling models for distal coarse foreland deposits mentioned above, the third study involves estimating lag times of Upper Jurassic to Upper Cretaceous conglomerates and sandstones in the Cordilleran foreland basin. Measuring lag time requires a good understanding of both the stratigraphic age of a deposit and the thermal history of sedimentary basin. To further constrain depositional age, I present twenty-two new detrital zircon U-Pb (DZ U-Pb) sample analyses, spanning Upper Jurassic to Upper Cretaceous stratigraphy in Utah, Colorado, Wyoming and South Dakota. Source exhumation ages can be measured using thermochronology. To identify a thermochronometer that measures source exhumation in the North America Cordillera, both zircon (U-Th)/He, on eleven samples, and apatite fission track (AFT) thermochronology, on eleven samples was performed. Typically, the youngest cooling age population in detrital thermochronologic analyses is considered to be a source exhumation signal; however, whether or not these apatites are exhumed apatites or derived from young magmatic and volcanic sources has been debated. To test this, I double dated the detrital AFT samples, targeting apatites with a young cooling age, using U-Pb thermochronology. Key findings are that the maximum depositional ages using DZ U-Pb match existing biostratigraphic and geochronologic age controls on basin stratigraphy. AFT is an effective thermochronometer for Lower to Upper Cretaceous foreland stratigraphy and indicates that source material was exhumed from >4–5 km depth in the Cordilleran orogenic belt between 118 and 66 Ma, and zircon (U-Th)/He suggests that it was exhumed from <8–9 km depth. Double dating apatites (with AFT and U-Pb) indicate that volcanic contamination is a significant issue; without having UPb dating of the same apatite grains, one cannot exclude the possibility that the youngest detrital AFT population is contaminated with significant amounts of volcanogenic apatite and does not represent source exhumation. AFT lag-times are 0 to 5 Myr with relatively steady-state to slightly increasing exhumation rates. We compare our data to orogenic wedge dynamics and subsidence histories; all data shows active shortening and rapid exhumation throughout the Cretaceous. Our lag-time measurements indicate exhumation rates of ~.9–>>1 km/Myr.

Sedimentary deposits have been broadly used to constrain past climate change and tectonic histories within mountain belts. This dissertation summarizes three studies that evaluate the effects of climate change and tectonics on sedimentary basin development. (1) The paleoslope estimation method, a method for calculating the threshold slope of a fluvial deposit, does not account for the stochastic variations in water depth in alluvial channels caused by climatic and autogenic processes. Therefore, we test the robustness of applying the paleoslope estimation method in a tectonic context. Based on our numerical modeling results, we conclude that if given sufficient time gravel can prograde long distances at regional slopes less than the minimum transport slope calculated with the paleoslope estimation method if water depth varies stochastically in time, and thus, caution should be exercised when evaluating regional slopes measured from the rock record in a tectonic context. (2) The role of crustal thickening, lithospheric removal, and climate change in driving surface uplift in the central Andes in southern Bolivia and changes in the creation of accommodation space and depositional facies in the adjacent foreland basin has been a topic of debate over the last decade. Our numerical modeling results show that gradual rise of the Eastern Cordillera above 2-3 km prior to 22 Ma leads to sufficient sediment accommodation for the Oligocene-Miocene foreland basin stratigraphy, and thus, the Eastern Cordillera gained the majority of its modern elevation prior to 10 Ma. Also, we conclude that major changes in grain size and depositional rates are primarily controlled by mountain-belt migration (i.e., climate change and lithospheric removal are secondary mechanisms). (3) Existing equations for predicting the long-term bedload sediment flux in alluvial channels include mean discharge as a controlling variable but do not explicitly include variations in discharge through time. We develop an analytic equation for the long-term bedload sediment flux that incorporates both the mean and coefficient of variation of discharge. Our results show that although increasing aridity leads to an increase in large discharges with respect to small discharges, long-term bedload sediment transport rates decrease for both gravel and sand-bed rivers with increasing aridity.

The sub-Middle Jurassic unconformity exhumed at Swift Reservoir, in the Rocky Mountain thrust belt of Montana, exposes structures that call for a re-evaluation of the deformation history at this locale. The unconformity separates Late Mississippian Madison Group carbonate (~340 Ma) from the transgressive basal sandstone of the Middle Jurassic (Bajocian-Bathonian) Sawtooth Formation (~170 Ma). Fieldwork established that northwest-trending, karst-widened fractures (grikes) are filled with cherty, phosphatic sandstone and conglomerate of the Sawtooth Formation and penetrate the Madison Group for 4 meters below the unconformity. Clam borings, filled with Sawtooth sandstone, pierce the unconformity surface, some of the fracture walls, and also perforate rounded clasts of Mississippian limestone that lie on the unconformity surface within basal Sawtooth conglomerate. Following deposition of the overlying foreland basin clastic-wedge, the grikes were stylolitized by layer-parallel shortening and buckled over fault-propagation anticlinal crests in the Late Cretaceous-Paleocene fold-and-thrust belt. The model proposes that the grikes record uplift and erosion followed by subsidence as the Rocky Mountain foreland experienced elastic flexure in response to tectonic loading at the plate boundary farther to the west during Early Jurassic; the forebulge opened strike-parallel fractures in the Madison Group that were karstified. The grike system contributes to the secondary porosity and permeability of the upper Madison Group; a major petroleum reservoir in the region. Grikes acted as fluid pathways during basin evolution as seen from the clay mineral assemblage and fluid inclusions contained within the grike fill. Mixed-layer illite-smectite (I/S) indicates that the grikes did not exceed 210∞ C (complete smectite-illite transition). The illite likely resulted from superstaturated fluids flushing through the foreland at the onset Laramide orogeny and may have been coincident with hydrocarbon migration. Hydrocarbon inclusions contained within the grike cements were trapped at temperatures ranging from 110∞-170∞ C; correlative with the clay temperature calculations. Recognition of the fractures as pre-middle Jurassic revises previous models, which related them to Cretaceous fracturing over the crests of fault-propagation folds, substantially changing the understanding of the hydrocarbon system.

