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1
Gao, Dengliang. "3D seismic volume visualization and interpretation: An integrated workflow with case studies." GEOPHYSICS 74, no. 1 (January 2009): W1—W12. http://dx.doi.org/10.1190/1.3002915.
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One of the major problems in subsurface seismic exploration is the uncertainty (nonuniqueness) in geologic interpretation because of the complexity of subsurface geology and the limited dimension of the data available. Case studies from worldwide exploration projects indicate that an integrated, three-dimensional (3D) seismic volume visualization and interpretation workflow contributes to resolving the problem by mining and exposing critical geologic information from within seismic data volumes. Following 3D seismic data acquisition and processing, the interpretation workflow consists of four integrated phases from data selection and conditioning, to structure and facies characterization, to prospect evaluation and generation, to well-bore planning. In the data selection and conditioning phase, the most favored and frequently used data are the full-angle, limited-angle, and limited-azimuth stack amplitude with significant structure and facies enhancements. Signal-to-noise ratio, color scheme, dynamic range, bit resolution, and visual contrast all affect thevisibility of features of interest. In the structure and facies characterization phase, vertical slicing along arbitrary traverses demonstrates structure styles, stratigraphic architecture, and reservoir geometry in the cross-sectional view. Time/depth slicing defines lateral and vertical variability in the structural trend and areal extent in the map view. Stratal slicing and fault slicing map chronostratigraphic seismic facies and cross-stratal, along-fault seismic signature. Volume flattening and structure restoration aid in unraveling paleostructural framework and stratigraphic architecture and their growth histories. In the prospect evaluation and generation phase, a combination of volume trimming, co-rendering, transparency, attribute analysis, and attribute-body detection is instrumental in delineating volumetric extent and evaluating spatial connectivity of critical seismic features. Finally, in the well-bore planning phase, informed decision-making relies on the integration of all the information and knowledge interrogated from 3D seismic data. Most importantly, interpreters’ geologic insight and play concept are crucial to optimal well-bore planning with high geologic potential and low economic risk.
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Cross, Timothy, and Yohan Kusumanegara. "Stratigraphic Controls on Petrophysical Attributes and Fluid-Flow Pathways in an Exhumed Fluvial Reservoir." Mountain Geologist 54, no. 3 (July 2017): 129–45. http://dx.doi.org/10.31582/rmag.mg.54.3.129.
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Fluvial, floodplain and lake strata of the Green River Formation (Eocene) occur within an exhumed oil reservoir exposed in a quarry near Sunnyside, Utah. Strata in the quarry highwalls define three, asymmetrical, 15- to 20-m thick, base-level-rise genetic sequences arranged in a long-term base-level-rise (landward stepping) stacking pattern. Variable intensity of oil stain on rock surfaces is a qualitative measure of pore volumes, as all permeable facies are fully saturated with oil. Visual estimates of oil-stain intensity, combined with petrophysical measurements and petrographic analysis of the different facies, were used to define fluid-flow compartments and their boundaries. Strata and facies that functioned as fluid-flow conduits, retardants and barriers were mapped on photomosaics of the quarry highwall. Three separate fluid-flow compartments coincide with the three genetic sequences. Amalgamated fluvial sandstones at the base of each genetic sequence functioned as flow units of varying permeability and degree of interconnectedness. Laterally continuous floodplain and/or lacustrine mudstones, which cap each genetic sequence, entirely lack oil in matrix porosity and functioned as fluid-flow barriers and compartment boundaries. Petrophysical properties of specific sedimentary facies are sensitive to stratigraphic position at three spatial scales, even though the sedimentary facies appear nearly identical. At the long-term scale, porosity and permeability of the same facies (trough cross-stratified sandstone is the most common) in channel sandstones of the three genetic sequences decrease in stratigraphic succession. Within each genetic sequence, porosity and permeability are highest at the base and decrease quasilinearly to the top. Using oil-stain intensity as a proxy, porosity and permeability generally decrease from base to top of each scour-based channel macroform. Petrophysical variations coincide with subtle variations in grain size and trough cross-stratification set thickness within otherwise indistinguishable sedimentary facies. These results demonstrate that conventional crossplots of porosity/permeability versus sedimentary facies are unnecessarily broad and imprecise. When such petrophysical data are plotted in a stratigraphic context, porosity and permeability values have significantly reduced scatter. Porosity and permeability measurements and predictions of each sedimentary facies should be made from a stratigraphic perspective. From our observations of variations in intensity of oil stain, homogeneity of fluid flow may not be equated directly with facies homogeneity. At one extreme of an apparent continuum, fluid-flow pathways are tortuous and extremely variable within homogeneous, high permeability, amalgamated channel sandstones. Sweep efficiencies may be low in these cases. At an intermediate position in the continuum, increased diversity of sedimentary facies and stratigraphic variability usually cause sufficient stratigraphic separation of permeable and impermeable strata such that fluid-flow pathways are more confined and have a reduced tortuosity. Sweep efficiencies may be high in these cases. At the other extreme of the continuum, where diversity of sedimentary facies and stratigraphic variability is very high, stratigraphic units are discontinuous and restricted in area. In such cases, fluid-flow pathways are not laterally connected, and sweep efficiencies would be low.
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Vacek, František, Jindřich Hladil, and Petr Schnabl. "Stratigraphic correlation potential of magnetic susceptibility and gamma-ray spectrometric variations in calciturbiditic facies (Silurian-Devonian boundary, Prague Synclinorium, Czech Republic)." Geologica Carpathica 61, no. 4 (August 1, 2010): 257–72. http://dx.doi.org/10.2478/v10096-010-0015-2.
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Stratigraphic correlation potential of magnetic susceptibility and gamma-ray spectrometric variations in calciturbiditic facies (Silurian-Devonian boundary, Prague Synclinorium, Czech Republic)Magnetic susceptibility (MS) and gamma-ray spectrometry (GRS) stratigraphy were used for correlation and characterization of eight Silurian-Devonian (S-D) sections in the Prague Synclinorium (Czech Republic). They represent two different facies developments: lower subtidal to upper slope deposits and slope-to-basin-floor distal calciturbidites. Sections from relatively shallow- and deep-water sections are easy to compare and correlate separately, although the detailed relationship between these two facies is still not entirely clear and correlations between the two settings are difficult. This may be due to sharp facies transitions and presence of stratigraphic gaps. The MS and GRS stratigraphic variations combined with sedimentologic data have been also used for reconstruction of the evolution of the sedimentary environment. The beds close above the S-D boundary show noticeably enhanced MS magnitudes but weak natural gamma-ray emissions. It may correspond to an increased amount of terrigenous magnetic material occurring with short-term shallowing (sedimentological evidence). In deep-water sections the uppermost Silurian is characterized by high MS and GRS values. It corresponds to a supply of recycled sediment to the lower wedge which occurred during the late Pridoli regression phase. The basal Devonian beds correspond to gradual deepening, but the overlying sequences reflect other shallowing episodes which are expressed in increasing MS and gamma ray activity of rocks. The MS and GRS fluctuations are interpreted as a result of local subsidence of the sea bottom along synsedimentary growth-faults and/or a biotic event rather than of eustatic sea-level changes.
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Munsterman, D. K., R. M. C. H. Verreussel, H. F. Mijnlieff, N. Witmans, S. Kerstholt-Boegehold, and O. A. Abbink. "Revision and update of the Callovian-Ryazanian Stratigraphic Nomenclature in the northern Dutch offshore, i.e. Central Graben Subgroup and Scruff Group." Netherlands Journal of Geosciences - Geologie en Mijnbouw 91, no. 4 (December 2012): 555–90. http://dx.doi.org/10.1017/s001677460000038x.
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AbstractExploration in a mature basin requires a detailed classification and standardisation of rock stratigraphy to adequately comprehend the depositional history and prospect architecture. The pre-Quaternary Stratigraphic Nomenclature of the Netherlands compiled by Van Adrichem Boogaert & Kouwe in 1993 provided a consistent framework for use by the Dutch geological community. Over the past twenty years, new biostratigraphic techniques and continued exploration in the Netherlands have provided additional stratigraphic information. Based on this information the Late Jurassic lithostratigraphy in particular, shows significant inaccuracies. The Callovian-Ryazanian strata from the northern offshore of the Netherlands' territorial waters, termed the Central Graben Subgroup and Scruff Group, reveal a complex sedimentary history. The combination of non-marine to shallow marine lateral facies changes, repetitive log and facies characteristics in time, sea-level and climate change, salt tectonics and structural compartmentalisation hamper straightforward seismic interpretation and log correlation. Recognition of three genetic sequences by Abbink et al. in 2006 enabled an improved reconstruction of the geological history. Further improvements in refinement and reliability of the stratigraphy together with new information on the facies and ages of the successions and about the subsequent tectonostratigraphic development of the northern Dutch offshore area form the basis of the present revision. As a result, earlier lithostratigraphic models have been changed and new lithostratigraphic relationships and names are introduced in this paper.
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Isla, Manuel F., Ernesto Schwarz, Gonzalo D. Veiga, Jerónimo J. Zuazo, and Mariano N. Remirez. "Discriminating intra-parasequence stratigraphic units from two-dimensional quantitative parameters." Journal of Sedimentary Research 91, no. 8 (August 27, 2021): 887–911. http://dx.doi.org/10.2110/jsr.2020.203.
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ABSTRACT The intra-parasequence scale is still relatively unexplored territory in high-resolution sequence stratigraphy. The analysis of internal genetic units of parasequences has commonly been simplified to the definition of bedsets. Such simplification is insufficient to cover the complexity involved in the building of individual parasequences. Different types of intra-parasequence units have been previously identified and characterized in successive wave-dominated shoreface–shelf parasequences in the Lower Cretaceous Pilmatué Member of the Agrio Formation in central Neuquén Basin. Sedimentary and stratigraphic attributes such as the number of intra-parasequence units, their thickness, the proportions of facies associations in the regressive interval, the lateral extent of bounding surfaces, the degree of deepening recorded across these boundaries, and the type and lateral extent of associated transgressive deposits are quantitatively analyzed in this paper. Based on the analysis of these quantified attributes, three different scales of genetic units in parasequences are identified. 1) Bedset complexes are 10–40 m thick, basin to upper-shoreface successions, bounded by 5 to 16 km-long surfaces with a degree of deepening of one to three facies belts. These stratigraphic units represent the highest hierarchy of intra-parasequence stratigraphic units, and the vertical stacking of two or three of them typically forms an individual parasequence. 2) Bedsets are 2–20 m thick, offshore to upper-shoreface successions, bounded by up to 10 km long surfaces with a degree of deepening of zero to one facies belt. Two or three bedsets stack vertically build a bedset complex. 3) Sub-bedsets are 0.5–5 m thick, offshore transition to upper-shoreface successions, bounded by 0.5 to 2 km long surfaces with a degree of deepening of zero to one facies belt. Two or three sub-bedsets commonly stack to form bedsets. The proposed methodology indicates that the combination of thickness with the proportion of facies associations in the regressive interval of stratigraphic units can be used to discriminate between bedsets and sub-bedsets, whereas for higher ranks (bedsets and bedset complexes) the degree of deepening, lateral extent of bounding surfaces, and the characteristics of associated shell-bed deposits become more effective. Finally, the results for the Pilmatué Member are compared with other ancient and Holocene examples to improve understanding of the high-frequency evolution of wave-dominated shoreface–shelf systems.
