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Strogen, Dominic Paul. "Diagenesis of Middle to Upper Jurassic sandstones, East Greenland." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323408.
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Carter, Elizabeth Sibbald. "Early and middle Jurassic Radiolarian biostratigraphy, Queen Charlotte Islands, B.C." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24586.
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Radiolarian biostratigraphy is used to construct an informal zonation for sediments of upper Pliensbachian to lower Bajocian age from the Maude and Yakoun Formations, Queen Charlotte Islands, B.C. Paleoenvironmental studies assess depositional environment and the effects of changing facies relationships on the fauna.
Seven distinctive assemblages are recognized comprising 167 species of spumellarian and nassellarian Radiolaria. The first well established middle Toarcian radiolarian assemblages are documented and both these and upper Toarcian assemblages are highly diverse and contain many new and unusual forms. Five genera and 89 new species are described many of which have restricted biostratigraphic ranges. A chlorophyte algal cyst appearing in all lowest Bajocian samples may, with further study, prove to be a significant marker for the lower Bajocian in the Queen Charlotte Islands.
Although Toarcian Radiolaria have been little studied, the assemblages compare with others from North America, the Mediterranean and Japan, and are distinctly Tethyan in aspect. This is consistent with the position of Wrangellia, which paleomagnetic and ammonite biogeographic evidence indicates was in the northern hemisphere within 30° of the equator during the Early to Middle Jurassic.
Studies of the abundance of spumellarians vs. nassellarians indicate thatnassellarians predominate, are abundant and diverse in deeper-water deposits (middle Toarcian and lower Bajocian shales) whereas spume Marians, particularly those with multi-layered or spongy tests, dominate in shallow-water deposits (upper middle Toarcian to Aalenian sandstones). Shallow-water nassellarians are much less diverse but a few species (all multicyrtids with thickened tests) are very abundant. Depth appears to be the major factor controlling radiolarian distribution patterns in this relatively shallow-water setting.
Studies of eustatic sea-level changes throughout the Jurassic have indicated that major phases of sea-level rise occurred in the early to mid Toarcian and in the early Bajocian with a major phase of sea-level lowering in the late Toarcian to Aalenian; detailed study of the radiolarian faunal succession in the Queen Charlotte Islands appears to confirm this major worldwide trend.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate
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Vincent, Alastair James. "Palynofacies analysis of middle Jurassic sediments from the Inner Hebrides." Thesis, University of Newcastle Upon Tyne, 1995. http://hdl.handle.net/10443/979.
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A quantitative palynofacies study of thermally immature Middle Jurassic sediments of Skye, Raasay, and Eigg has been undertaken in order to examine kerogen and palynomorph distributions in relation to various potential controlling factors (lithology, lithofacies, depositional environment, sequence stratigraphy). This has involved performing rigorous kerogen and palynomorph counts on 440 samples from 12 localities (average sampling density 5 per metre in sampled sections), supported by 250 TOC and 57'Rock-Eval' pyrolysis analyses. The facies of the Middle Jurassic sediments of the Inner Hebrides range from subtidal marine to freshwater alluvial mudflats. The succession is divided into three major units: the Bearreraig Sandstone Formation (Aalenian-Bajocian) which is 400m thick, and represents the deposition of tidalsubtidal sand sheets, the ? Bathonian Great Estuarine Group (250m thick) which represents a range of mostly lagoonal-deltaic freshwater to hypersaline facies, and finally the Staffin Bay Formation (lowermiddle Callovian; thickness 18m) which represents a transgressive lagoon-barrier bar complex. ... The detailed subdivision of the phytoclast group has permitted the calculation of a phytoclast preservation index (PPI) which summarises the overall degradation state of the phytoclast assemblage for each sample. The highest PPI values (= most refractory phytoclast assemblagesa) re found in the mudflat-alluvial facies of the Skudiburgh Formation, lowest PPI values, reflecting 'fresh' phytoclast input, are found in the transgressive Staffin Bay Formation. The TOC values are generally <2.5%, but reach up to 3-4% in parts of the Dun Caan Shales Member (Bearreraig Sandstone Formation) and the Lonfearn Member (Lealt Shales Formation), and 6-8% in the Upper Ostrea Member (Staffin Bay Formation). Hydrogen Index (HI) values mostly fall below 300 (organic facies C or CD), but are increased in parts of the Lonfearn and Upper Ostrea members (400- 500, organic facies B), and particularly in the Kilmaluag Formation where values of over 800 are found (= organic facies AB). The correlation between the optical and geochemical data varies from very poor to very good. In some cases TOC is correlated with %AOM, and also %Botryococcus. Multiple regression on the HI suggests that in most cases %AOM is the variable best correlated with the HI; this procedure has allowed the calculation of a predicted HI value for all 440 samples.