The Andes Mountains provide an ideal natural laboratory to analyze the relationship between the tectonic evolution of a subduction margin, retroarc shortening, basin morphology, and volcanic activity. Timing of initial shortening and foreland basin development in Argentina is diachronous along strike, with ages varying by 20-30 million years. The Neuquén Basin (32°S-40°S) of southern-central Argentina sits in a retroarc position and provides a geological record of sedimentation in variable tectonic settings from the Late Triassic to the early Cenozoic including: 1.) active extension and deposition in isolated rift basins in the Late Triassic-Early Jurassic; 2.) post-rift back-arc basin from Late Jurassic-Late Cretaceous; 3.) foreland basin from Late Cretaceous to Oligocene; and 4.) variable extension and contraction along-strike from Oligocene to present. The goal of this study is to determine the timing of the transition from post-rift thermal subsidence to foreland basin deposition in the northern Neuquén Basin and then assess volcanic activity and composition during various tectonic regimes. The Aconcagua and Malargüe areas (32°S and 35°S) are located in the northern segment of the Neuquén Basin and preserve Upper Jurassic to Miocene sedimentary rocks, which record the earliest phase of shortening at this latitude. This study presents new sedimentological and detrital zircon U-Pb data from the Jurassic to latest Cretaceous sedimentary strata to determine depositional environments, stratigraphic relations, provenance, and maximum depositional ages of these units and ultimately evaluate the role of tectonics on sedimentation in this segment of the Andes. The combination of provenance, basin, and subsidence analysis shows that the initiation of foreland basin deposition occurred at ~100 Ma with the deposition of the Huitrín Formation, which recorded an episode of erosion marking the passage of the flexural forebulge. This was followed by an increase in tectonic subsidence, along with the appearance of recycled sedimentary detritus, recorded in petrographic and detrital zircons analyses, as well development of an axial drainage pattern, consistent with deposition in the flexural forebulge between 95 and 80 Ma. By ca. 70 Ma the volcanic arc migrated eastward and was a primary local source for detritus. Growth structures recorded in latest Cretaceous units very near both the Aconcagua and Malargüe study areas imply 35-40 km and 80-125 km of foreland migration between 95 and 60 Ma in the Aconcagua and Malargüe areas, respectively. Strata ranging in age from Middle Jurassic to Neogene were analyzed to determine their detrital zircon U-Pb age spectra and Hf isotopic composition to determine the relationship between magmatic output rate, tectonic regime, and crustal evolution. When all detrital zircon data are combined, significant pulses in magmatic activity occur from 190-145 Ma, and at 128 Ma, 110 Ma, 69 Ma, 16 Ma, and 7 Ma. The duration of magmatic lulls increased markedly from 10-30 million years during back-arc deposition (190-100 Ma) to ~40-50 million years during foreland basin deposition (100-~30 Ma). The long duration of magmatic lulls during foreland basin deposition could be caused by flat-slab subduction events during the Late Cretaceous and Cenozoic or by long magmatic recharge events. There are three major shifts towards positive Hf isotopic values and all are associated with regional extension events whereas compression seems to lead to more evolved isotopic values.

The Himalayan mountain chain formed between 65-40 Ma due to the closure of the Tethyan ocean and the subsequent collision of the Indian and Eurasian plates. This collision and continued plate convergence resulted in crustal thickening, southerly propagating thrust stacking, and two main periods of Barrovian metamorphism: an early 'Eo-Himalayan' metamorphism and a later Himalayan metamorphism, synchronous with a major period of thrust stacking at ca. 21 Ma. Formation of the orogen loaded the Indian plate and caused downwarping and development of a foreland basin to the south. The sedimentary rocks within the foreland basin are the Subathu Formation of Palaeocene-Mid Eocene age, the Dagshai Formation of Upper Eocene-Oligocene age, and the Kasauli Formation of lowest Miocene age. These sediments form a conformable statigraphic sequence. The Subathu Formation sediments are marine deposits, consisting of dominantly mudstones in the lower part of the succession, with limestone becoming more prominent higher up. Terrigenous material is present in minor amounts. The Dagshai Formation sediments are clastic red beds, with mudstones dominating at the base of the sequence and sandstones increasing in proportion higher up the succession. They are interpreted as being of continental origin, laid down under semi-arid conditions in a distal alluvial fan and meandering fluvial setting. The Kasuali Formation sediments are dominantly grey sandstones. Like the Dagshai Formation, they are of continental origin, but the climate had changed from semi-arid to humid by that time. The Kasauli Formation sediments are interpreted as being the product of deposition in a braided fluvial, alluvial fan environment. After deposition, the sediments were incorporated into a southward propagating imbricate thrust stack. The early foreland basin sediments are now found at three structural levels within the thrust stack; the highest structural level restores furthest to the north while the lowest structural level restores furthest to the south.