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Di, Haibin, Cen Li, Stewart Smith, Zhun Li, and Aria Abubakar. "Imposing interpretational constraints on a seismic interpretation convolutional neural network." GEOPHYSICS 86, no. 3 (April 21, 2021): IM63—IM71. http://dx.doi.org/10.1190/geo2020-0449.1.
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With the expanding size of 3D seismic data, manual seismic interpretation becomes time-consuming and labor-intensive. For automating this process, recent progress in machine learning, in particular the convolutional neural network (CNN), has been introduced into the seismic community and successfully implemented for interpreting seismic structural and stratigraphic features. In principle, such automation aims at mimicking the intelligence of experienced seismic interpreters to annotate subsurface geology accurately and efficiently. However, most of the implementations and applications are relatively simple in their CNN architectures, which primary rely on the seismic amplitude but undesirably fail to fully use the preknown geologic knowledge and/or solid interpretational rules of an experienced interpreter who works on the same task. We have developed a generally applicable framework for integrating a seismic interpretation CNN with such commonly used knowledge and rules as constraints. Three example use cases, including relative geologic time-guided facies analysis, layer-customized fault detection, and fault-oriented stratigraphy mapping, are provided for illustrating how one or more constraints can be technically imposed and demonstrating what added values such a constrained CNN can bring. It is concluded that the imposition of interpretational constraints is capable of improving CNN-assisted seismic interpretation and better assisting the tasks of subsurface mapping and modeling.
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Rigueti, Ariely L., Patrick Führ Dal' Bó, Leonardo Borghi, and Marcelo Mendes. "Bioclastic accumulation in a lake rift basin: The Early Cretaceous coquinas of the Sergipe–Alagoas Basin, Brazil." Journal of Sedimentary Research 90, no. 2 (February 27, 2020): 228–49. http://dx.doi.org/10.2110/jsr.2020.11.
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ABSTRACT Coquinas constitute widespread deposits in lacustrine, estuarine, and shallow marine settings, where they are a valuable source of information on environmental conditions. Thick coquina successions were deposited in a series of lacustrine rift basins that formed along the Brazilian Continental Margin during the early stages of the opening of the South Atlantic Ocean, in the Early Cretaceous. In the Sergipe–Alagoas Basin, the coquina sequence, equivalent to the Morro do Chaves Formation, crops out in the Atol Quarry, and is considered a relevant analog for the economically important hydrocarbon reservoirs in the Pre-salt strata (Barremian to Aptian) of the Campos Basin (Pampo, Badejo, and Linguado oil fields), which occur only in the subsurface. The aim of this study is to generate a depositional and stratigraphic model through facies and stratigraphic analyses of a well core. These analyses allowed the geological characterization of the Morro do Chaves Formation and of its transition to the adjacent stratigraphic units, the Coqueiro Seco Formation above and the Penedo Formation below, contributing to the growing knowledge of sedimentation in rift basins and exploratory models in hydrocarbon-producing reservoirs. Facies analysis consists of sedimentological, taphonomic, and stratigraphic features of the rocks. Fourteen depositional facies were recognized, stacked into low-frequency and high-frequency, deepening-upward and shallowing-upward cycles driven by the interaction between climate and tectonism. A depositional model is presented, based on the correlation between well-core and outcrop data described in previous studies, providing insights into the spatial distribution of facies. The detailed analysis of facies and stacking patterns sheds light on depositional processes, paleoenvironmental conditions, and the evolution of the system through time, so we may better understand analogous deposits in the geological record.
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Wolpert, Philipp J., and Michael C. Poppelreiter. "Borehole-image-log characterization of deltaic deposits from a behind-outcrop well: Opportunities and limitations." Journal of Sedimentary Research 89, no. 12 (December 17, 2019): 1207–30. http://dx.doi.org/10.2110/jsr.2019.59.
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ABSTRACT Borehole imaging (BHI) is a fast and precise method for collecting subsurface data. Rock calibration may reduce uncertainties inherent in interpretations of BHI logs. However, only few data sets are published that link borehole image facies to core and outcrop facies of deltaic successions. The objective of this paper is to compare and contrast sedimentologic features as seen in BHI, core, and outcrop, using a structured and hierarchical workflow. The research will provide a global framework for the interpretation of borehole images in similar environments. A shallow, behind outcrop, research well (“Mondot-1”) drilled in NW Spain, penetrated a 185.50 m (TVD) thick section of the deltaic Sobrarbe Formation. A Formation MicroImager (FMI) borehole image log and a comprehensive well log suite was acquired in the fully cored well. The Eocene Sobrarbe Formation consists mostly of siliciclastic and some carbonate facies. Rapid vertical and lateral facies changes over a few tens of meters are observed in outcrops of the Sobrarbe Formation. The cored part of the formation is composed of argillaceous sandstone and carbonate with few diagnostic sedimentary features that can be used to constrain a conceptual depositional model. To provide a sedimentologically sound interpretation of this FMI log, we focused on layers showing diagnostic sedimentary features. Subsequently, facies associations and stratigraphic sequences were interpreted. Each facies association contained sedimentologic tie points that anchored the interpretation with diagnostic features such as slumps. This paper suggests interpreting BHI false-color images of deltaic successions using conceptual geologic constraints such as 1) depositional tie points, 2) genetically related facies associations, and 3) a hierarchical stratigraphic framework, to establish meaningful conceptual depositional models.
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Wolpert, Philipp J., and Michael C. Poppelreiter. "Borehole-image-log characterization of deltaic deposits from a behind-outcrop well: Opportunities and limitations." Journal of Sedimentary Research 89, no. 12 (December 17, 2019): 1207–30. http://dx.doi.org/10.2110/jsr.2019.75.
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ABSTRACT Borehole imaging (BHI) is a fast and precise method for collecting subsurface data. Rock calibration may reduce uncertainties inherent in interpretations of BHI logs. However, only few data sets are published that link borehole image facies to core and outcrop facies of deltaic successions. The objective of this paper is to compare and contrast sedimentologic features as seen in BHI, core, and outcrop, using a structured and hierarchical workflow. The research will provide a global framework for the interpretation of borehole images in similar environments. A shallow, behind outcrop, research well (“Mondot-1”) drilled in NW Spain, penetrated a 185.50 m (TVD) thick section of the deltaic Sobrarbe Formation. A Formation MicroImager (FMI) borehole image log and a comprehensive well log suite was acquired in the fully cored well. The Eocene Sobrarbe Formation consists mostly of siliciclastic and some carbonate facies. Rapid vertical and lateral facies changes over a few tens of meters are observed in outcrops of the Sobrarbe Formation. The cored part of the formation is composed of argillaceous sandstone and carbonate with few diagnostic sedimentary features that can be used to constrain a conceptual depositional model. To provide a sedimentologically sound interpretation of this FMI log, we focused on layers showing diagnostic sedimentary features. Subsequently, facies associations and stratigraphic sequences were interpreted. Each facies association contained sedimentologic tie points that anchored the interpretation with diagnostic features such as slumps. This paper suggests interpreting BHI false-color images of deltaic successions using conceptual geologic constraints such as 1) depositional tie points, 2) genetically related facies associations, and 3) a hierarchical stratigraphic framework, to establish meaningful conceptual depositional models.
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COOPER, MARK R., VALENTIN R. TROLL, and KIRSTIN LEMON. "The ‘Clay-with-Flints’ deposit in Northern Ireland: reassessment of the evidence for an early Paleocene ignimbrite." Geological Magazine 155, no. 8 (October 27, 2017): 1811–20. http://dx.doi.org/10.1017/s0016756817000760.
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AbstractReassessment of key geological sections, field relationships and petrographical characteristics of the Northern Ireland ‘Clay-with-Flints’ and ‘Donald's Hill Ignimbrite Formation’ show they formed dominantly by sedimentary processes. The involvement of a previously postulated pyroclastic flow during early Paleocene time is not recognized and, as such, the Donald's Hill Ignimbrite Formation stratigraphic term is discounted. Instead a multistage model of formation by sedimentary accumulation and remobilization is presented and the term Clay-with-Flints is retained. Regionally, two dominant facies are recognized in most Clay-with-Flints sections. Facies 1 was formed by an initial accumulation of flints on a chalk landscape undergoing karstification, and involved deposition of a clay matrix derived predominantly from contemporaneous erosion of subtropical soil horizons formed mainly on basalt. In Facies 2, evidence is observed for widespread remobilization of Facies 1 deposits by high-density mudflows driven by the advancement of the Antrim Lava Group, which caused the blockage of subsurface and marginalization of surface drainage. A stratigraphical constraint imposed by the presence of a supposed ignimbrite in this part of the North Atlantic Igneous Province has been problematic, but this is resolved by its identification as a diachronous, sedimentary deposit that formed until buried by either the lower or upper formations of the Antrim Lava Group.
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Moore, Shawn A., Lauren P. Birgenheier, Matthias D. Greb, Daniel Minisini, Maísa Tunik, and Julieta Omarini. "Facies heterogeneity and source potential of carbonate-mudstone-dominated distal ramp deposits, Agrio Formation, Neuquén Basin, Argentina." Journal of Sedimentary Research 90, no. 5 (May 7, 2020): 533–70. http://dx.doi.org/10.2110/jsr.2020.25.
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ABSTRACT The carbonate-mudstone-dominated Lower Cretaceous Agrio Formation is the youngest marine source rock of the hydrocarbon-prolific Neuquén Basin in Argentina, yet its facies variability and unconventional hydrocarbon potential remains relatively understudied. Detailed studies of mudstone facies variability in thick, carbonate mudstone successions deposited largely below storm wave base (i.e., chalk–marl, black shale, limestone), like the Agrio Formation, are rare and instead commonly focus on biostratigraphy or organic geochemistry alone. A continuous northern section of the Agrio Formation and a southern composite section of the lower Pilmatué and middle Avilé members, totaling ∼ 1,200 m of outcrop, were measured. From these measured sections, programmed pyrolysis (n = 339 samples), X-ray diffraction (XRD; n = 69), and thin sections (n = 69) were used to develop a high-resolution integrated macrofacies and microfacies scheme. The four most volumetrically abundant facies include detrital-quartz-silt-bearing fine mudstone (facies 1), radiolarian-bearing calcareous fine mudstone (facies 2), detrital-quartz-silt- and shell-bearing calcareous fine mudstone (facies 3), and calcareous wackestone (facies 4). All four facies are volumetrically dominated by carbonate mud matrix (i.e., micrite) that represents either 1) original pelagic coccolithophore deposition modified by diagenesis, 2) transported carbonate mud (i.e., bottom currents like contour currents or sediment gravity flows), or 3) a combination of both. Outcrop observations, XRD mineralogic trends, and petrographic variations in grain composition between detrital quartz silt, radiolarian and microfossil to macrofossil content (mainly benthic foraminifera and bivalves) distinguish the four mudstone facies. The facies scheme indicates distinctly more heterogeneous and current-influenced sedimentation in the downdip sub-storm wave base than previously described in the Agrio and in carbonate-dominated basinal settings in general. A depositional model is proposed for further testing that may prove valuable towards re-evaluating basinal carbonate mudstone successions worldwide. Utilizing TOC, S2, and HI value cutoffs, this study defines five discrete stratigraphic packages in the Agrio Formation that have the highest source potential, collectively totaling ∼ 140 m thick. The novel integration of macrofacies and microfacies analysis, stratigraphy, and a geochemical analysis allow both depositional insights and the assessment of a potential source rock. The study adds to a growing body of literature on 1) carbonate ramp (or slope) to basinal processes and 2) facies models for organic-rich, carbonate-dominated mudstone successions that are unconventional hydrocarbon systems.