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TANAKA, Shiro, Yusei KUROYANAGI, Kazuhiro SUZUKI, and Mamoru ADACHI. "Permo-Triassic and Early-Middle Jurassic granitoid clasts from the Jurassic conglomerates in the Mino terrane, central Japan." Dept. of Earth and Planetary Sciences, Nagoya University, 2002. http://hdl.handle.net/2237/2854.
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Brint, John Forsyth. "Isotope diagenesis and palaeofluid movement : Middle Jurassic Brent sandstones, North Sea." Thesis, University of Strathclyde, 1989. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23310.
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The Middle North Sea, have simplified to a Jurassic deltaic Brent Group sandstones, northern complicated diagenetic sequence which may be kaolinite Fe,Ca carbonates - High porosities and Ness and Tarbert quartz overgrowths - Fe,Mg carbonates - illite. existed in the Etive, throughout diagenesis. By permeabilities have Formation sandstones contrast, the highly micaceous and r,elatively finer grained Rannach Formation sandstones have good porosities but very poor permeabilities due to burial compaction and carbonate cementation. Oxygen and hydrogen isotope studies indicate that early diagenesis occurred in a dominantly meteoric pore water (6180 = -7%0). The early diagenetic cements of siderite, vermicular kaolinite and calcite started to precipitate at 14, 26 and 32DC respectively. With the onset of burial, below 1.2 km, the Brent sequence eventually became sealed off from the meteoric 'head' by Lower Cretaceous sediments. Blocky kaolinite precipitated and by the end Cretaceous quartz overgrowth formation commenced. Fluid inclusions in the overgrowths indicate formation from a warm, dominantly low salinity water (1 - 5 wt.% eq. NaCl). Homogenisation temperatures range from 73to 131 DC. Illite precipitation is cogenetic with the latest stages of quartz overgrowth precipitation (K/Ar illite date, 58Ma.) and has reduced porosity and permeability markedly in different locations prior to oil migration. The depth of burial at which this last cementation event occurred is 2.3 km. Fluid inclusion microthermometry indicates that quartz overgrowth and latest ankerite precipitation occurred in a geothermal gradient of 70DC/km. After this heat excursion the reservoirs have cooled back to present day temperatures of 85 - 11SDC. Water values computed from the mineral cements indicate precipitation from a porefluid which has gradually evolved isotopically to its present day composition (5180 = -7 to +2%.SMOW) in an isotopic system that has become closed during burial. However the quartz and ankerite suggest one unusual episode of open system hot fluid input.
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Norris, Michelle Samantha. "A facies analysis of Middle-Upper Jurassic boundary beds in Europe." Thesis, University of Birmingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539902.
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A facies analysis of Middle-Upper Jurassic boundary beds, i.e. Callovian-Oxfordian Stage boundary beds, has been carried out on numerous sections across Europe, with the aim of constructing relative sea-level curves for each geographic area. Accurate correlation of the various epeiric-sea, sedimentary successions has been achieved using ammonite zonations. The comparison of twelve relative sea-level curves has led to the recognition of regional sea-level events in Europe during the Callovian-Early Oxfordian interval. A regional sea-level rise occurred during the Middle and Late Callovian, reaching its greatest extent in the latest Callovian (lambert; Zone), and highstand conditions and incipient sea-level fall characterized the Early Oxfordian. A literature review of Callovian-Oxfordian boundary beds in six further regions from four other continents has shown that a Middle Callovian sea-level rise and Late Callovian-Early Oxfordian phase of high sea-level can be recognized on a global scale. The European regional sea-level changes are, therefore, considered to be eustatic in origin, and are a response to a third, or possibly second-order, eustatic cycle of 6-1 0 Ma. A "Norris eustatic curve" has been constructed and compared with two published eustatic curves. It differs markedly from that of Hallam (1988), also based on the facies analysis technique, but is very similar to that of Haq el al. (1987), based on sequence stratigraphic concepts. However, the systems tracts and coastal onlap curve of the Haq ct al. (1987) chart are at odds with the facies interpretations made in this study, reflecting the inadequacy of the sequence stratigraphy model in addressing the Jurassic epicontinental sea successions.
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Greenwood, Peter Jeremy. "Diagenesis of Middle Jurassic sandstones and mud rocks, Brae area, North Sea." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294999.
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Ploynoi, Manwika Parcell William C. "Development of middle Jurassic microbial buildups in the Bighorn Basin of northern Wyoming." Diss., A link to full text of this thesis in SOAR, 2007. http://soar.wichita.edu/dspace/handle/10057/1150.
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Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Geology.<br>"May 2007." Title from PDF title page (viewed on Dec. 27, 2007). Thesis adviser: William C. Parcell. Includes bibliographic references (leaves 73-77).
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Corbett, Patrick W. M. "Reservoir characterisation of a laminated sediment : the Rannoch Formation, Middle Jurassic, North Sea." Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1435.