Systeme von Vorlandbecken repräsentieren bedeutende geologische Archive und dienen dem Verständnis von Rückkopplungen zwischen oberflächennahen und tektonischen Prozessen. Außerdem dokumentieren sie die Entwicklung unmittelbar angrenzender Bergketten. Die sedimentären Abfolgen in Vorlandbecken reflektieren das Gleichgewicht zwischen tektonischer Subsidenz, der Bildung langzeitlichen Akkommodationsraumes und des Sedimenteintrages, welcher wiederum die Wirksamkeit von Erosions- und Massenneuverteilungsprozessen wiederspiegelt. Um die Effekte von Klima und Tektonik in einem solchen System zu erforschen, untersuchte ich die Oligo-Miozänen Sedimente in den Vorlandbecken der südlichen Elburs Bergkette, einem intrakontinentalen Gebirge in Nord-Iran, das im Zuge der Arabisch-Eurasischen Kontinent-Kollision herausgehoben wurde. In dieser Studie der Vorlandbeckensedimente wurden Datierungstechniken angewandt (40Ar/39Ar, (U-Th)/He Thermochronologie und Magnetostratigraphie), die Sedimente und deren Herkunft analysiert und die Tonmineralogie, sowie Sauerstoff- und Kohlenstoffisotope untersucht. Die Ergebnisse zeigen, dass auf einer Zeitskala von 105 bis 106 Jahren eine systematische Korrelation zwischen „coarsening upward“ Zyklen und den sedimentären Akkumulationsraten besteht. Während sukzessiver Überschiebungsphasen werden die durch Hebung der Bergkette bereitgestellten groben Kornfraktionen in proximale Bereiche des Beckens geliefert und feinkörnige Fazies in distalen Beckenregionen abgelagert. Variationen in der Sedimentherkunft in Phasen größerer tektonischer Aktivität zeugen von erosionaler Abdeckung und/oder der Umorganisation natürlicher Entwässerungsstrukturen. Außerdem zeigen die Untersuchungen an stabilen Isotopen, dass die verstärkte tektonische Aktivität das Anwachsen der Topographie förderte und damit die Wirksamkeit einer topographischen Barriere erhöhte. Wenn aufgrund nachlassender Beckenabsenkung die grobe Kornfraktion nicht vollständig im Nahbereich des Beckens aufgenommen werden kann breitet sie sich in ferne Beckenregionen aus. Im Elburs wird die verringerte Subsidenz durch eine interne Hebung des Vorlandes hervorgerufen und ist mit einer lateralen Stapelung von Flussbetten assoziiert. Dokumentiert wird dies anhand konsequenten Schichtwachstums, tektonischer Schrägstellung und sedimentärer Umlagerung. Gleichzeitig nehmen die Sedimentationsraten zu. Die Sauerstoff-Isotope der Paläoböden zeigen, dass dieser Anstieg mit einer Phase feuchteren Klimas einhergeht, wodurch Oberflächenprozesse effizienter werden und Heraushebungssraten steigen, was eine positive Rückkopplung erzeugt. Des Weiteren zeigen die isotopischen und sedimentären Daten, dass seit 10-9 Millionen Jahren (Ma) das Klima durch saisonalen Anstieg der Niederschläge zunehmend feuchter wurde. Da bedeutende klimatische Veränderungen zu dieser Zeit auch im Mittelmeerraum und Asien beobachtet wurden, ist anzunehmen, dass die klimatische Veränderung, die im Elburs Gebirge beobachtet wird, höchstwahrscheinlich Änderungen der atmosphärischen Zirkulationen der nördlichen Hemisphäre reflektiert. Aus den Ergebnissen dieser Studie lassen sich zusätzliche Implikationen für die Entwicklung des Elburs Gebirges und die Arabisch-Eurasische kontinentale Kollisionszone ableiten. Die orogen-weite Hauptdeformation propagierte nicht gleichmäßig nach Süden, sondern seit dem Oligozän schrittweise vorwärts und rückwärts. Insbesondere von ~17,5 bis 6,2 Ma wurde das Gebirge durch eine Kombination aus frontaler Akkretion und interner Keildeformation in Schritten von 0,7 bis 2 Millionen Jahren herausgehoben. Darüber hinaus deuten die Sedimentherkunftsdaten darauf hin, dass sich noch vor 10-9 Ma die Haupteinengungsrichtung von NW-SE nach NNE-SSW veränderte. Regional erlaubt die Geschichte der untersuchten Becken und angrenzenden Gebirgszüge Rückschlüsse auf ein neues geodynamisches Model zur Entwicklung der Arabisch-Eurasischen kontinentalen Kollisionszone. Zahlreiche Sedimentbecken des Elburs Gebirges und anderer Lokalitäten der Arabisch-Eurasischen Deformationszone belegen einen Wechsel von einem tensionalen zu einem kompressionalen tektonischen Regime vor ~36 Ma . Dieser Wechsel könnte den Beginn der Subduktion von gedehnter arabischer kontinentaler Lithosphäre unter Zentral-Iran bedeuten, was zu einer moderaten Plattenkopplung und Deformation von Unter- sowie Oberplatte geführt hat. Der Anstieg der Deformationsraten im südlichen Elburs Gebirge seit ~17,5 Ma lässt vermuten, dass die Oberplatte, wahrscheinlich aufgrund steigender Plattenkopplung, seit dem frühen Miozän signifikant deformiert wurde. Diese Veränderung könnte der Subduktion mächtigerer arabischer kontinentaler Lithosphäre zugeschrieben werden und den Anfang echter kontinentaler Kollision bedeuten. Dieses Model erklärt daher die Zeitverzögerung zwischen der Initiation der Arabisch-Eurasischen kontinentalen Kollision (Eozän-Oligozän) and dem Beginn ausgedehnter Deformation in der Kollisionszone (Miozän).
Foreland-basin systems are excellent archives to decipher the feedbacks between surface and tectonic processes in orogens. The sedimentary architecture of a foreland-basin system reflects the balance between tectonic subsidence causing long-term accommodation space and sediment influx corresponding to efficiency of erosion and mass-redistribution processes. In order to explore the effects of climatic and tectonic forcing in such a system, I investigated the Oligo-Miocene foreland-basin sediments of the southern Alborz mountains, an intracontinental orogen in northern Iran, related to the Arabia-Eurasia continental collision. This work includes absolute dating methods such as 40Ar/39Ar and zircon (U-Th)/He thermochronology, magnetostratigraphy, sedimentological analysis, sandstone and conglomerate provenance study, carbon and oxygen isotope analysis, and clay mineralogy study. Results show a systematic correlation between coarsening-upward cycles and sediment accumulation rates in the basin on 105 to 106yr time scales. During thrust loading phases, the coarse-grained fraction supplied by the uplifting range is stored in the proximal part of the basin (sedimentary facies retrogradation), while fine-grained sediments are deposited in distal sectors. Variations in sediment provenance during these phases of enhanced tectonic activity give evidence for erosional unroofing phases and/or drainage-reorganization events. In addition, enhanced tectonic activity promoted the growth of topography and associated orographic barrier effects, as demonstrated by sedimentologic indicators and the analysis of stable C and O isotopes from calcareous paleosols and lacustrine/palustrine samples. Extensive progradation of coarse-grained deposits occurs during phases of decreased subsidence, when the coarse-grained fraction supplied by the uplifting range cannot be completely stored in the proximal part of the basin. In this environment, a reduction in basin subsidence is associated with laterally stacked fluvial channel deposits, and is related to intra-foreland uplift, as documented by growth strata, tectonic tilting, and sediment reworking. Increase in sediment accumulation rate associated with progradation of vertically-stacked coarse-grained fluvial channels also occurs. Paleosol O-isotope data shows that this increase is related to wetter climatic phases, suggesting that surface processes are more efficient and exhumation rates increase, giving rise to a positive feedback. Furthermore, isotopic and sedimentologic data show that starting from 10-9 Ma, climate became less arid with an increase in seasonality of precipitation. Because important changes were also recorded in the Mediterranean Sea and Asia at that time, the evidence for climatic variability observed in the Alborz mountains most likely reflects changes in Northern Hemisphere atmospheric circulation patterns. This study has additional implications for the evolution of the Alborz mountains and the Arabia-Eurasia continental collision zone. At the orogenic scale, the locus of deformation did not move steadily southward, but stepped forward and backward since Oligocene time. In particular, from ~ 17.5 to 6.2 Ma the orogen grew by a combination of frontal accretion and wedge-internal deformation on time scales of ca. 0.7 to 2 m.y. Moreover, the provenance data suggest that prior to 10-9 Ma the shortening direction changed from NW-SE to NNE-SSW, in agreement with structural data. On the scale of the entire collision zone, the evolution of the studied basins and adjacent mountain ranges suggests a new geodynamic model for the evolution of the Arabia-Eurasia continental collision zone. Numerous sedimentary basins in the Alborz mountains and in other locations of the Arabia-Eurasia collision zone record a change from a tensional (transtensional) to a compressional (transpressional) tectonic setting by ~ 36 Ma. I interpret this to reflect the onset of subduction of the stretched Arabian continental lithosphere beneath central Iran, leading to moderate plate coupling and lower- and upper-plate deformation (soft continental collision). The increase in deformation rates in the southern Alborz mountains from ~ 17.5 Ma suggests that significant upper-plate deformation must have started by the early Miocene most likely in response to an increase in degree of plate coupling. I suggest that this was related to the subduction of thicker Arabian continental lithosphere and the consequent onset of hard continental collision. This model reconciles the apparent lag time of 15-20 m.y between the late Eocene to early Oligocene age for the initial Arabia-Eurasia continental collision and the onset of widespread deformation across the collision zone to the north in early to late Miocene time.