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Kontorovich, A. E., A. I. Varlamov, A. S. Efimov, V. A. Kontorovich, I. V. Korovnikov, V. A. Krinin, S. V. Saraev, N. V. Sennikov, and Yu F. Filippov. "Stratigraphic Scheme of Cambrian Deposits, South of the Cis-Yenisei Area of West Siberia." Russian Geology and Geophysics 62, no. 03 (March 1, 2021): 357–76. http://dx.doi.org/10.2113/rgg20204317.
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Abstract ––In this paper we present a stratigraphic scheme for the subdivision and correlation of the Cambrian deposits in the south of the cis-Yenisei area of West Siberia, which was adopted as a current scheme by the decision of the Interdepartmental Stratigraphic Committee in 2018. This scheme is based on the data from stratigraphic test wells (Lemok-1, Averinskaya-150, Tyiskaya-1, Vostok-1, Vostok-3, Vostok-4, etс.). In the study area, two structure-facies zones were identified: Kas (Lemok-1, Averinskaya-150, Tyiskaya-1, Vostok-4, and Eloguiskaya-1 wells), where sedimentary complexes accumulated in a salt subbasin, and Ket’ (Vostok-1 and Vostok-3 wells) with the deposition in an open sea basin. The boundary between these structure-facies zones is drawn along the inferred N–S-trending barrier reef zone. The rubrication in this paper is compiled in accordance with the requirements of the Stratigraphic Code of Russia for explanatory notes for regional stratigraphic schemes. Local stratigraphic subdivisions (formations, strata) are described and compared with the adjacent Turukhansk–Irkutsk–Olekma facies region of the Siberian Platform.
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Diez, José B., Sylvie Bourquin, Jean Broutin, and Javier Ferrer. "The Iberian Permian Triassic ‘Buntsandstein’ of the Aragonian branch of the Iberian range (Spain) in the West-European sequence stratigraphical framework: a combined palynological and sedimentological approach." Bulletin de la Société Géologique de France 178, no. 3 (May 1, 2007): 179–95. http://dx.doi.org/10.2113/gssgfbull.178.3.179.
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Abstract The Permo-Triassic ‘Buntsandstein’ facies was studied from outcrops in the Aragonian branch of the Iberian range (Zaragoza, Spain). Using an integrated analysis of sedimentological and palynological data, we propose a sequence stratigraphic analysis for the Permo-Triassic deposits in this area. A comparison with the stratigraphical cycles of other parts of the Iberian domain and other peri-Tethyan basins enables us to specify the stratigraphic context of the Lower Triassic in the western European domain and characterize the importance of the Lower Triassic hiatus. The ‘Buntsandstein’ deposits studied here from the Aragonian branch occur in three outcrop areas: Tabuenca-Rodanas, Morata de Jalón and Fombuena. The Permo-Triassic deposits lie unconformably on the Hercynian (Variscan) basement. The ‘Buntsandstein’ facies were attributed to the ‘Detrital Group’ by Arribas [1984], who recognized four informal formations: the Araviana, Tierga, Calcena and Trasobares formations, in ascending stratigraphic order. Based on sedimentological criteria indicating fluvio-lacustrine environments for the Araviana cycle, the basal ‘Buntsandstein’ facies of this area can be attributed to the Permian. The discontinuity observed between the Araviana and Tierga formations, and the palaeobotanical evidence indicating an Anisian age (i.e. Middle Triassic) for the Tierga, suggests a hiatus during the Lower Triassic in this area. The Lower Triassic in Spain and many other parts of western Europe is characterized by fluvial sediments preserved in arid palaeoenvironments, associated with occasional aeolian deposits, and lacking any palaeoflora. At the scale of the western European domain, the onset of Triassic sedimentation would appear mainly in the Olenekian. Stratigraphic continuity between Permian and Triassic non-marine deposits, with sediments attributable to the Induan (lower part of the Lower Triassic), is only observed in the central Germanic Basin. In the Aragonian branch, the first Triassic sediments are dated as Anisian and characterize the retrogradational trend of a major cycle (Tierga – Calcareous Group major cycle) showing the vertical evolution from braided rivers to marine Muschelkalk deposits. At the scale of the west-European domain, the Anisian is always characterized by fluvial and fluvio-lacustrine deposits, with palaeosols, passing upward into marine deposits. Thus, the connection with the open sea was established during the Anisian. In this western Peritethyan domain, the diachronous nature of the Muschelkalk transgression is evident: the onset of Muschelkalk facies occurs during the lower Anisian in the Germanic Basin, the middle Anisian in the eastern part of the Paris Basin and the late Anisian in the Iberian Peninsula.
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Breckenridge, Jake, Angelos G. Maravelis, Octavian Catuneanu, Kevin Ruming, Erin Holmes, and William J. Collins. "Outcrop analysis and facies model of an Upper Permian tidally influenced fluvio-deltaic system: Northern Sydney Basin, SE Australia." Geological Magazine 156, no. 10 (March 7, 2019): 1715–41. http://dx.doi.org/10.1017/s0016756818000973.
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AbstractAn integrated study of sedimentological, sequence-stratigraphic and palaeodispersal analysis was applied to the Upper-Permian clastic sedimentary succession in the Northern Sydney Basin, Australia. The succession is subdivided into fifteen facies and three facies associations. The facies associations are further subdivided into eight sub-facies associations. The sedimentary evolution involves progradation from delta-front to delta-plain to fluvial depositional environments, with a significant increase in sediment grain size across the unconformable contact that separates the deltaic from the overlying fluvial system. In contrast to the delta front that is wave/storm- and/or river-influenced, the delta plain is significantly affected by tides, with the impact of tidal currents decreasing up-sequence in the delta plain. The general lack of wave-influenced sedimentary structures suggests low wave energy in the delta plain. The abrupt termination of the tidal impact in the fluvial realm relates to the steep topographic gradients and high sediment supply, which accompanied the uplift of the New England Orogen. The sequence-stratigraphic framework includes highstand (deltaic forest and topset) and lowstand (fluvial topset) systems tracts, separated by a subaerial unconformity. In contrast to most of the mud-rich modern counterparts, this is an example of a sand-rich tidally influenced deltaic system, developed adjacent to the source region. This investigation presents a depositional model for tidal successions in regions of tectonic uplift and confinement.
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Hamon, Youri, Remy Deschamps, Philippe Joseph, Daniel Garcia, and Emmanuelle Chanvry. "New insight of sedimentological and geochemical characterization of siliciclastic-carbonate deposits (Alveolina Limestone Formation, Graus-Tremp basin, Spain)." Bulletin de la Société Géologique de France 187, no. 3 (May 1, 2016): 133–53. http://dx.doi.org/10.2113/gssgfbull.187.3.133.
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Abstract This article is a first attempt of combining sedimentological analysis and geochemical systematics of the Alveolina Limestone Formation as a tool to identify the major stratigraphic surfaces, and to improve the sequence stratigraphy interpretation. This formation is Early Eocene in age and crops out in several well-exposed cliffs in the Serraduy – Roda de Isabena area (Graus-Tremp basin, NE Spain). Within this succession, nineteen carbonate and siliciclastic facies have been identified and grouped in environmental facies associations (based on their vertical stacking and lateral relationships): 1) coastal plain; 2) clastic deltaic complex; 3) shallow carbonate inner-ramp; 4) mid-ramp; 5) outer-ramp; 6) reefal facies. The depositional architectures studied in the Serraduy area can be directly assessed on the field, and a 3D reconstruction is proposed. This enables us to build a synthetic depositional model and to identify five small-scale T/R cycles, bounded by different kinds of sedimentary discontinuities : angular unconformity, firmground, erosional surface… In parallel, geochemical analyses (C and O isotopes, major, minor and trace elements) were carried out to help at hierarchizing the cycles and the boundaries previously identified. Four of them may be considered as major stratigraphic surfaces, corresponding either to regional-scale angular unconformities, or to exposure surfaces. The latter are characterized by a selective dissolution, a slight but sharp decrease in δ13CV-PDB and in Mg, Fe and Sr contents below the surface. The absence of typical sedimentary criteria of exposure (with the exception of these geochemical signatures) may be explained by short-term exposure, an arid to semi-arid climate, and a dominant low-magnesian calcite original mineralogy, precluding the development and the preservation of widespread vadose diagenetic products. A new sequence stratigraphy model for the Alveolina Limestone Fm is finally proposed and discussed.
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Ahern, Justin P., and Christopher R. Fielding. "Onset of the Late Paleozoic Glacioeustatic Signal: A Stratigraphic Record from the Paleotropical, Oil-Shale-Bearing Big Snowy Trough of Central Montana, U.S.A." Journal of Sedimentary Research 89, no. 8 (August 27, 2019): 761–83. http://dx.doi.org/10.2110/jsr.2019.44.
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Abstract In the Big Snowy Mountains of central Montana, USA, late Visean to Bashkirian strata preserve a nearly complete, but poorly documented, paleotropical stratigraphic succession that straddles the range of current estimates of the onset of the Late Paleozoic Ice Age (LPIA). Sedimentologic and stratigraphic investigation of the Otter (late Visean to Serpukhovian) and Heath (Serpukhovian) formations, with secondary focus on the overlying Tyler (late Serpukhovian to Bashkirian) and Alaska Bench (Bashkirian) formations, facilitated an appraisal of paleotropical environmental change preserved in this succession. Three facies associations reminiscent of environments currently forming in Shark Bay, Australia, were identified in the Otter Formation: shallow semi-restricted littoral platform, intertidal platform, and supratidal plain. Five facies associations broadly comparable to modern environments present in the Sunda Shelf and southern coast of the Persian Gulf were identified in the Heath Formation: offshore outer ramp, mid- to outer ramp, inner ramp, coastal plain, and sabkha. Facies associations preserved in the Heath Formation are here explained in the context of a protected, homoclinal carbonate ramp situated in a partially silled epicontinental embayment. A shift from low-magnitude relative sea-level oscillations preserved in the Otter Formation to a cyclothemic stratigraphic pattern entailing ≥ 6 fourth-order, high-frequency and high-magnitude relative sea-level fluctuations in the Heath Formation is here interpreted to record the main eustatic signal of the LPIA in central Montana. Current published biostratigraphic constraints for the observed stratigraphy estimate the main eustatic signal of the LPIA to have occurred approximately between 331 (base Serpukhovian) and 327 Ma in central Montana. A distinct upward transition from coal and paleosol-bearing depositional sequences in the lower Heath to evaporite and limestone-bearing depositional sequences in the upper Heath preserves a broad humid to arid paleoclimate shift during deposition of this unit, which influenced hydrographic circulation patterns and the resultant distribution of anoxic environments in the Big Snowy Trough during this time interval. Improved depositional and sequence stratigraphic models of the Heath Formation proposed in this study permit new insight into the theoretical distribution of, and water depth necessary to preserve, black, organic-rich claystone and shale in partially silled intracratonic basins, in addition to new temporal constraints on LPIA onset in paleotropical western Laurentia.