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The probe permeameter is a recently developed device providing a small scale measurement of permeability. About 15,000 probe permeameter measurements were acquired for analysis during this study. These data were acquired by Statoil from cores in two North Sea wells. These cores are from the Middle Iurassic Rannoch Formation of the Brent Group. This reservoir unit was selected for this study because of its laminated nature and challenge to conventional description and simulation practice. All aspects of probe permearnetry are investigated in this study; the volume of investigation, the compatibility with measurements at larger scales, the measurement statistics. the optimum sample spacing. the relationship of the measurements to the geological description and the scale-up of data for two-phase numerical reservoir simulation. Careful analysis of probe and traditional plug data shows that the measurements are compatible. Systematic differences could be accounted for by different treatment effects of the material. The probe measurements show that the permeability distribution in the Rannoch Formation is closely related to the primary depositional structure of the sediment at a hierarchy of scales. This observation is used in combination with conventional simulation techniques to build a more geologically-realistic numerical model of the Rannoch Formation. The scale-up of the small scale measurements is achieved by generation of effective properties for geologically representative elements at various scales and is called the "geopseudo" method. The scale of the natural building blocks within the sediment were determined with the aid of an appropriate outcrop analogue. The model results compare favourably with field production data. This work demonstrates. for the first time. a systematic method for the scale-up of small scale petrophysical properties associated with lamination in sedimentary rocks. as measured by the probe permeameter. Laminated reservoirs are widely encountered and this work. therefore. makes a significant contribution to reservoir engineering practice.
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Noe`, Leslie Francis. "A taxonomic and functional study of the Callovian (Middle Jurassic) Pliosauroidea (Reptilia, Sauropterygia)." Thesis, University of Derby, 2001. http://hdl.handle.net/10545/211770.
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The short-snouted Callovian pliosaurs, Liopleurodon ferox SAUVAGE 1873, Simolestes vorax ANDREWS 1909 and Pachycostasaurus dawni CRUICKSHANK, MARTILL and NOE 1996, of the Peterborough Member, Oxford Clay Formation are of considerable palaeontological importance. The restricted geographical and temporal range, exceptional preservation, relative abundance, and easy removal of matrix, make the Callovian pliosaurs excellent subjects for detailed study. Skull material is known from all Callovianpliosaurs, but has been little studied, and much excellent material remains undescribed. The taxonomy of the short-snouted Callovian pliosaurs is thus in need of critical revision. Cranial functional morphology goes largely undiscussed, and the palaeoecological position of the short-snouted genera is poorly understood. The taxonomy of the short-snouted Callovian pliosaurs is critically revised, and the genera Liopleurodon, Simolestes and Pachycostasaurus shown to be monospecific and taxonomically valid. The holotype material for Liopleurodon ferox is poor (a single tooth) but exhibits sufficient characteristics for taxonomic definition. The holotype material of Simolestes vorax and Pachycostasaurus dawni, an incomplete skull and postcranial skeleton in each case, is taxonomically robust. Never before attempted cranial reconstructions, in multiple views, are presented for each genus. Detailed cranial, mandibular and dental descriptions of Liopleurodon and Simolestes are presented, with description of many new, newly recognised and previously unfigured specimens. The presence of nasals is definitively demonstrated for the first time in any pliosaur genus. The likely presence of a lacrimal in Liopleurodon indicates the relatively plesiomorphic position of the pliosaurs within the Plesiosauria. The skull ofPachycostasaurus is described for the first time, although in less detail than the other two genera due to relatively poor preservation. The teeth of all three genera are described in detail, and a number of new parameters, such as crown stoutness and crown curvature, presented. A comprehensive structural and functional analysis indicates the skull is highly akinetic, and firmly internally braced. The superficial sutural pattern is adapted to resist deformation imposed by muscular action, particularly when feeding. The inference of strongly procumbent teeth in the short-snouted Callovian pliosaurs is shown to be based on the incorrect interpretation of badly crushed specimens. The skull musculature is reconstructed for the first time in a Callovian pliosaur, and an analysis of the lever systems exhibited by the jaws and muscles is presented. The adductor musculature is interpreted as a `geared' system providing mechanical advantage no matter where the teeth strike the prey, rather than the `snap and hold system' previously interpreted in non-Callovian pliosaurs. An analysis of tooth form, preserved stomach contents, and comparison with an existing model allows interpretation of prey preference and ecological position. Liopleurodon, and possibly Pachycostasaurus, are interpreted as shake and bolt feeding, high order predators of large boned, vertebrate prey. Simolestes is reinterpreted as an invertebrate feeder, possibly twist feeding, with a short, wide, high skull and a powerful bite. Comparison is made to the long-snouted genus Peloneustes which is considered ichthyophagous. The potential problems associated with a predominantly invertebrate diet are explored. Simolestes is interpreted as gaining a considerable electrolyte load through a diet of invertebrates. To avoid physiological problems Simolestesp robably possessedla rge, orbitally positioned, cephalic salt secreting glands. All Callovian pliosaur genera probably also possessed salt secreting glands, but of smaller size
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Wakefield, Matthew Ian. "Ostracoda (Crustacea) of the Great Estuarine Group (Bathonian, Middle Jurassic), Inner Hebrides, Scotland." Thesis, University of Leicester, 1991. http://hdl.handle.net/2381/34977.