Depositional patterns and stratal relationships in the Middle Jurassic Gypsum Spring and lower Sundance Formations were influenced by a combination of paleotopographic highs and eustatic changes in the eastern Bighorn Basin. Most of these highs are of tectonic origin related to an island arc collision to the west and assumed to be reactivations of crustal weaknesses from earlier western North American orogenies. Although overall basin geometry was affected by the encroaching tectonic load, the study area is far enough away from the orogenic front that it behaves like a passive margin in a ramp setting in response to relative sea level changes. The Middle Jurassic section in the Bighorn Basin records three major transgressive regressive cycles. Many of these contain high-order cycles identifiable by evidence of subaerial exposure in outcrop or by a geophysical log signature showing cyclic alternating peaks and troughs within a given lithologic unit. Chert pebble lag deposits have been used by previous workers to locate regional unconformities in the Bighorn Basin and throughout the Western Cordillera. One of these unconformities, the J-2 surface, is particularly enigmatic. If these lag deposits do in fact mark the J-2 unconformity the surface in the Bighorn Basin is localized and only present in the vicinity of paleotopographic highs, the Black Mountain High being the most prominent. The chert pebbles were shed off of this high and deposited locally and sporadically across two lithofacies units. The combination of paleotopography, tectonics and eustatic changes all contributed to the stratigraphy of the Middle Jurassic section. A sequence stratigraphic model was developed to gain insight into the timing of these tectonic and eustatic events in relation to deposition.
Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Geology