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López-Martínez, Rafael, Ricardo Barragán, Daniela Reháková, and Jorge Luis Cobiella-Reguera. "Calpionellid distribution and microfacies across the Jurassic/ Cretaceous boundary in western Cuba (Sierra de los Órganos)." Geologica Carpathica 64, no. 3 (June 1, 2013): 195–208. http://dx.doi.org/10.2478/geoca-2013-0014.
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Abstract A detailed bed-by-bed sampled stratigraphic section of the Guasasa Formation in the Rancho San Vicente area of the “Sierra de los Órganos”, western Cuba, provides well-supported evidence about facies and calpionellid distribution across the Jurassic/Cretaceous boundary. These new data allowed the definition of an updated and sound calpionellid biozonation scheme for the section. In this scheme, the drowning event of a carbonate platform displayed by the facies of the San Vicente Member, the lowermost unit of the section, is dated as Late Tithonian, Boneti Subzone. The Jurassic/Cretaceous boundary was recognized within the facies of the overlying El Americano Member on the basis of the acme of Calpionella alpina Lorenz. The boundary is placed nearly six meters above the contact between the San Vicente and the El Americano Members, in a facies linked to a sea-level drop. The recorded calpionellid bioevents should allow correlations of the Cuban biozonation scheme herein proposed, with other previously published schemes from distant areas of the Tethyan Domain.
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Hou, Pengfei, Lesli J. Wood, and Zane R. Jobe. "Tectonic–sedimentary interplay of a confined deepwater system in a foreland basin setting: the Pennsylvanian lower Atoka Formation, Ouachita Mountains, U.S.A." Journal of Sedimentary Research 91, no. 7 (July 15, 2021): 683–709. http://dx.doi.org/10.2110/jsr.2020.064.
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ABSTRACT Submarine fans deposited in structurally complex settings record important information on basin evolution and tectonic–sedimentary relationships but are often poorly preserved in outcrops due to syndepositional and post depositional deformation. This study aims to understand the influence of tectonics on the deposition of the synorogenic Pennsylvanian lower Atoka submarine fan system deposited in a structurally complex foreland basin during the Ouachita orogeny. This study is a synthesis of new outcrop stratigraphic data as well as published stratigraphic and structural data. The lower Atoka crops out in the Ouachita Mountains and the southern Arkoma Basin and is divided into three structural–depositional zones: the foredeep, the wedge top, and the continental foreland. The mean paleoflow is axial, and each zone exhibits unique patterns in facies distribution. The foredeep consists of two fan systems, a large westward-prograding fan that exhibits significant longitudinal and lateral facies changes, and a small eastward-prograding fan on the western part. The wedge top consists of a westward-prograding fan that exhibits subtle longitudinal facies change. The continental foreland consists of small slope fan systems along the northern and western margins. By comparing to basin morphology and structural styles, we interpret the facies distribution patterns in the three zones as the result of different combinations of lateral structural confinement, axial and lateral sediment supply, and paleogeography. This study provides an improved and comprehensive understanding of the lower Atoka deepwater system and has implications for deciphering the tectonic–sedimentary relationships in laterally confined submarine fan systems.
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Lin, Wen, David Kynaston, Curtis Ferron, Janok P. Bhattacharya, and William Matthews. "Depositional and sequence stratigraphic model of transgressive shelf sandstone: The Late Cretaceous Tocito Sandstone, San Juan Bain, New Mexico, U.S.A." Journal of Sedimentary Research 91, no. 4 (April 1, 2021): 415–32. http://dx.doi.org/10.2110/jsr.2020.121.
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ABSTRACT There has long been debate about the origin of long, linear, isolated shallow marine sandstones. In the 1980s these were routinely interpreted as wave- or tide-modulated shelf sandstones. With the advent of sequence stratigraphy, many of these sandstones were reinterpreted as top-truncated forced-regressive to lowstand delta or shoreface, inviting the question regarding whether the concept of a shelf sandstones remain a viable depositional model. More recent syntheses demonstrate that shelf sands tend to be derived by reworking of underlying sediment through transgressive erosion and show varying levels of detachment and reworking into discrete ridges and bars by wave and tidal processes as they become more evolved. The Late Cretaceous Tocito Sandstone in the Western Interior Seaway, which overlies the regressive Gallup Formation, is a candidate for a transgressive shelf sandstone. In this study, we present detailed facies analysis, based on sedimentological sections measured from well-exposed outcrops of the Tocito Sandstone and its related stratigraphic units in northwest New Mexico, USA. With high-resolution sequence stratigraphic control, facies analysis, detrital-zircon anatomy, and petrographic analysis are integrated to investigate the sequence stratigraphic evolution and depositional processes of the Tocito Sandstone. Detrital zircons indicate that the Tocito, Torrivio, and Gallup deposits are derived from different source areas, and therefore imply separate sequence stratigraphic origins. The Tocito Sandstone is interpreted to have been deposited as shelf sand ridges in retrogradational estuarine to drowned-barrier-system environments with tidal and wave influence, characterized by intense bioturbation. The Tocito was deposited in an overall transgressive systems tract and sourced from reworking of the underlying Torrivio and Gallup units through processes of transgressive erosion.
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Chatterjee, Priyabrata, Utpalendu Kuila, B. N. S. Naidu, Hriday Jyoti Bora, Anil Malkani, Sandipan Dutta, Arpita Mandal, Premanand Mishra, and Pinakadhar Mohapatra. "Fatehgarh lacustrine turbidite potential, Barmer Basin, India." Leading Edge 38, no. 4 (April 2019): 280–85. http://dx.doi.org/10.1190/tle38040280.1.
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Global discovered resources of oil and gas in giant stratigraphic and structural-stratigraphic combination traps have increased by nearly 50% in the last 17 years. Among the biggest contributors are the large discoveries in deepwater turbidite systems in passive margins and rift basins. The current study area is located in the Barmer Basin in northwestern India. Barmer Basin is a prolific petroliferous basin with major oil discoveries in structural plays including Mangala, Bhagyam, and Aishwariya fields. The principal reservoirs in the structural highs are high-quality fluvial sandstones of the Paleocene Fatehgarh Formation. Lacustrine turbidite plays have been discovered in the overlying Paleocene Barmer Hill Formation, albeit with moderate to poor reservoir quality. The potential exists, however, for finding off-structure lacustrine deepwater turbidite plays in the Paleocene Fatehgarh with reservoir quality comparable to the high-quality fluvial facies encountered updip in the structural plays. An integrated approach was adopted to identify stratigraphic entrapments across the basin to chase high-quality Fatehgarh reservoirs. Gross depositional environment maps integrating new geoscientific data were created, followed by well-calibrated seismic geomorphology and seismic facies interpretations to identify the distal lacustrine deepwater turbidite system fed by the updip fluvial Fatehgarh systems. Worldwide, the critical risk elements associated with such plays are reservoir presence, quality, and lateral seal. Geophysical tools like unsupervised seismic waveform classification, spectral decomposition, and seismic inversion were applied to the available seismic data, and the results were integrated with the regional geology and well facies information to derisk the critical risk segments.
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Opuwari, M., M. Amponsah-Dacosta, S. Mohammed, and N. Egesi. "Delineation of sandstone reservoirs of Pletmos Basin offshore South Africa into Flow Units using Core Data." South African Journal of Geology 123, no. 4 (October 26, 2020): 479–92. http://dx.doi.org/10.25131/sajg.123.0032.
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Abstract The present study is focused on the comparison of petrophysical rock typing and zonation methods of the Valanginian age sandstone in the Pletmos Basin offshore South Africa, to produce a zonation scheme for the low-permeability shaly sandstone reservoirs from core porosity and permeability data. The Valanginian age sediments of the Lower Cretaceous consist predominantly of a shallow marine sequence with interbeds of siltstone, claystone, generally fine-grained sandstone, and glauconitic, with varying amounts of an argillaceous matrix. A core description report was used in conjunction with a gamma-ray log to group rock types into different facies based on texture and grain size. Three different facies were identified as facies 1, a moderately sorted fine to medium-grained glauconitic sandstone; facies 2, a fine to very fine-grained glauconitic sandstone, moderately sorted; facies 3, a very fine sandstone to siltstone, laminated, argillaceous and bioturbated. Three independent reservoir zonation methods (Winland r35 pore throat, Hydraulic Flow Unit, and Stratigraphic Modified Lorenz Plot) were applied to three wells (SW1, SW2, and SW3) for which wireline logs, core porosity, and permeability data are available. Results were analyzed and compared with facies used as a context for the identification of rock types and zones. The results revealed eleven zones, grouped as moderate, very-low, and tight zones. The moderate flow zone is the best reservoir quality rock composed of macroporous rock type, ranked, as good rock type associated with facies 1. Three very-low flow zones were identified, which are of a microporous rock type, ranked as poor quality rock, associated with facies 2. Eight tight zones were revealed, which are of nanoporous rock type ranked as an impervious rock. The tight flow zone is the most reduced rock quality associated with facies 3. This study has developed a zonation scheme that will be used to locate other flow zones as well as to investigate whether the units/zones identified extend to other parts of the field.
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Alsop, G. I. "The geometry and structural evolution of a crustal-scale Caledonian fold complex: the Ballybofey Nappe, northwest Ireland." Geological Magazine 131, no. 4 (July 1994): 519–37. http://dx.doi.org/10.1017/s0016756800012139.
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AbstractThe gross geometries exhibited by crustal-scale fold nappes are considered a consequence of both original stratigraphic relationships associated with sub-basin configuration, coupled with the nature of the structural regime and tectonic processes involved in the generation of the nappe pile. The Neo-Proterozoic Dalradian metasediments of northwestern Ireland provide a well-constrained and correlatable stratigraphy which defines a sequence of sub-reclined, tight-isoclinal Caledonian (c. 460 Ma) fold nappes. Within this fold complex, the dominant structure is the crustal-scale Ballybofey Nappe, which may be traced for 40 km along strike and is responsible for a regional (500 km2) stratigraphie inversion. The gentle, NE-plunging attitude of this fold results in a complete spectrum of tectonic levels and deformation gradients being exposed. Relatively low strains in the upper fold limb gradually increase down through the nappe, resulting in the generation of composite foliations and lineations and the development of a 10 km thick shear zone which culminates in a high strain basal detachment with underlying pre-Caledonian basement. The Ballybofey Nappe nucleated and propagated along a major zone of lateral sedimentary facies variation, coincident with the margin of a major Dalradian sub-basin. The large amplitude of the nappe is strongly influenced by the lateral heterogeneity within the metasedimentary sequence, and is associated with a minimum of 25–30 km ESE-directed translation concentrated within the overturned limb. Additional significant displacement is also focused along the basal décollement. Generation of the nappe complex resulted in significant crustal thickening and amphibolite facies metamorphism consistent with 15–18 km of burial, induced by a sequence of nappes propagating in the direction of overshear. The ESE-directed translation of the major fold nappes is away from the Caledonian foreland and a gravity-driven mechanism of nappe emplacement is suggested. Rigorous structural analysis within the cohesive stratigraphie framework enables relationships between the tectonic evolution and stratigraphic patterns to be distinguished, thus allowing models of fold nappe generation and mid-crustal deformation to be evaluated.