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The Ostracoda of the Great Estuarine Group, Inner Hebrides, Scotland are monographed. These are referred to Order Podocopida, Suborder Podocopina, superfamilies Cytheracea, Cypridacea and Darwinulacea, seven families, five subfamilies, 17 genera (three new) and 41 species (25 new, 11 in open nomenclature). The stratigraphic occurrence of the ostracod species is determined for the Islands of Skye, Eigg and Muck. The major lithostratigraphic subdivisions of the Great Estuarine Group are reflected in the ostracod fauna. The ostracod species are largely endemic to the Hebrides; there are generic level affinities with other British sequences. Ostracod genera are used to interpret the palaeosalinity of deposition of the Duntulm and Kilmaluag formations. In some cases the palaeosalinity of deposition of individual beds is corroborated using C & O stable isotope analyses. Three salinity controlled ostracod assemblages are recognised and are interpreted to have migrated within the Kilmaluag lagoon due to increased freshwater or brackish-marine water input. By comparison with the associated molluscs, conchostracans and algae, four salinity events are detected within the type section of the Kilmaluag Formation. The Kilmaluag Formation was deposited within shallow, low energy freshwater lagoons with a tenuous link to a water body of brackish-marine salinity producing a salinity gradient. Salinity is the primary control upon faunal and floral occurrences within the Lealt Shale Formation. Relative salinity tolerances are estimated for 26 ostracod species from the formation. Based upon ostracod and mollusc data this formation has rapidly and frequently fluctuating palaeosalinity values. O isotope analyses of the bivalve Praemytilus strathairdensis show a positive correlation with the palaeosalinity fluctuations; the percentage abundances of the alga Botryococcus show a negative correlation. Variations in the adductor muscle-scar rosette of Darwinula muscula are due to the mostly ontogenetic subdivision of scars. Different fossil and Recent species of Darwinula are shown to have different rosette patterns.
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McBride, John J. "The diagenesis of Middle Jurassic reservoir sandstones of Bruce Field, U.K. North Sea." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU045054.
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The earliest volumetrically significant diagenetic phase in the Middle Jurassic reservoir sandstones of Bruce Field (U.K. North Sea) is poikilotopic calcite. Integration of petrographic and isotopic data with burial history modelling indicates that it precipitated from Jurassic sea water at temperatures of about 40oC during the Early Cretaceous at a burial depth of about 600m. Its development was controlled by a favourable combination of many factors: a 'background' of organic-rich, argillaceous and shelly sediments to generate and supply the reactive species by essentially 'mudrock' reactions; relatively open pores into which reactive fluids were focussed; the presence of detrital shell as 'seeding points'; and the presence within the sediment pile of high permeability storm beds along which decompacting fluids could escape. Similar studies show that neoformed kaolinites precipitated from essentially meteoric pore waters at temperatures in the region of 50oC during the Cretaceous. I suggest that the emergent East Shetland Platform dominated the hydrology of these sandstones at this time, providing sufficient hydrostatic head to introduce the meteoric waters into the reservoir section. Quartz overgrowths, late stage ferroan calcites, dolomites and ferroan dolomites/ankerites, illitization of kaolinites and minor 'fibrous' illite neoformation are all interpreted to have occurred during a final stage in the burial history of these sandstones based on their relative paragenesis, stable isotopic compositions and the thermometric properties of fluid inclusions contained within authigenic quartz and carbonates. Such data indicate that this latest stage of mineralization occurred at temperatures of about 90-110oC. The similarity between these temperatures and present day formation temperatures (average 99-105oC) suggests that the development of these minerals may still be continuing at the present day.
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Moon, Benjamin C. "Ichthyosaurs of the British Middle & Upper Jurassic & the evolution of ichthyosaurs." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705452.
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Kulpecz, Alexander Andrew. "Controls on facies architecture in the Middle Jurassic Ravenscar Group, Yorkshire Coast, UK." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/8289.
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Morgans, Helen Sarah. "Early to middle Jurassic stratigraphic development, vegetation and climate change in north-western Europe." Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:4b5cae3c-7562-45b9-b2a2-543b2649b24f.