Following cessation of contractional deformation, the Sevier orogenic belt collapsed and spread west during a middle Eocene to middle Miocene (∼48-20 Ma) episode of crustal extension coeval with formation of metamorphic core complexes and regional magmatism. The sedimentary and structural record of this event is a network of half-grabens that extends from southern Canada to at least central Utah. Extensional structures superposed on this fold-thrust belt are rooted in the physical stratigraphy, structural relief and sole faults of preexisting thrust-fold structures. Commonly, the same detachment surfaces were used to accommodate both contractional and extensional deformation. Foreland and hinterland extensional elements of the Cordillera that are normally widely separated are uniquely collocated in central Utah where the thrust belt straddles the Archean-Proterozoic Cheyenne belt crustal suture. Here, the Charleston-Nebo allochthon, an immense leading-edge structural element of the Sevier belt collapsed during late Eocene-middle Miocene time when the sole thrust was extensionally reactivated by faults of the Deer Creek detachment fault system and the allochthon was transported at least 5-7 km back to the west. Concurrently, the north margin of the allochthon was warped by flexural-isostatic rise of a Cheyenne belt crustal welt and its footwall was intruded by crustal melts of the Wasatch igneous belt. Collectively, these elements comprise the Cottonwood metamorphic core complex. Extensional processes were also important in the formation of the Jurassic-Cretaceous Great Valley forearc basin. Advocates of a thrust-wedge hypothesis argued that this forearc experienced prolonged Jurassic-Cretaceous contraction and proposed that northwest-southeast-striking fault systems were evidence of a west-dipping blind Great Valley-Franciscan sole thrust and related backthrusts. Based on interpretation of seismic reflection, borehole, map and stratographic data, I propose that these faults and associated bedding geometries are folded synsedimentary normal faults and half-grabens. Thus, late-stage diastrophic mechanisms are not required to interpret a forearc that owes much of its present-day bedding architecture to extensional processes coeval with deposition.

Ç
iç
ekdagi basin developed on the Central Anatolian Crystalline Complex (CACC) is a foreland basin developed as the southern integral part of the Ç
ankiri Basin during the Late Paleocene to middle Oligocene. The basin has two compartments separated by the Ç
iç
ekdagi High comprises two sedimentary cycles. The oldest cycle comprises Barakli, Kocaç
ay and Bogazkö
y formationsa and is exposed both in the northern and the southern sectors. They were deposited in marine conditions. The second cycle comprises incik and Gü
vendik formations and was deposited in continental settings. The first cycle comprises uniformly south-directed paleocurrent directions in both the northern and southern sectors whereas the second cycle deposits are represented by south-directed directions in the southern sector, and bimodal directions in the northern sector. In addition, the second cycle formations contain progressive unconformities and coarsening upwards sequences indicative of thrusting. Internal structures of the units and paleostress data indicate that the basin experienced over-all compression and local extension due to flexural bending. This gave way to inversion of some of the normal faults and uplift of the Ç
iç
ekdagi High during the deposition of second cycle in the Late Eocene to middle Oligocene time which subsequently resulted in compartmentalization of the basin.

Detrital monazite Th-Pb and detrital zircon U-Pb and U-Th/He double-dating coupled with sandstone petrography and exhumation rates can be used to test for sediment recycling in Pennsylvanian sandstones within the Alleghenian clastic wedge. The Alleghenian clastic wedge is a logical system in which to test for sediment recycling as four major collisional events (Grenville, Taconic, Acadian and Alleghenian orogenies) likely reworked the continental margin and recycled siliciclastic sediment. The combination of these geochronologic and thermochronologic methods provide a more accurate assessment of the proportion of recycled sediment in the Grundy Formation (sublitharenite) and the Corbin Sandstone (quartz arenite), which past studies and the use of standard zircon U-Pb alone could not distinguish. Recognition of sediment recycling is thus critical for sedimentary provenance studies, which assume a direct path from sediment source to depositional basin. Zircon U-Pb age modes for both formations include the dominant “Grenville doublet” along with a lesser component of Granite-Rhyolite and Taconic age modes. The Corbin Sandstone is temporally more expansive, with age modes associated with the Yavapai-Mazatzal and Kenoran orogenies not present in the Grundy Formation. Monazite Th-Pb age modes are younger than zircon U-Pb for both samples, with dominant modes in the Taconic, Acadian, and Alleghenian, and only minor age modes associated with the Grenville Orogeny. The extent of sediment recycling was quantified by the difference in crystallization ages and exhumation/cooling ages of detrital zircon. This difference in time (∆t) becomes higher in the case of recycling (> ~300 Ma). A median 288 Ma ∆t cutoff value between first-cycle and multi-cycle Grenville aged zircons was calculated using post-Grenville exhumation rates. Furthermore, “detrital diagenetic monazite” grains older than the 312 Ma age of deposition are present in both the Grundy Formation and Corbin Sandstone and proves the occurrence of sediment recycling. In conclusion, most detrital grains of Grenville origin and older are likely multi-cycle, while detrital grains associated with the Taconic, Acadian, Neo-Acadian, and Alleghenian orogenies are likely first-cycle in origin.