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Hess, Aaron M., and Christopher R. Fielding. "Analysis of coastal-plain fluvial architecture and high-frequency stacking patterns in the Upper Cretaceous Masuk Formation, Utah, U.S.A.: Climate-driven cyclicity?" Journal of Sedimentary Research 90, no. 10 (October 1, 2020): 1265–85. http://dx.doi.org/10.2110/jsr.2020.63.
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ABSTRACT Most sequence stratigraphic models are based on the premise that relative changes in sea level (RSL) control stacking patterns in continental-margin settings. An alternative hypothesis, however, is that upstream factors, notably variations in relative water discharge (RQW) or the ratio of water to sediment discharge can influence or control stratal stacking patterns in fluvial systems. Sequence boundaries of RQW-driven systems differ from those driven by base-level fluctuations in that: 1) the depth of incision increases updip, and 2) rates of erosion are spatially uniform, leading to the formation of widespread, planar sequence boundaries. This paper presents an architectural and stratigraphic analysis of the well-exposed Masuk Formation of the Henry Mountains Syncline in southern Utah, an Upper Cretaceous coastal-plain fluvial succession that is interpreted to have been influenced significantly by RQW. Six lithofacies are recognized, three (Facies 1–3) recording floodbasin, mire, and (in one short interval) estuarine environments, and three (Facies 4–6) record different kinds of channel fills on a coastal alluvial plain. Seven major composite channel bodies (Facies 4–6), separated by intervals of non-channel deposits (Facies 1–3), are recognized in the stratigraphic interval. Composite channel bodies display planar, sheet-like geometry and are laterally continuous to a significantly greater extent (> 10 km) than would be expected from purely autogenic channel-belt construction. Together, these intervals record a series of high-frequency sequences, formed along the western margin of the Western Interior Seaway. In each individual sequence is a repetitive facies succession from a basal chaotic sandstone with admixed mudrock and sandstone transitioning upward to a more organized cross-bedded and stratified sandstone. This is interpreted to record cyclical changes from a peaked (flashy) discharge regime to a more normal runoff regime. Paleoflow data indicate a dominance of transverse (eastward-directed) dispersal early in the accumulation of the Masuk Formation, shifting to a pattern of greater axial (northward) dispersal over time. The RQW signal is strong in the lower part of the formation, decreasing upward. This suggests that the relatively short-headed streams draining from the rising Sevier fold–thrust belt were strongly influenced by climatic cyclicity, whereas more distally sourced systems were not. This study provides new insights into the architecture and stacking patterns of coastal-plain fluvial successions, emphasizing the plausible role that climate can play in shaping alluvial architecture in the rock record.
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Walker, R. G. "Facies modeling and sequence stratigraphy." Journal of Sedimentary Research 60, no. 5 (September 1, 1990): 777–86. http://dx.doi.org/10.1306/212f926e-2b24-11d7-8648000102c1865d.
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Washington, P. A., S. A. Chisick, R. W. Dalrymple, B. A. Zaitlin, and R. Boyd. "Estuarine facies models; conceptual basis and stratigraphic implications; discussion and reply." Journal of Sedimentary Research 64, no. 1b (February 15, 1994): 74–77. http://dx.doi.org/10.1306/d4267f50-2b26-11d7-8648000102c1865d.
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Zhemchugova, Valentina A., Vadim V. Rybalchenko, and Tatiana A. Shardanova. "Sequence-stratigraphic model of the West Siberia Lower Cretaceous." Georesursy 23, no. 2 (May 25, 2021): 179–91. http://dx.doi.org/10.18599/grs.2021.2.18.
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Apparently, conceptual base of the sequence stratigraphy is one of the most acknowledged methodologies in the geological world at the present time for the sedimentary strata structure prediction. It is based on the complex analysis of the seismic, stratigraphic and sedimentary data on the depositional bodies where the structure and facies filling is regulated by the relative sea level changes. The Lower Cretaceous section of the Western Siberia in this regard is the unique object, as it is represented by the full range of the clastic depositional environments – from relatively deep-water to the continental, which are very sensitive to the conditions changes. Sequence-stratigraphic analysis results can be used to complete the pragmatic tasks in the petroleum geology as the analysis is based on the reconstruction of the sedimentogenesis processes in the past, and the understanding of that processes is the key to the generalized depositional model development. This model can be used to create the models, which can be applied to the unique local objects that occur in the Lower Cretaceous section.
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Khomentovsky, V. V. "The Vendian System of Siberia and a standard stratigraphic scale." Geological Magazine 123, no. 4 (July 1986): 333–48. http://dx.doi.org/10.1017/s0016756800033422.
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AbstractIn Siberia Vendian is equated with a Yudoma Complex or Yudomian. Yudomian deposits of the Siberian Platform and adjacent geosynclines differ greatly in facies and thickness. According to the composition and structure of Yudomian deposits, four facies provinces may be recognized on the platform. Local stratigraphic charts for each province are presented and their correlation and possibility to subdivide the Vendian System in Siberia into three horizons or stages are substantiated. The upper stage (Nemakit–Daldyn), on the basis of palaeontological evidence, is in its turn subdivided into two zones: Anabarites trisulcatus and Purella antiqua.The most important Early Baikalian rearrangement is proved to take place around 800±50 Ma. The pre-Vendian (Late Baikalian) movements, though less intensive, make the determination of the Yudomian lower boundary easier.The specific character of Vendian biostratigraphy is discussed involving all groups of the organic remains, that causes the necessity of recognition, subdivision and correlation on the basis of the whole complex of data.The boundary between the Vendian System and the Lower Cambrian Tommotian Stage (in type section) is proved to conform to the base of the Pestrozvet Formation, which divides the A. sunnaginicus and P. antiqua zones.
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Muhlbauer, Jason G., and Christopher M. Fedo. "Architecture of a river-dominated, wave- and tide-influenced, pre-vegetation braid delta: Cambrian middle member of the Wood Canyon Formation, southern Marble Mountains, California, U.S.A." Journal of Sedimentary Research 90, no. 9 (September 1, 2020): 1011–36. http://dx.doi.org/10.2110/jsr.2020.023.
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ABSTRACT Across the Mojave Desert of southeastern California, outcrops of the Cambrian middle member of the Wood Canyon Formation preserve the deposits of pre-vegetation braided-fluvial and braid-delta environments. One 78-meter-thick section in the southern Marble Mountains, documented here through detailed stratigraphic logging, facies analysis, architectural panels based on “Structure-from-Motion” models, and a suite of paleocurrent and accretion-surface measurements, provides insight into the development of a river-dominated, wave- and tide-influenced braid delta at the distal end of a continent-scale braidplain. In contrast to other pre-Devonian braid-delta strata, in which mudrock is largely absent, the greater part of the middle member system contains over 5% mudstone. Four facies associations, FA4–7, constitute the middle member section and represent (in order of stratigraphic height) a braidplain-to-delta transition (FA4), proximal braid delta (FA5), distal braid delta (FA6), and upper braid-delta front (FA7). The 20 meters of braidplain-to-delta transition strata are largely similar to those of fluvial middle member sections, containing approximately 2% mudstone, unimodal north-northwest paleoflow, and vertical, downstream, and downstream-lateral accretion elements representing compound barforms and channel fills. Above, each braid-delta facies association (FA5–7) preserves high-sinuosity paleocurrent indicators, 6–12% mudstone, and symmetrical, wave-formed sand waves. Decimeter-thick fluid-mud deposits found chiefly in FA6 and less commonly in FA7 indicate the presence of a turbidity-maximum zone that records brackish-water conditions in the distal braid delta. Trace fossils concentrated in FA7 suggest that metazoans were confined to the upper braid-delta front and could not tolerate the variable salinity of the braid delta. Increased marine influence with stratigraphic height requires gradual transgression during deposition of the middle member of the Wood Canyon Formation, possibly as part of a lowstand systems tract.
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Hance, Luc, Eddy Poty, and Francois-Xavier Devuyst. "Stratigraphie sequentielle du Dinantien type (Belgique) et correlation avec le Nord de la France (Boulonnais, Avesnois)." Bulletin de la Société Géologique de France 172, no. 4 (July 1, 2001): 411–26. http://dx.doi.org/10.2113/172.4.411.
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Abstract The relative influences of local tectonics and global eustasy in the architecture of the sedimentary units of the Namur-Dinant Basin (southern Belgium) are determined. Nine third-order sequences are recognised. During the Lower Tournaisian (Hastarian and lower Ivorian) a homoclinal ramp extended from southern Belgium through southern England (Mendips) and into southern Ireland. From the upper Ivorian to the lower Visean rapid facies changes occurred due to progradation and increasing prominence of Waulsortian mudmounds. Progradation gradually produced a situation in which inner shelf facies covered the Namur (NSA), Condroz (CSA) and southern Avesnes (ASA) sedimentation areas, whereas outer shelf facies were restricted to the Dinant sedimentation area (DSA). During the middle and late Visean a broad shelf was established from western Germany to southern Ireland. Because the shelf built up mainly by aggradation, parasequences can be followed over a large area. An early phase of Variscan shortening is perceptible during the Livian. The stratigraphic gap between the first Namurian sediments (E2 Goniatite Zone) and the underlying Visean varies from place to place, but is more important in the north.
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Jewuła, Karol, Wiesław Trela, and Anna Fijałkowska-Mader. "The Permian–Triassic boundary in continental sedimentary succession at the SE margin of the Central European Basin (Holy Cross Mountains, Poland)." Geological Magazine 157, no. 11 (March 27, 2020): 1767–80. http://dx.doi.org/10.1017/s0016756820000047.
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AbstractWe studied the upper Permian and Lower Triassic deposits from the northern and northwestern marginal part of the Holy Cross Mountains (SE part of the Central European Basin or CEB, Poland) to examine stratigraphic continuity between these two systems, and to revise the currently existing stratigraphic framework. A previously existing informal lithostratigraphic scheme has been revisited and placed in a broader chronostratigraphic and palaeoenvironmental context. Sedimentary continuity across the Permian–Triassic (P/T) boundary has been confirmed by the presence of Lueckisporites virkkiae Bc morphological norm and Lundbladispora obsoleta–Protohaploxypinus pantii palynomorphs. Facies development reflects an interplay between climatic variations and tectonism during late Permian – Early Triassic time. The P/T boundary was placed between the Siodła Formation and overlying Szczukowice and Jaworzna formations, which coincides with the classical Zechstein–Buntsandstein boundary in the SE part of the CEB. The facies changes recorded in the studied terrestrial succession of the P/T boundary shed light on the environmental dynamic prior, during and after one of the biggest biotic crises in Earth’s history.
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Frey, R. W., and J. D. Howard. "Beaches and beach-related facies, Holocene barrier islands of Georgia." Geological Magazine 125, no. 6 (November 1988): 621–40. http://dx.doi.org/10.1017/s0016756800023438.
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AbstractThe mesotidal coast of Georgia encompasses diverse sedimentary features and depositional environments, most of which typify major facies of the entire Georgia Bight – a broad embayment on the southeastern U.S. shelf. Barrier island strandline environments especially include tidal inlets and shoals, the beach shoreface, foreshore, and backshore, and dunes and washover fans. Low energy beach segments may grade directly into small seaside tidal flats. Relict salt marsh deposits crop out on erosional beaches. All deposits are in dynamic equilibrium with fluctuating coastal conditions and a gradual rise in sea level.Most of these facies are important in interpreting ancient epeiric transgressive/regressive coastal sequences. Pronounced local variations in the overall sequence result from complex latero-vertical relationships between (1) the shoreface, foreshore, and shoals, and (2) the shoals, low energy beaches, and beach-related tidal flats. Washover fans and relict deposits on erosional beaches cause perturbations within present day lateral relationships but are normal in transgressive facies tracts along such coasts. Close stratigraphic control of outcrops or cores would be necessary for detailed reconstructions of, or correlations among, ancient analogs.