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The aim of work presented in this thesis was to explore the inter-relationships of cyclic sedimentation, relative sea-level change, and palaeoclimate as inferred from plant megafossils. To this end, the investigation focused on the classic plant-bearing Middle Jurassic succession of Yorkshire. The Middle Jurassic (Aalenian-Bathonian) Ravenscar Group of the Cleveland Basin (Yorkshire) comprises a predominantly fluvio-deltaic succession intercalated between thinner, laterally persistent marine units. There is a pronounced lateral facies change across the basin, from mainly alluvial sediments in the north to more marine deposits in the south. Although variable in character, the facies composing the sequence are described by four principal environments of deposition: alluvial, estuarine, lagoonal and marine. In an attempt to achieve a more accurate stratigraphic control on the succession, sequence-stratigraphic concepts are applied to outcrop exposures and subsurface cores. The identification of 'key surfaces' in the sequence resolves a series of lithological cycles which reflect relative sea-level fluctuations. Using this approach the Aalenian-Bathonian sequence can be subdivided into two large-scale (second-order) transgressive-regressive cycles onto which six medium-scale (thirdorder) cycles of transgression and regression are superimposed. The potential for correlating these lithological cycles regionally has been assessed by comparing coeval sections from southern Scandinavia. Plant-bearing fluvio-deltaic sequences from Bornholm and Scania were chosen as a means for appraising the lateral continuity of the cycles, and assessing what factors might have controlled their development. Study of floral remains from the Ravenscar Group within the context of this stratigraphic framework yields valuable palaeoclimatic information. Growth-ring analysis of fossil wood of Late Pliensbachian to Late Bathonian age indicates a distinctly seasonal climate with low to moderate interseasonal variation in tree growth. Significant intraseasonal influences on wood production are implicit in the abundance of false rings. Consideration of these results within a stratigraphic context suggests that conditions during the Bathonian were comparatively hostile: a finding which is interpreted to be due to more frequent and extended water shortages associated with a drier climate. These palaeoclimatic inferences are substantiated by evidence obtained from the examination of the flora using Correspondence Analysis (CA). This approach verifies the presence of a temporal fluctuation in the flora found by previous investigations and, furthermore, highlights physiognomic trends in the flora with time. The results from CA also indicate adverse growing conditions during the Bathonian, emphasized by the prevalence of xeromorphic taxa.
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Gill, Caroline E. "Controls on strain localisation in the Middle to Late Jurassic North Sea rift system." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/2489.
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Extensional fault propagation and linkage play an important role in the structural and sedimentological development of rift basins. In this study, use of 85,000km² 3D seismic data provides a new and unique opportunity to evaluate and quantify the processes of fault growth within an evolving rift system. The study uses a comprehensive dataset from the East Shetland Basin and North Viking Graben, northern North Sea to document the evidence for, and effects of fault growth during the Mid to Late Jurassic (Bajocian to Ryazanian) rift episode. Integration of excellent biostratigraphic control with these seismic data enables enhanced temporal control than that which can be achieved in the field. The data allows the development of a new 4-dimensional holistic model in which strain localisation can be shown to be the dominant control on the spatial and temporal evolution of structure in an evolving rift province. The significance of my approach is the integration of seismic stratigraphic analysis combined with facies analysis and biostratigraphy in the East Shetland Basin to demonstrate that during the Mid to Late Jurassic rift episode the locus of extension migrated from west to east towards the Viking Graben. Systematic documentation of the variation in age of syn-rift deposits across the basin shows that motion on faults ended progressively throughout the Kimmeridgian and Portlandian with the latest motion occurring on the Visund-Gullfaks- Alwyn fault array during the Volgian. The effect of strain localisation towards the basin centre with time caused passive rotation of earlier (more westerly) structures (e.g. Snorre) and their hangingwall depocentres. This is the first study to challenge the traditional view that the Mid to Late Jurassic structures in the East Shetland Basin were active synchronously throughout the rift episode. Detailed interpretation of the syn-rift architecture associated with four major faults situated on a 100km long, east-west transect across the basin allows the development of a detailed model in which the timing of activity on a suite of faults can be accurately quantified. Initially, during the Upper Bajocian, extension was characterised by a large number of small faults of both dip directions which grew by radial tip propagation and subsequent segment linkage. Strain was initially focussed onto a small number of throughgoing fault arrays at the expense of less optimally positioned structures. The focussing of strain onto these structures resulted in an increased slip rate and upward bowing of the footwalls, leading to the development of release faults formed as a result of differential vertical displacements along the length of the fault. These small (less than 10km long) structures form perpendicular to the main fault and show maximum displacement of c. 300m at their proximal end decreasing away from the main fault. As the rift episode progressed, strain was gradually localised towards the rift axis. It culminated in the Ryazanian with localisation of strain onto the rift axis. At this time activity was primarily confined to a single thoroughgoing fault, the Visund-Gullfaks Fault, defining the western edge of the North Viking Graben. As such the Visund-Gullfaks Fault developed to be the largest fault in the basin both in terms of length (125km) and maximum accumulated displacement (>5km) as a result of the basinward (eastward) migration of the locus of extension.
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Maxwell, Gregor. "The sedimentology and sequence stratigraphy of the Middle Jurassic Beryl Formation, Quad 9, U.K.C.S." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=236949.