Carbonate mud mounds from the Pennsylvanian aged San Emiliano Formation (Cantabrian Mountains, Spain) are commonly well exposed. The mounds range from 2 to 50 m in height and were observed to be primary geological features. Microfacies, ultrafacies, palaeontological and geochemical studies have revealed the composition of the mounds and surrounding carbonates. The factors and controls of mound nucleation, growth and demise have been established. The mounds are skeletal-microbial/pack-wackestones. Peloidal, homogenous and clotted micrites are the main sedimentological constituents of the mounds. Microfossils are dominant with Donezella, Claracrusta, Rothpletzella and Girvanella being common. Small foraminifera, bryozoans, corals and algae are all present within the mounds, but are more common within off-mound carbonates. The mounds show evidence of deposition within shallow water environments. The formation of the mounds was controlled by a dynamic relationship between Donezellacean algae, and microscopic encrusters. Fluctuating environmental conditions lead to the alternate dominance between the two groups, resulting in accretion and stabilisation of carbonate muds. Off-mound carbonate sediments generally show more evidence for deeper, and in some cases, higher energy environment of deposition. These carbonates are generally packstones, and two distinct types occur: a Donezella dominated carbonate with oncoids, and a cyclical micrite-marl sequence which is dominated by ‘phylloid’ algae, bryozoans and corals. Comparable mounds from the Lois-Cigüera Formation, of the local Bernesga Valley, were deposited in a deeper environment. A relationship between Donezella, Claracrusta, Rothpletzella and Girvanella was not observed within the mounds of the Lois-Cigüera Formation. These mounds are compositionally different to their San Emiliano counter-parts. The San Emiliano Fm. was deposited on the sub-aerial to submarine transition on a tilted foreland basin. Carbonate and mound deposition took place within a basin during periods of heightened tectonic activity. Carbonates of the San Emiliano Fm. were originally aragonitic. Three new fossil morphotypes are presented.

Les bassins d'avant-pays se développent au front des orogènes par flexure de la lithosphère. L'héritage structural et thermique de celle-ci joue un rôle fondamental dans leur évolution et différentes sources peuvent contribuer à la subsidence du bassin. Cette thèse analyse les effets de l'héritage d'un épisode de rift sur un rétro-bassin d'avant-pays qui s'est développé alors que la lithosphère n'avait pas retrouvé son état d'équilibre. Le Bassin Aquitain est le rétro-bassin d'avant-pays pyrénéen qui s'est développé au Campanien-Miocène. L'orogenèse pyrénéenne fait suite à un épisode de rifting Aptien-Cénomanien durant lequel la croûte a été fortement amincie et le manteau sous-continental exhumé. Les effets de l'héritage crustal dus au rift sur l'évolution du bassin sont étudiés par une analyse des structures dans la croûte, du comportement flexural de la plaque européenne et de la distribution des sédiments synorogéniques. L'évolution de la subsidence dans le bassin est étudiée par analyse de subsidence 1D d'après des données de forages. Enfin, les mécanismes d'inversion de la marge européenne sont étudiés par restauration d'une coupe structurale à échelle crustale. Cette étude aide à définir le rôle de l'héritage d'un ancien système de rift sur la mise en place et l'évolution d'un bassin d'avant-pays ainsi que le rôle des différentes sources de subsidence et leurs variations spatio-temporelles. Cette étude démontre également les liens étroits entre l'histoire du rétro-bassin d'avant-pays et les mécanismes et phases d'inversion de la marge hyper-amincie
Foreland basins develop in front of orogens by flexure of the lithosphere. When they initiate over a crust that has been affected by a previous tectonic event, structural and thermal inheritance have a fundamental role in their evolution and different sources may contribute to basin subsidence. The present work analyzes the impact of inheritance from a rifting event on a foreland basin, which develops while thermal reequilibration has not been achieved at the time of loading. The Aquitaine Basin is the Pyrenean retro-foreland basin that developed from Campanian to Miocene. The Pyrenean orogenesis follows an Aptian-Cenomanian rifting during which the continental crust is thinned and sub-continental mantle exhumed. The orogenesis starts only 10 Myr after the end of rifting. The effects of crustal inheritance due to rifting on the evolution of the basin are studied by analyzing crustal structures, flexural behavior of the European plate, and foreland succession distribution. The subsidence evolution of the basin is studied by the 1D backstripping technique using borehole data. Finally, inversion mechanisms of the European margin are studied by cross-section construction and restoration at crustal scale. This study helps to define the role of rift inheritance on the initiation and the evolution of a retro-foreland basin, as well as the relative role of subsidence sources and their variations in space and time. The present work also shows the strong relationship between the retro-foreland basin's history and both mechanism and the history and mechanisms of inversion of a hyper-extended margin