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Rijsdijk, K. F., S. Passchier, H. J. T. Weerts, C. Laban, R. J. W. van Leeuwen, and J. H. J. Ebbing. "Revised Upper Cenozoic stratigraphy of the Dutch sector of the North Sea Basin: towards an integrated lithostratigraphic, seismostratigraphic and allostratigraphic approach." Netherlands Journal of Geosciences 84, no. 2 (July 2005): 129–46. http://dx.doi.org/10.1017/s0016774600023015.
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AbstractA revised Upper Cenozoic stratigraphic framework of the Dutch sector of the North Sea Basin is presented whereby offshore stratigraphic units are integrated or correlated with onshore units. The framework is based on an integrated stratigraphic approach that combines elements of lithostratigraphy, seismostratigraphy and allostratigraphy. Offshore formations are redefined in terms of seismofacies and lithofacies associations, and are differentiated on the basis of common genesis and stratigraphic position. These facies associations represent five major depositional environments, which occur in repetitive successions in the subsurface of the Netherlands: Marine, Coastal, Glacial, Fluvial, and Local Terrestrial. Five conceptual basin-wide bounding discontinuities are identified in the North Sea-Basin that span land and sea. They are represented by both seismostratigraphic and lithostratigraphic unconformities and interpreted as surfaces that formed as a result of North Sea Basin-wide changes in depositional systems. Their formation relates to sea level rise, continental-scale glaciations, and tectonic processes. The bounding discontinuities separate informal allostratigraphic groups of formations that have a grossly uniform geologic setting in common. While the allostratigraphic principles provide a view on the stratigraphy on the largest spatial and temporal scale, the genetic concept facilitates mapping on a local scale.
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Torres de la Cruz, Felipe de Jesús, Elizabeth Chacón-Baca, Gabriel Chávez-Cabello, and María Isabel Hernández-Ocaña. "Revisiting the Cupidito unit (Cupido Formation) along peritidal carbonates from northeastern Mexico." Revista Mexicana de Ciencias Geológicas 37, no. 1 (March 31, 2020): 9–25. http://dx.doi.org/10.22201/cgeo.20072902e.2020.1.1095.
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Depositional episodes are readily identified along representative localities of the Lower Cretaceous Cupido platform in northeastern Mexico. The basal part of the Cupido Formation exhibits a progradational reef platform that, at the upper limit, is truncated by a sequence boundary defined by a breccia. This breccia marks the development of a peculiar sedimentary facies informally known as the Cupidito unit, a distinctive stratigraphical unit in northeastern Mexico that remained uninterpreted for decades. Through the analysis of facies, microfacies and stable isotope comparisons from representative localities (Potrero Chico, Potrero de García, La Huasteca, La Muralla and Puerto Mexico) and from other previously reported outcrops, this work describes six diagnostic features for Cupidito and an improved stratigraphic model is proposed. The depositional sequence suggests a broad flat-topped platform with a general low organic productivity and restricted conditions followed by recurrent inundations of lagoon waters. Before drowning, this carbonate platform remained under equilibrium conditions interrupted by short pulses of relative higher-temperatures (48.3 °C and 39.2 °C). Coral-rudist-stromatoporoid patch-reefs with inferred inter-tropical temperatures between 31.5 °C and 32.2 °C originated as a progradational response to the instauration of a new Sequence Boundary at the base of Cupidito.
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Alshammari, Bassam, Nigel P. Mountney, Luca Colombera, and Mohammed A. Al-Masrahy. "Sedimentology and stratigraphic architecture of a fluvial to shallow-marine succession: The Jurassic Dhruma Formation, Saudi Arabia." Journal of Sedimentary Research 91, no. 7 (July 30, 2021): 773–94. http://dx.doi.org/10.2110/jsr.2020.077.
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ABSTRACT The interaction of fluvial, tidal, and wave processes in coastal and paralic environments gives rise to sedimentary successions with highly varied styles of facies architecture; these are determined by the morphology and evolutionary behavior of the range of coastal sub-environments, which may be difficult to diagnose in subsurface sedimentary successions with limited well control. This study presents depositional models to account for stratigraphic complexity in a subsurface fluvial to shallow-marine succession, the Middle Jurassic Dhruma Formation, Saudi Arabia. The study achieves the following: i) it examines and demonstrates sedimentary relationships between various fluvial, nearshore, and shallow-marine deposits, ii) it develops depositional models to account for the stratigraphic complexity inherent in fluvial to shallow-marine successions, and iii) it documents the sedimentology and the stratigraphic evolutionary patterns of the lower Dhruma Formation in the studied area of Saudi Arabia. The dataset comprises facies descriptions of 570 m of core from 14 wells, 77 representative core thin sections, 14 gamma-ray logs, and FMI image logs from 4 wells. These data are integrated with quantitative information from > 50 analogous systems from a wide range of modern and ancient settings, stored in a relational database. Stratigraphic correlations reveal the internal anatomy of the succession. Facies associations are representative of fluvial channels, intertidal flats, pedogenically modified supratidal flats or floodplains, river-influenced tidal bars, weakly storm-affected shoreface and offshore-transition zones, storm-dominated delta-front and prodelta settings, and an open-marine carbonate-dominated shelf. These sub-environments interacted in a complex way through space and time. The vertical succession of the studied interval records an overall transition from coastal-plain deposits at the base to marine deposits at the top. As such, the succession records a long-term transgressive, deepening-upward trend. However, this general trend is punctuated by repeated progradational events whereby coastal sand bodies of fluvial, wave, and tidal origin prograded basinward during stillstands to fill bays along a coastline. The nature of juxtaposition of neighboring sub-environments has resulted in a sedimentary record that is highly complex compared to that generated by morphologically simple shoreface systems that accumulate more regularly ordered stratal packages.
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Tinterri, Roberto, and Andrea Civa. "Laterally accreted deposits in low efficiency turbidites associated with a structurally-induced topography (Oligocene Molare Group, Tertiary Piedmont Basin, NW Italy)." Journal of Sedimentary Research 91, no. 7 (July 19, 2021): 751–72. http://dx.doi.org/10.2110/jsr.2020.174.
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ABSTRACT The origin of laterally accreted deposits in ancient deep marine successions is often controversial. Indeed, not always do these features imply the occurrence of meanders or high-sinuosity turbidite channels, but they can be generated by other causes, such as sediment-gravity-flow dynamics controlled by the morphology of tectonically confined mini-basins. This work discusses laterally accreted deposits composed of sharp-based, normally graded beds in a very small tectonically controlled mini-basin. These beds, characterized by a well-defined asymmetrical cross-current facies tract, form well-developed lateral-accretion surfaces dipping in directions ranging between W and SW, and perpendicular to the paleocurrents directed towards the N. For this reason, these deposits have always been interpreted as point bars related to meandering channels. A new detailed stratigraphic framework and facies analysis have led to an alternative interpretation, namely that these deposits record lateral deflections of small volume, longitudinally segregated turbidite dense flows against a structurally controlled morphological high. This interpretation is also supported by a comparison to other tectonically controlled turbidite systems that are characterized by higher degrees of efficiency but show similar laterally accreted deposits and cross-current facies tracts.
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Borer, James. "High-Resolution Stratigraphy of the lower portion of the Green River Formation at Raven Ridge and Red Wash Field, NE Uinta Basin, Utah, Colorado, USA: Facies and Stratigraphic Patterns in a High-Gradient, High-Energy Lacustrine System." Mountain Geologist 53, no. 3 (July 2016): 119–223. http://dx.doi.org/10.31582/rmag.mg.53.3.119.
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Lacustrine strata of a portion of the Green River Formation studied in outcrops along Raven Ridge and in the subsurface around Red Wash Field in the northeastern Uinta Basin represent cyclic storm-dominated shoreface to deep lake deposition within a syntectonic embayment on the margin of Eocene Lake Uinta. The study interval consists of the lower Green River Formation, including the Douglas Creek, Garden Gulch, and lower Parachute Creek members, from the top of the underlying Wasatch to the Mahogany Zone of the Parachute Creek Member. Data consists of 11,900 ft (3627 m) of section measured at 23 locations across Raven Ridge, including 7,800 ft (2377 m) of hand-held gamma-ray scintillometer measurements, and over 500 wells in the greater Red Wash Field area, including pay zone analysis correlated to stratigraphy in the field. Facies analysis, as the basis for an integrated stratigraphic approach, reveals a seven-fold hierarchy of stratigraphic cycles ranging from two orders of large-scale cycles to five orders of progressively higher-frequency (smaller scale) shoreface-lake cycles across an 18-mile (29 km) long and 1900-ft (579 m) thick dip-oriented stratigraphic transect. This study recognized twenty-two facies grouped into eight facies tracts using Walther’s Law for two composite shoreface successions: one for a siliciclastic storm-graded shoreface profile that was dominant during times of regression and one for a carbonate profile that dominated in times of transgression. Two important regional facies trends across Raven Ridge include: 1) greater proportions of mudstone facies present in the southern, upper portion of the Green River Formation; and 2) significantly higher proportion of bioturbated sandstone in the northern, lower portion of the formation. The long-term 2nd-order transgression of Lake Uinta from base to top of the study interval results in an evolution from a low-gradient shoreline with marshes, ponds, and sand/mud flats to a high-gradient high-energy profile composed of spits and shorefaces that grew southward away from the emergent highlands. A composite storm-graded shelf profile shows how trough, hummocky, and swaley cross stratification type and amalgamation style change offshore proportionally to contain mud-dominated tempestites, erosional storm furrows, and oil shale. In the most offshore positions, diastasis cracks caused by differential loading are common. The lacustrine shoreface profile is compressed in the Green River Fm. in the study area with narrow facies tracts and large local gradient changes as a result of different responses to sediment supply. As a lake grows and shorelines migrate, the increase in accommodation is balanced, or in-phase, by a corresponding increase in sediment supply resulting in shoreface progradation keeping up with lake-level rise. As the shoreface stacks vertically during the rise, over steepening and failure of the profile generates gravity-flow sandstone facies. Little reworking of hummocky cross stratification high on the profile was observed, probably because wave power was limited by a shallow fair-weather wave-base. These differences also result in more symmetrical lacustrine shoreface cycles, with a large proportion of sediment partitioned into rise hemicycles, as opposed to the classical fall-asymmetric marine para-sequence which tends to have little to no strata preserved in the rise hemicycle along most of the shoreface profile. Landward-stepping lacustrine shoreface cycles are more common during the early rise portions of larger-scale 3rd-order megacycles for similar reasons. Strata at Raven Ridge support the concept that Eocene Lake Uinta was chemically stratified, or meromictic, at least during certain periods. The equable subtropical Eocene paleoclimate is interpreted to be the most important control on meromixis. Chemical stratification played a critical role in the development and preservation of organic matter, as evidenced by oil shale facies. The equable climate, however, might also have made the lake prone to thermal stratification. A paradox exists in the storm dominance of the lacustrine shorefaces and the coeval lake stratification: wave energy apparently was insufficient to break through the strong chemocline. Red Wash Field, directly downdip from the Raven Ridge outcrop belt, is an example of an oil field in a setting where the lake margin is not coincident with a structural feature: a “non-coincident” margin. Reservoirs mostly are present in the 6th-order aggradational shoreface cycles that are interpreted to have accumulated in the rise portions of 3rd-order megacycles. The best reservoir facies are trough, hummocky, and swaley cross-stratified sandstone deposited by storm processes and structureless sandstone probably derived from over steepening and failure of the shoreface during transgression. A petroleum accumulation model encompassing the Red Wash-Raven Ridge area proposes that lacustrine-sourced petroleum originated from an over-pressured mature cell in the Altamont-Bluebell field region. Oil migrated updip through leaky seals and became trapped in reservoirs within the non-coincident lake margin strata. An irregular shoreline configuration and compaction folds at Red Wash Field trapped petroleum. After reaching spill point at Red Wash Field, oil migrated farther updip to Raven Ridge and Asphalt Ridge, forming tar sand accumulations.