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Quad 9 of the U.K.C.S., North Sea is located 215 miles NE of Aberdeen. It contains four producing fields with over 400 mmbbls of oil and NGL's and 5.1 TCF of gas initially in place. The major reservoir unit is the Middle Jurassic (Bajocian to Bathonian) Beryl Formation, a marginal to shallow marine deposit which varies in thickness from 150' to 1100' across the studied area. It was deposited within the Beryl Embayment, a transfer zone between two actively extending basin bounding faults of the South Viking Graben, prior to the onset of the major rifting phase during the Callovian to Ryazanian. The objectives of the thesis were to provide a revised sedimentological model for the area accounting for the contrasting sedimentary styles present within the Beryl Formation and to unify the different correlation schemes used by the different operating companies in the area. It was based on well data from 58 cored and a further 79 uncored sections spreading nine licence blocks within Quad 9. Reservoir engineering, biostratigraphic and structural data has also been used for a fully integrated study. Initial core logging identified 32 facies and 10 trace fossil assemblages which were subsequently integrated into 14 facies associations. These were then extrapolated further into the uncored sections by wireline facies associations. Correlation was initially driven by comparison of cored sections but finalised by an integration of the reservoir engineering and biostratigraphic data. Outcrop work on the Middle Jurassic of Skye and Companian of eastern Utah provided an analogue study to accompany the downhole data. Quad 9 can be split up into three main areas distinguished by different stratigraphic histories, the southern area consisting of the Buckland and Sorby Fields, the central area consisting of the Beryl, Nevis, Ness and Linnhe Fields and a northern area consisting the Bruce and Keith Fields.
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Cook, Preston Scott. "Sedimentology and Stratigraphy of the Middle Jurassic Preuss Sandstonein Northern Utah and Eastern Idaho." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6206.
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The purpose of this study is to analyze the sedimentology and stratigraphy of the Middle Jurassic Preuss Sandstone and re-evaluate past sedimentological interpretations. The Preuss is located in northern Utah, western Wyoming and eastern Idaho and is stratigraphically equivalent to the Entrada Sandstone, which is Callovian in age (Dossett et al., 2014). This study is the first attempt at 1) a sequence stratigraphic framework, 2) a petroleum system analysis and 3) an extraterrestrial analog study for the Preuss. This study frames the Preuss within three broad facies groups: marine, coastal and terrestrial. The marine group includes the open marine and restricted marine facies with associated subfacies, the coastal group includes coastal sabkha and associated subfacies, and the terrestrial group includes alluvial, inland sabkha and eolian facies with associated subfacies. Three sections in northern Utah and one section in eastern Idaho compromise the focus of this study. The three Utah sections were measured and described, and samples were collected from two Utah sections and the Idaho section. The Preuss Sandstone was deposited in an asymmetrical retroarc basin, consequently the Preuss thickens from the east towards west-central Utah and the Jurassic Elko highlands. The deposits are mostly terrestrial, which is in accord with recent sedimentological interpretations, but at odds with the old paradigm, which postulates that the Entrada and Preuss were largely tidal in origin. There are marine transgressions within the trough of the retroarc basin, and the transgressions affect terrestrial sedimentary patterns. During marine incurstions, alluvium shed off the highlands is confined west of the seaway, and does not prograde east of the trough until all the available accommodation is filled. The Preuss was deposited during a complete third-order sequence-stratigraphic cycle that lies within the Lower Zuni II second-order lowstand. The Preuss Sandstone can be used as an outcrop analog for ancient and modern environments both here on Earth and on other planetary bodies. The petroliferous Norphlet Formation along the U.S. Gulf Coast was deposited in an environment very similar to the Preuss, but the Waltherian succession of facies might be slightly different. Likewise, the facies present in the Preuss are analogous to modern arid environments, such as the Persian Gulf. Furthermore, the alluvial, sabkha, eolian and shallow marine facies of the Preuss are highly similar to facies observed in ancient Martian environments and modern environments on Saturn's moon, Titan.
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Gregory, Francis John. "Middle and upper jurassic foraminifera and radiolaria of Scotland : an integrated biostratigraphical and palaeoenvironmental approach." Thesis, University of Hull, 1995. http://hydra.hull.ac.uk/resources/hull:3950.