The aims of this study are to extend the established high-resolution sequence stratigraphic framework of the Madison Formation of Wyoming and southern central Montana to the correlative and genetically-related Mississippian carbonate ramp, ramp margin, and basin strata of the central Montana trough and Antler foreland basin in order to examine and discriminate the controls on depositional processes and the resulting stratigraphic architecture through space and time in tectonically-active settings. An outcrop-based, high-resolution sequence stratigraphic study of two ramp-to-basin transects, one in central Montana and the other in southwestern Montana and east-central Idaho, is conducted in order to examine these deposits across two coeval margins with differing subsidence, hydrodynamic, and physiographic configurations and histories. Independent measurements of system response to global and local forcings allows disentanglement of primary controls on deposition and allows us to gain understanding of the roles and interplay of these controls, in particular eustasy and tectonics, on the system's architectural development. Conversely, insight into the geodynamic evolution of western North America, glacioeustatic changes, and variations in global climate and oceanographic systems during the greenhouse-to-icehouse transition is gained. A series of high-resolution sequence stratigraphic cross-sections and time-slices are produced incorporating outcrop measured sections and measured sections previously collected by members of the Comparative Sedimentology Laboratory in a series of transects across the Madison ramp system. A new chronostratigraphic framework for Madison carbonates is developed by using Lower Carboniferous delta C-13 isotope excursions as isochronous tie points between ramp-top, margin, and basinal sections. These delta C-13 excursion events have been documented to be time-invariant globally due to global changes in ocean chemistry. The results of the study include resolution and discrimination of sequential foreland basin subsidence, carbonate sediment production and progradation, subsidence and uplift of foreland basin structures along a carbonate shelf edge, diachronous subsidence of discrete depocenters, and eustasy.

Thesis (Ph.D.)--University of Kentucky, 2005.
Title from document title page (viewed on August 17, 2005). Document formatted into pages; contains: xi, 214 p. : col. ill. Includes abstract and vita. Includes bibliographical references (p. 181-211).

Temporal-spatial evolution of the Central Andean foreland basin system relates directly to growth of the adjacent Andean orogenic belt during Late Cretaceous to Recent shortening. As the locus of shortening and crustal thickening propagated eastward, so too did the foreland basin system. Eastward growth of the orogenic wedge induced uplift and erosion of large portions of the basin, removing much of the detrital record of mountain building. Analyses of remnants of the Oligocene-Miocene foreland basin system in the Eastern Cordillera help define the kinematic evolution of the thrust belt in southern Bolivia. A series of north-trending depocenters, regarded collectively as a wedge-top depozone, evolved during growth of fold-thrust structures of the then-frontal part of the orogenic wedge. Growth strata and cross-cutting and onlapping relationships between contractional structures and synorogenic strata delineate the chronology of deformation. New 40Ar dates and published K-Ar dates define a minor Oligocene phase of west-vergent backthrusting followed by primarily east-vergent thrusting during Miocene time. These dates, combined with depositional histories, require synchronous and out-of-sequence thrust displacement during the Miocene. Depocenters are composed of alluvial-fan deposits on their flanks and lacustrine and braided-stream deposits in their axes. Most stratigraphic units are confined to individual depocenters, suggesting that streams rarely had sufficient power to cut across growing folds. An arid climate since ∼10-15 Ma may explain the preservation of large parts of the Late Cretaceous-Miocene foreland basin system in southern Bolivia. In contrast, northern Bolivia exhibited a humid climate over this time interval and most parts of any foreland basin were completely eroded. Critical taper theory suggests that rapid erosion in a humid fold-thrust belt may induce subcritical conditions in which thrust-front propagation is inhibited and internal deformation is promoted. An arid thrust belt may be expected to exhibit critical to supercritical conditions that favor thrust-front migration and in-sequence thrusting. Such phenomena are observed in Bolivia, suggesting that climate and erosion exert fundamental controls on the geometry and kinematics of the Andean orogenic belt.

The Alleghanian orogeny was a collision between the Gondwanan and Laurentian continents that produced the Pangean supercontinent. Mechanical and kinematic models of collisional orogens are believed to follow a critical taper geometry, where the tectonic imbrication of continental crust begins nearest to the edge of continental plate and advances toward the craton in a break- forward sequence. Studies of shear zones within the Alleghanian collisional orogen, however, suggest that most of the early deformation was translational. Propagation of craton-directed thrusts into the foreland did not occur until the latest Pennsylvanian in the southern Appalachians, and the middle-late Permian in the central Appalachians. Radiometric sedimentary provenance proxies have been applied to the late Mississippian-early Permian strata within the Appalachian foreland basin to determine the crustal composition and structural evolution of the orogen during the continental collision. U-Pb ages of detrital zircons from the early to middle Pennsylvanian sandstones suggest that most of the detritus within the Appalachian basin was recycled from Mesoproterozoic basement and Paleozoic strata of the Laurentian margin. The presence of Archean and late Paleoproterozoic age detrital zircons is cited as evidence of recycling of the Laurentian syn-rift and passive-margin sandstones. Detrital zircon ages from early-middle Permian-age sandstones of the Dunkard Group do not contain any Archean or Paleoproterozoic detrital-zircon ages, implying a source of sediment with a much more restricted age population, possibly the igneous and metamorphic internides or middle Paleozoic sandstones from the Appalachian basin. The persistance of 360-400 Ma K/Ar ages of detrital white mica suggest that the sediment was supplied from a source that was exhumed during the Devonian Acadian orogeny. Detrital-zircon and detrital-white-mica ages from Pennsylvanian-age sandstones indicate that the late Paleozoic orogen did not incorporate any significant synorogenic juvenile crust. The 87Sr/86Sr ratios of middle Pennsylvanian-early Permian lacustrine limestones within the Appalachian basin show a slight enrichment through time, suggesting that labile 87Sr-rich minerals in the Alleghanian hinterland are being exposed. Stable isotopic data from the lacustrine limestones also corroborates that the Appalachian basin became much more arid through time.