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Reading, Harold G. "Clastic facies models, a personal perspective." Bulletin of the Geological Society of Denmark 48 (December 31, 2001): 101–15. http://dx.doi.org/10.37570/bgsd-2001-48-05.
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Facies models evolved from classifications that were mainly descriptive, based on observable, measureable features such as the composition and texture of sedimentary rocks. As our understanding of sedimentary processes expanded, genetic facies models were developed based on the inferred process of formation. Since individual facies cannot be interpreted in isolation, they must be studied with reference to their neighbours, emphasizing the association of facies and sequences, in particular those that coarsen and fine upward. Environmental facies models are based on the interaction of studies on modern environments and ancient rock facies. Earlier facies models tended to invoke intrinsic, autocyclic controls. The advent of sequence stratigraphy led to greater emphasis on the surfaces that separate sequences and to external allocyclic controls. These were, initially, sea-level changes; later, changes in climate, tectonic movements and sediment supply were invoked. Over time, simple, all embracing models have given way to increasingly complex ones as our knowledge of the variability of nature has increased. Complex though these models are, they are only simplifications of reality. In nature there are no models and the majority of past environments differed in some respect from any modern environment. Each environment and rock sequence is unique.
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La Fontaine, Nathan, and Michael Hofmann. "Quantifying the stratigraphic and spatial facies distribution in an ancient mixed-influence delta." Mountain Geologist 56, no. 1 (February 2019): 19–44. http://dx.doi.org/10.31582/rmag.mg.56.1.19.
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Analysis of the sedimentology and stratigraphic architecture of tightly spaced three dimensional outcrops reveals that the Turonian (Upper Cretaceous) Wall Creek Member of the Frontier Formation in the western Powder River Basin, Wyoming, USA, is not composed of one continuous coarsening upward succession but of a complex stacked delta system containing three distinct sequences (S1-S3), each with a unique facies distribution and architectural heterogeneity. The basal sequence S1 consists of a fluvial dominated delta with two distinct lobes. These lobes are spatially constrained to the northeastern study area and show a rapid facies transition from trough crossbedded mouthbar deposits to lower delta front turbidites. Low angle clinoforms suggest a low accommodation setting with main sediment transport to the south. The middle S2 sequence is common throughout the study area and contains an abundance of storm-derived deposits, including hummocky cross stratification, suggesting the transition to a wave and storm-dominated delta setting. Sediment transport is largely to the south controlled by wind induced shear stresses. Lastly, heterolithic trough crossbedded sandstones with flaser bedding and abundant thin mudstones and rip-up clasts are characteristic for sequence S3. These deposits are interpreted as tidal bars in a tidal influenced delta. Quantitative evaluation of facies in the Wall Creek Member sequences shows that the dimensions and connectivity (baffle or barrier competence) of fine-grained thin beds varies systematically within the three delta types. The S1 fluvial delta is largely composed of laterally continuous delta front turbidites with continuous fine-grained thin beds (mean length 21.1 m or 69.2 ft, max length 83.9 m or 275.2 ft) separating individual sandstone beds. Conversely, abundant bioturbation and intense scouring by storms results in high amalgamation of sandy beds in sequence S2 and a limited length of fine-grained thin beds (mean 8.5 m or 27.9 ft) in the wave-dominated delta sequence. Tidally influenced deposits of sequence S3 are largely composed of heterolithic trough crossbedded sandstones and mudstones with low bioturbation, resulting in an intermediate fine-grained thin bed deposit (mean 12.1 m or 39.7 ft).
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Geyman, Emily C., and Adam C. Maloof. "Facies control on carbonate δ13C on the Great Bahama Bank." Geology 49, no. 9 (May 17, 2021): 1049–54. http://dx.doi.org/10.1130/g48862.1.
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Abstract The carbon isotopic (δ13C) composition of shallow-water carbonates often is interpreted to reflect the δ13C of the global ocean and is used as a proxy for changes in the global carbon cycle. However, local platform processes, in addition to meteoric and marine diagenesis, may decouple carbonate δ13C from that of the global ocean. We present new δ13C measurements of benthic foraminifera, solitary corals, calcifying green algae, ooids, coated grains, and lime mud from the modern Great Bahama Bank. We find that vital effects, cross-shelf seawater chemistry gradients, and meteoric diagenesis produce carbonate with δ13C variability rivaling that of the past two billion years of Earth history. Leveraging Walther's Law, we illustrate how these local δ13C signals can find their way into the stratigraphic record of bulk carbonate.
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Hart, Bruce S. "Whither seismic stratigraphy?" Interpretation 1, no. 1 (August 1, 2013): SA3—SA20. http://dx.doi.org/10.1190/int-2013-0049.1.
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Here, I provide an historical summary of seismic stratigraphy and suggest some potential avenues for future collaborative work between sedimentary geologists and geophysicists. Stratigraphic interpretations based on reflection geometry- or shape-based approaches have been used to reconstruct depositional histories and to make qualitative and (sometimes) quantitative predictions of rock physical properties since at least the mid-1970s. This is the seismic stratigraphy that is usually practiced by geology-focused interpreters. First applied to 2D seismic data, interest in seismic stratigraphy was reinvigorated by the development of seismic geomorphology on 3D volumes. This type of reflection geometry/shape-based interpretation strategy is a fairly mature science that includes seismic sequence analysis, seismic facies analysis, reflection character analysis, and seismic geomorphology. Rock property predictions based on seismic stratigraphic interpretations usually are qualitative, and reflection geometries commonly may permit more than one interpretation. Two geophysics-based approaches, practiced for nearly the same length of time as seismic stratigraphy, have yet to gain widespread adoption by geologic interpreters even though they have much potential application. The first is the use of seismic attributes for “feature detection,” i.e., helping interpreters to identify stratigraphic bodies that are not readily detected in conventional amplitude displays. The second involves rock property (lithology, porosity, etc.) predictions from various inversion methods or seismic attribute analyses. Stratigraphers can help quality check the results and learn about relationships between depositional features and lithologic properties of interest. Stratigraphers also can contribute to a better seismic analysis by helping to define the effects of “stratigraphy” (e.g., laminations, porosity, bedding) on rock properties and seismic responses. These and other seismic-related pursuits would benefit from enhanced collaboration between sedimentary geologists and geophysicists.
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Wilson, A. O. "Chapter 7 Exploration implications." Geological Society, London, Memoirs 53, no. 1 (2020): 187–96. http://dx.doi.org/10.1144/m53.7.
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AbstractExploration of the Jurassic hydrocarbon system in the Arabian Intrashelf Basin area is in a mature state. Given the scale of the present day anticlinal structures and the adjacent synclines, all of the supergiant conventional fields trapped in huge anticlines have already been discovered. The theme throughout this Memoir has been to present the evolution of the self-contained Callovian–Tithonian Arabian Intrashelf Basin hydrocarbon system. Its size, c. 1200 × 450 km, is greater than that of the UK, larger than the Black Sea and almost as large as Turkey or the area of Texas and New Mexico in the USA. It is geologically much simpler than these regions, both in the exceptionally remarkable continuity of facies within the sequences that developed and filled the intrashelf basin and its relative tectonic simplicity, including up to the present day. The cross-sections, facies maps, depositional profiles and other data and interpretations presented in this Memoir have documented this remarkable continuity. The source rock interval is well-defined everywhere it occurs and is mature; enough oil has been generated and migrated so that every sealed trap with reservoir facies will have oil. Around and within the basin, shallow water ramp facies in each sequence are in the reservoir facies and the early-formed porosity has been preserved. The carbonate seals and, even more so, the evaporite seals are remarkably laterally continuous. Therefore the big issue in future exploration is finding a sealed trap with potential reserves large enough to be worth drilling when compared to known reserves and estimates of future production. This chapter discusses some possibilities for stratigraphic traps and unconventional plays. Potential plays have been and/or can be identified, but finding them in the present day structural setting is likely to be very difficult.
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Pattison, Simon A. J. "High resolution linkage of channel-coastal plain and shallow marine facies belts, Desert Member to Lower Castlegate Sandstone stratigraphic interval, Book Cliffs, Utah-Colorado, USA." GSA Bulletin 131, no. 9-10 (April 15, 2019): 1643–72. http://dx.doi.org/10.1130/b35094.1.
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AbstractThe Campanian Desert Member and Lower Castlegate Sandstone in the Book Cliffs of east-central Utah to western Colorado, USA, has served as a foundational data set in the development of sequence stratigraphy. Contrary to previous work, no third-order sequence boundaries are recognized. These were originally thought to partition the neighboring coastal plain and shallow marine facies belts into separate systems tracts, unlinked in time or space. In contrast, adjoining channel-coastal plain and shallow marine facies belts are genetically-, temporally-, and spatially-related. Evidence includes the (i) synchronous, strongly progradational stacking patterns within each facies belt, (ii) gradational and conformable transitions between adjoining facies belts, accentuated by the ubiquity of flat-topped, rooted foreshore sandstones passing upwards into carbonaceous-rich-mudstone-dominated coastal plain, (iii) parasequence-scale interfingering of coastal plain-channel and foreshore-shoreface deposits, with channels, white caps and coals embedded within stacked shoreface parasequences, (iv) regional correlation of coals and flooding surfaces, and (v) near orthogonal paleocurrent relationship between channels and shorelines. Terminal channels incise into proximal foreshore-shoreface sandstones in most Desert-Castlegate parasequences. Incisions are generally confined to the parasequence in which the channels are nested, rarely cutting deeper. These shoreface-incised channels are cut and filled at a parasequence-scale, and are bounded above by the same flooding surface that caps each foreshore-shoreface package. The ubiquity of ascending regressive shoreface trajectories and near absence of descending regressive trajectories that intersect depositional slope argues against any significant sea level fall. Increased rates of sediment supply, driven by autogenic and/or allogenic processes, likely generated the strongly progradational Desert-Castlegate great tongue of sandstone.
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Liu, Deng, and Dai Yong Cao. "Regional Geology Background and Minerogenetic Series in Ongniud Banner of Inner Mongolia." Advanced Materials Research 734-737 (August 2013): 408–17. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.408.