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This study is an integrated biostratigraphical and palaeoenvironmental analysis of foraminiferal and radiolarian distribution from all the major Middle and Upper Jurassic marine deposits of Scotland. These sampled sites are divided between two basins with Staffin Bay and Bearreraig Bay within the Inner Hebrides Basin, North West Scotland; and Brora, Balintore, Helmsdale and Eathie Haven representing the Inner Moray Firth Basin, North East Scotland.A detailed taxonomic section is presented, which provides the means of comparison of microfaunal events between sites. A combined total of 212 species are described, of which 183 are foraminifera and 29 radiolaria; this includes a total of 23 species not previously recorded, comprising 16 foraminiferal and 7 radiolarian taxa.A Callovian to Lower Kimmeridgian biozonal scheme, the first detailed attempted for the onshore UK, is constructed primarily using the Staffin Bay succession as the type section. It is based upon an integration of distinct foraminiferal and radiolarian taxa and events. This microbiostratigraphy is implicitly tied to the Boreal type ammonite scheme and comprises a total of 9 biozones and 12 sub-biozones. The new biozones are then correlated and compared with the other Scottish sites as well as other world-wide schemes.A sequential palaeoenvironmental analysis is outlined, firstly by pinpointing microfaunal assemblages that are based upon a combination of the distribution of the major suborders, the species diversity and faunal abundances, as well as integrating the facies types and probable prevalent substrate conditions. These assemblages are then used to define palaeoenvironmental models for each recorded succession, and are related to prevailing substrate and sea water conditions and distance from the 'palaeoshoreline'. As the assemblages are shown to reflect particular conditions this allows a generalised basin development model to be assessed, related to sea-level changes (transgressions and regressions). All the sites are subsequently correlated palaeoenvironmentally.The relevance of facies dependant distribution is also examined, particularly for benthic foraminiferids. The main conclusion reached is that facies dependence restricts the occurrences of taxa. However, this is not a constant feature as some specific taxa show the ability to colonise several facies types. It is this factor that permits a biostratigraphy to be constructed. Overall, assemblages appear to be related directly to a particular facies, which permits palaeoenvironmental changes to be assessed.Finally the extensive Middle and Upper Jurassic literature is examined and a generalised world wide biogeography constructed. Four provinces are defined based on characteristic foraminiferal and radiolarian assemblages.
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Al-Dhubaib, A. "Taxonomy and palaeoenvironments of Middle and Late Jurassic foraminifera and its associations of Saudi Arabia." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/749888/.
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The recent studies of the high-resolution depositional cyclicity of the Saudi Jurassic carbonates have revealed the stratigraphically and biostratigraphically complexity that mainly result from relative sea-level changes. Studying the environmental sensitivity of benthic foraminifera, associated microfossils and macrofossils has provided a potentially valuable technique for determining subtle variations in the depositional environment and also provide a proxy for sea-level fluctuations. Middle and Late Jurassic carbonates of Saudi Arabia were deposited on a very extensive shallow submarine platform that extended over most of the Arabian Plate. Dhruma, Tuwaiq Mountain Limestone and Hanifa Formations are included in this study. The assigned age for the Middle Dhruma Formation is Late Bathonian to Middle Callovian age for the Upper Dhruma Formation. The Lower Tuwaiq Mountain Limestone Formation is of the Middle Callovian age and Late Callovian is assigned for the Middle and Upper Tuwaiq Mountain Limestone Formation. Early to Middle Oxfordian is dated for the Lower Hanifa Formation and Late Oxfordian-Early Kimmeridgian for the Upper Hanifa Formation. This study is based on semi-quantitative micropalaeontological analysis of closely-spaced thin sections from subsurface and outcrop localities. The subsurface samples are from four carbonates reservoirs in eastern Saudi Arabia and one stratigraphic well in central Saudi Arabia near the type area of the studied formations. The outcrop samples are from age-equivalent outcrops of these reservoirs in central Saudi Arabia, near their formations type area. Reviewing and improving the existing Middle and Upper Jurassic benthonic foraminiferal taxonomy have been achieved in this study. About sixty biozones and seven biofacies have been established for the whole studied localities. These biozones and biofacies have provided significant contributions towards understanding the stratigraphy and palaeoenvironments of the studied formations from the Middle Dhruma Formation to the uppermost Hanifa Formation in both outcrop and subsurface localities.
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Shabestari, Gholamreza Mirab. "Diagenesis and reservoir properties of the Great Oolite Formation (Middle Jurassic), Weald Basin, south of England." Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433035.
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Piper, Adrian T. "Evaluation of palynofacies analysis in the interpretation of depositional environments in the Middle Jurassic of Yorkshire." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295476.
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Ejembi, John Idoko. "SEDIMENTOLOGY AND STRATIGRAPHIC EVOLUTION OF THE PARADOX BASIN IN THE MIDDLE-LATE JURASSIC, WESTERN UNITED STATES." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1624.
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The Middle-Upper Jurassic sedimentary rocks (i.e., the Entrada Sandstone, Wanakah Formation, and Morrison Formation) in western Colorado were mostly deposited in the Paradox Basin and form part of the modern-day Colorado Plateau in the Cordilleran foreland region. These rocks were deposited in the Mesozoic during periods of active tectonic processes in western and eastern Laurentia due to the Cordilleran magmatism and continued rifting of Pangaea, respectively. The Middle-Late Jurassic sedimentary record in the Paradox Basin shows rapid transition in depositional environments, pulses in sedimentation, post-depositional alteration, and changes in provenance. This dissertation project utilizes three main scientific tools to address pertinent geologic questions regarding the stratigraphic evolution of these units in the Paradox Basin. U-Pb detrital zircon geochronology of sandstones from these units show local and distal provenance sources. The anisotropy of magnetic susceptibility (AMS) of sediments and rock magnetism attribute the post-depositional alteration to percolation of ferruginous fluids driven by an adjacent regional uplift. Multi-geochemical proxies in paleosols suggest variable redox conditions, and a sub-humid to humid paleoclimate with seasonal precipitation during sedimentary hiatus in the Paradox Basin.