La dynamique de formation d’une chaîne de montagne peut être reconstruite à partir de l’étude des bassins réceptacles des produits d’érosion. Les travaux présentés ont été réalisés dans la partie orientale du Bassin d’Aquitaine (Corbières), à partir de l’étude de la série de Palassou. Ces sédiments, en majorité conglomératiques, traduisent une phase d’érosion majeure des reliefs, accompagnant la continentalisation des bassins au cours de l’Yprésien et la période de raccourcissement principal de l’orogenèse pyrénéenne. Trois unités tectono-stratigraphiques ont été défini dans cette série : l’unité 1 - Yprésien supérieur-Lutétien – caractérisée par la présence de galets Méso-Cénozoïques, l’unité 2 – Bartonien – caractérisée par la présence des galets de socle et l’unité 3 – Priabonien- caractérisée par la présence à nouveau de galets Méso-Cénozoïques. L’objectif de cette thèse est de comprendre le mode de remplissage du bassin d’avant-pays nord pyrénéen et son évolution au cours de l’Éocène. Ceci permettra d’appréhender la formation des reliefs à l’intérieur de la chaîne et de caractériser les différentes sources d’apport. Trois approches ont été utilisées pour reconstruire le routage des sédiments dont la première est l’étude sédimentaire et la caractérisation des environnements de dépôts des deux premières unités. Les résultats obtenus montrent l’identification de quatre séquences de remplissage sédimentaire dans l’unité 1, dont l’essentiel s’est déposé dans le synclinal de Talairan jusqu’à son débordement au cours du dépôt de la troisième séquence. Ceci amène à interpréter le synclinal de Talairan comme un bassin en piggy back. La deuxième approche est la thermochronologie basse température appliquée sur des clastes de granites issus de l’unité 2. Les résultats de traces de fission sur apatite montrent des âges plus jeunes d’est en ouest alors que les résultats de (U-Th-Sm)/He sur apatite montrent une dispersion des âges. La modélisation thermique de ces résultats indique un réchauffement post-Bartonien, traduisant une série sédimentaire plus épaisse au moment du dépôt puis partiellement érodée. La phase d’érosion est estimée comme pré-Langhienne suite aux résultats de modélisation thermique et des contraintes stratigraphiques. La troisième approche utilisée au cours de cette thèse est la datation U/Pb sur zircon. Des échantillons de matrice de conglomérat ainsi que des galets de granite issus des trois unités ont fait l’objet d’étude par cette approche. Les résultats obtenus montrent un signal Varisque majeur. Ils ont été couplés avec des analyses Raman et des directions de paléo-courant mesurés afin de caractériser les sources des sédiments pour chaque unité. Les dépôts de l’unité 1 sont issues de la Zone Nord Pyrénéenne. Les dépôts de l’unité 2 ont comme source la Zone Axiale des Pyrénées alors que les dépôts de l’unité 3 présentent un spectre d’âges assez large dont la source est la partie orientale et centrale des Pyrénées. Ces résultats ont permis de reconstruire le cheminement des sédiments dans les Corbières au cours de l’Éocène
Characterizing the evolution of the syn-orogenic sediment routing system improves our understanding of the development of mountain belts. The North Pyrenean foreland basin evolved from underfilled to overfilled during the Eocene time. The deposited syn-orogenic conglomerate, known as Palassou series, recorded the exhumation and the denudation of the mountain belt. Three tectono-sedimentary units with different facies characteristics, lateral extension and petrographic content have been identified in the Corbières region (east of the Aquitaine Basin): The first unit - late Ypresian-Lutetian - contains clasts from the Meso-Cenozoic sedimentary cover; the second unit -Bartonian – contents are of magmatic and metamorphic origin clasts and the third unit - Priabonian – contents are similar to the first unit. Clasts origins and sediment routing from source to sink are poorly constrained. This thesis is focused on the understanding of the infilling of the Corbières region during the Eocene. Multiple approaches have been combined together to reconstruct the sediment routing system during this time. The characterization of the depositional environments for the unit 1 has led to the definition of four sequences of sediment infilling that overfilled the Talairan syncline (southern Corbières) and contribute to the exportation of sediments westward. Analysis showed that the Talairan syncline was acting as a piggy-back basin during the deposition of the unit 1 sediments. Low temperature thermochronology data obtained for granite clasts from the unit 2 showed apatite fission track ages more recent from east to west and dispersed AHe ages. Inverse thermal history modelling indicates that the Corbières region experienced a post-deposition (post-Bartonian) kilometric burial and a subsequent Miocene exhumation characterized by erosion of detrital sediments. Zircon U/Pb geochronology applied for conglomerate matrix and granite clasts from the units 1, 2 and 3 allowed the identification of the source areas of the deposited sediments. Most of the obtained ages are Variscan. Results are coupled to Raman spectroscopy analysis and paleocurrent measurements in order to determine the drainage area for each unit. The unit 1 sediments are fed from the North Pyrenean Zone. The unit 2 sediments are sourced from the Axial Zone and the unit 3 sediments show multiple sources from the eastern and central Pyrenees. Obtained results allowed the reconstruction of the sediment routing system in the Corbières basin during the Eocene