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Ongniud Banner is located in the northern margin of the North China platform, possessing binary attribute of the greenville period orogenic belt and North China block. The authors reclassify geological unit through the rock stratigraphic correlation and isotope chronology. Achaean strata is mainly composed of quartz schist, chlorite schist, amphibole schist, and the rocks have been highly metamorphosed into the green schist facies, and its single particle zircon U-Pb age is 2645 ±86Ma, so it is assigned to North China block. Proterozoic strata is mainly composed of metamorphic complex including chlorite schist, marble, basalt, amphibolite, plagiogranite and olivine pyroxenolite, and its single particle zircon U-Pb age is 1620±160Ma, so it is assigned to Greenville period orogenic belt. According to 1:50000 stream sediment geochemical elementary assemblage characteristics, the authors discuss the metallogenic endowment and minerogenetic series of geological unit in research area.
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Lindsay, J. F., M. D. Brasier, G. Shields, V. V. Khomentovsky, and Y. A. Bat-Ireedui. "Glacial facies associations in a Neoproterozoic back-arc setting, Zavkhan Basin, western Mongolia." Geological Magazine 133, no. 4 (July 1996): 391–402. http://dx.doi.org/10.1017/s0016756800007561.
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AbstractDiamictites, many of glacial origin, are globally distributed in the Neoproterozoic. Recently, two relatively thin diamictites in the Maikhan Uul Member at the base of the Neoproterozoic Tsagaan Oloom Formation from the Zavkhan Basin of western Mongolia have been identified as being of glacial origin. The Mongolian diamictites form a series of backstepping units within the transgressive systems tract of two major depositional sequences associated with sea-level changes. In each case the diamictites of the transgressive systems tract are abruptly overlain by deeper water, upward shoaling highstand systems tracts consisting of thinly bedded sandstones and shales in sequence 1 and thinly bedded, dark carbonates in sequence 3. The fact that the sequences conform closely to depositional models established at other localities suggests that all are related to major ice ages and that the depositional sequences they have generated provide a valuable tool for global correlation in this part of the stratigraphic column. Available stratigraphic and isotope geochemical information presented by Brasier et al. (1996, this issue) suggests that both diamictites are likely to be of Sturtian age. A riftogenic setting and Sturtian age for the diamictites provide a link with eastern Australia and western America. It is possible, therefore, that these diamictites formed during the breakup of a supercontinental assembly including Siberia, Australia and Laurentia c. 750–725 Ma BP.
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Vuillemin, Aurèle, Mapathe Ndiaye, Rossana Martini, and Eric Davaud. "Cement stratigraphy: image probes of cathodoluminescent facies." Swiss Journal of Geosciences 104, no. 1 (February 15, 2011): 55–66. http://dx.doi.org/10.1007/s00015-010-0047-8.
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Larena, Z., C. Arenas, J. I. Baceta, X. Murelaga, and O. Suarez-Hernando. "Stratigraphy and sedimentology of distal-alluvial and lacustrine deposits of the western-central Ebro Basin (NE Iberia) reflecting the onset of the middle Miocene Climatic Optimum." Geologica Acta 18 (May 20, 2020): 1–26. http://dx.doi.org/10.1344/geologicaacta2020.18.7.
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Stratigraphic and sedimentological study of distal alluvial and lacustrine deposits in the Plana de la Negra-Sancho Abarca area (western-central Ebro Basin, NE Iberia) within the early and middle Miocene allows five main lithofacies to be characterized and mapped within two tectosedimentary units, construction of a sedimentary facies model and discussion on allogenic controls on sedimentation. In this area, the boundary between tectosedimentary units T5 and T6 appears to be conformable and is marked by the change from dominant clastics to carbonates. Correlation of the studied outcrops with nearby sections that already had magnetostratigraphic and biostratigraphic data allows the studied succession to be dated from C5Dr to C5Cn (Burdigalian-Langhian), placing the boundary T5/T6 at ca. 16.1-16.05Ma. Seven vertical facies sequences document deposition of distal alluvial clastics and palustrine and lacustrine carbonates. Sandstones and mudstones represent low-sinuosity channels and lateral and terminal splays by unconfined flows runnig across the alluvial plain, associated to the Pyrenean-derived Luna fluvial system. The carbonates contain charophytes, ostracods, bivalves and gastropods, indicating deposition in 2-4m deep lakes. Laminated carbonate facies record reworking of shore carbonates and the influx fine-siliciclastic sediment offshore. Abundant bioturbation and desiccation features indicate episodic submergence and subaerial exposure. Four main episodes of alluvial and associated palustrine/lacustrine facies belt shifts are identified. Alluvial deposition in the studied T5 unit is related to low lake level conditions, rather than to a Pyrenean uplift. The maximum extent of the freshwater carbonates occur at the base of unit T6. This is consistent with conditions of increasing humidity of the Middle Miocene Climatic Optimum.
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Yalçin, M., and Isak Yilmaz. "Devonian in Turkey — a review." Geologica Carpathica 61, no. 3 (June 1, 2010): 235–53. http://dx.doi.org/10.2478/v10096-010-0014-3.
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Devonian in Turkey — a reviewThe Devonian Period is represented in Turkey by almost complete non-metamorphic sections of more than 1000 meters, which exhibit varying lithofacial associations. They are parts of thick Paleozoic sedimentary successions in the Pontides, Taurides and Arabian Plate. The tectonic setting and the paleogeographical origin of these terranes is different. Therefore, the litho- and biostratigraphy and facies characteristics of these Devonian successions would enable a comparison and a paleogeographical assignment of these tectono-stratigraphic units. Devonian successions of the Arabian Plate and of the Taurides are represented by facies associations ranging from tidal flat to a deep shelf. Whereas, those of the Istanbul and Çamdağ-Zonguldak areas in the Pontides by a deepening upward sequence from a shallow shelf into a basin and a stable shelf, respectively. The Devonian of the Arabian Plate and the Taurides can surely be assigned to Gondwana. A Peri-Gondwanan (Avalonian) setting is suggested for the paleogeographic position of the Devonian of the Pontides.
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PAZ, J. D. S., and D. F. ROSSETTI. "Linking lacustrine cycles with syn-sedimentary tectonic episodes: an example from the Codó Formation (late Aptian), northeastern Brazil." Geological Magazine 142, no. 3 (May 2005): 269–85. http://dx.doi.org/10.1017/s0016756805000488.
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The Codó Formation exposed in the eastern Grajaú Basin, northeastern Brazil, consists mostly of black shales, limestones and evaporites arranged into several shallowing-upward cycles formed by progradation of lake deposits. Three ranks of cycles are distinguished. The lower-rank cycles correspond to millimetric interbeddings of: bituminous black shales with evaporites, calcimudstones or peloidal wackestone–packstone; grey/green shale with calcimudstone, peloidal wackestone–packstone or ostracodal wackestone/grainstone; and ostracodal wackestone/grainstone and/or calcimudstones with cryptomicrobial mats and ooidal/pisoidal packstones. The intermediate-rank cycles average 1.7 m in thickness and are formed by complete and incomplete cycles. Complete cycles show a transition from central to intermediate and then to marginal facies associations and include two types: C1 cycle with central lake deposits consisting of evaporites and black shales; and C2 cycle with central lake deposits formed by grey/green shale. Complete cycles were produced by the upward gradation from central to marginal environments of the lake or saline pan–sabkha system. Incomplete cycles are those where at least one facies association is lacking, having been formed by successions either with central and intermediate facies associations (I1) or intermediate and marginal facies associations (I2). The higher-rank cycles are, on average, 5.2 m thick and consist of four depositional units that display shallowing-upward successions formed by complete and incomplete intermediate-rank cycles that vary their distribution upward in the section, and are bounded by sharp surfaces. While the lower-rank cycles display characteristics that reveal their seasonal signature, detailed sedimentological characterization and understanding of stratal stacking patterns related to the intermediate and higher-rank cycles support a genesis linked to syn-sedimentary tectonic activity. This is particularly suggested by the high facies variability, limited lateral extension, and frequent and random thickness changes of the intermediate-rank cycles. Additionally, the four higher-rank cycles recognized in the Codó Formation match with stratigraphic zones having different styles of soft-sediment deformation structures attributed to seismic activities. Therefore, the several episodes of lake shallowing recorded in the Codó Formation are linked to seismic pulses that alternated with sediment deposition. This process would have created significant changes in the lake water level and resulted in sharply bounded successions with upward gradation from deeper to relatively shallower facies associations.
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Sharpe, David R., and Peter J. Barnett. "Significance of Sedimentological Studies on the Wisconsinan Stratigraphy of Southern Ontario." Géographie physique et Quaternaire 39, no. 3 (December 4, 2007): 255–73. http://dx.doi.org/10.7202/032607ar.
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ABSTRACTDetailed facies mapping along Lake Erie and Lake Ontario Bluffs, plus other studies illustrate that sedimentological studies, especially those with geomorphic or landform control, have had three main effects on the Wisconsinan stratigraphy of Ontario: (1) improved understanding of depositional processes and environments of several major rock stratigraphic units, without altering the stratigraphic framework, (2) aided correlation of drift sequences, and (3) questioned previous interpretations and stratigraphic correlations of drift sequences. Thus sedimentological analysis can not be separated from stratigraphy because the interpretation of depositional environnments of many mapped strata relies on their geometry and the inclusion of regional data. The geomorphic control provided by sedimentological study of surface landforms is also important because assessment of older buried sediments such as those at the Scarborough Bluffs has been hampered by the failure to determine landform control. The Late Wisconsinan stratigraphy of Southern Ontario generally remains unchanged, except for questions on the role of climate versus ice margin dynamics. The pre-Late Wisconsinan stratigraphy is scarce and not well defined, yet sedimentary studies support the presence of glacial ice in the Ontario Lake basin for all of the Middle Wisconsinan and possibly earlier, including the formation of the Scarborough delta. Large channel cut and fill sequences in the Toronto area (Pottery Road Formation), initially interpreted as resulting from subaerial erosion, were probably formed by subaqueous or subglacial meltwater erosion. If so, the pre-Late Wisconsinan stratigraphy in southern Ontario changes because the Pottery Road Formation may not be an Early Wisconsinan correlative of the St. Pierre beds. The channel example illustrates that stratigraphie correlation without sedimentological investigations may be misleading.
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Yan, Bai Quan, Er Shuang Gao, Dan Dan Peng, Xiao Lei Tian, and Guang Wang. "Sedimentary Microfacies Analysis of S II Reservoir Group in the Block X of Daqing Oil Field." Advanced Materials Research 616-618 (December 2012): 170–73. http://dx.doi.org/10.4028/www.scientific.net/amr.616-618.170.
Full textAbstract:
With the continuous and deepening development of oil field, reseach of sedimentary microfacies is more and more important on the basis of energy facies. The study area is the thin oil thermal recovery experimental zone of Daqing Oilfield. A variety of microfacies boundary has strong resistant and limiting effect for the filterring flow characteristics of underground fluid. This study is based on the fine contrast to reservoir, establish high resolution sequence stratigraphic framework, set up the logging facies mode of different levels of the energy levels on the basis, make the logging facies identification and combination of space for 17 sedimentary time units of SⅡ reservoir group by well to well and layer to layer, portray fine 17 sedimentary time units of the spatial distribution characteristics of sedimentary microfacies, and provid the scient geology-orientation for subsequent thermal recovery program and development effectiveness evaluation.