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Slater, Sam. "A quantitative analysis of the dispersed spore and pollen record from the Middle Jurassic of Yorkshire, UK." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/11731/.
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Quantitative analysis of the distribution of dispersed sporomorphs (spores and pollen) has been used to assess vegetation change through the Middle Jurassic Ravenscar Group (Aalenian–Bathonian) from North Yorkshire, UK. Aalenian, Bajocian and Bathonian strata possess relatively distinct sporomorph assemblages regarding taxon occurrences, abundances and diversities (richness), suggesting a dynamic history regarding the nature of parent vegetation. Aalenian palynofloras are composed of a heterogeneous mixture of conifers, ferns, simple monosulcate pollen producers, sphenophytes and Caytoniales; Bajocian palynofloras are co-dominated by conifers and ferns; and Bathonian palynofloras are highly rich and contain assemblages of abundant ferns, conifers, lycophytes, pteridosperms/conifers and Caytoniales. Temporal variations in assemblages are a result of long-term depositional environmental changes that influence depositional taphonomic processes and parent vegetation. Comparison of the dispersed sporomorph and plant megafossil record through the Hasty Bank plant bed demonstrates that both fossil assemblages represent different aspects of the palaeoflora due to a multitude of ecological and taphonomic biases. Specifically, conifers and ferns are underrepresented in plant megafossil assemblages, bryophytes and lycopsids are represented only in sporomorph assemblages, and sphenophytes, pteridosperms, Caytoniales, Cycadales, Ginkgoales and Bennettitales are comparatively underrepresented in sporomorph assemblages. Biases between assemblages include, variation in sporomorph production levels, depositional environment and differential sporomorph and parent plant durability. Megaspore occurrences from the Middle Jurassic of Yorkshire are reviewed and a new megaspore genus, named Reticuspinosporites whytei is formally described. Transmission electron microscope analysis of the spore wall ultrastructure suggests lycopsid and possibly selaginellalean affinities.
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Jennings, George R. III. "Facies Analysis, Sequence Stratigraphy and Paleogeography of the Middle Jurassic (Callovian) Entrada Sandstone: Traps, Tectonics, and Analog." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4083.
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The late Middle Jurassic (Callovian) Entrada Sandstone has been divided into two general facies associations consisting primarily of eolian sandstones in eastern Utah and "muddy" redbeds in central Utah. Sedimentary structures within the redbed portion are explained by the interfingering of inland sabkha, alluvial, and eolian depositional systems. A complete succession from the most basinward facies to the most terrestrial facies in the Entrada Sandstone consists of inland sabkha facies overlain by either alluvial or eolian facies. Where both alluvial and eolian facies interfinger, alluvial facies overlain by eolian facies is considered a normal succession. Sequence boundaries, often identified by more basinward facies overlying more landward facies, are observed in the Entrada Sandstone and are extrapolated for the first time across much of Utah, including both the eolian-dominated and redbed-dominated areas. Using these sequence boundaries as well as recent tephrochronologic studies, three time correlative surfaces have been identified in the Entrada. Based on the facies interpretations at each surface, five paleogeographic reconstructions and five isopach maps have been created, illustrating two major intervals of erg expansion and the location of the Jurassic retroarc foreland basin's potential forebulge. Eolian (erg-margin) sandstones pinch-out into muddy redbeds creating combination traps, as evidenced by dead oil (tar) and bleached eolian sandstone bodies within the Entrada. The Entrada Sandstone is a world-class analog for similar systems, such as the Gulf of Mexico's Norphlet Sandstone, where eolian facies grade into muddy redbed facies.
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Ross, C. Elizabeth. "Palynofacies, palaeoenvironmental change and sequence stratigraphy of the Middle Jurassic, Cleveland Basin and Brent Group of the UK." Thesis, University of Oxford, 1999. https://ora.ox.ac.uk/objects/uuid:f6e7c4a2-a4e0-49bb-b897-b500d74ce371.
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Palynofacies analysis, which is the study of microscopic organic matter can, in association with sedimentological and palaeoecological data, provide temporal and spatial resolution in the characterisation of sedimentary environments and potentially, vegetation and climate. However, the reliability of palynofacies analysis as a tool for environmental reconstruction has been questioned recently. This uncertainty is due a number of factors, including the lack of standardisation in the processing and counting of organic matter, subjective and vague terminology used to classify organic matter, and existence of numerous classification schemes. These have all restricted comparison between studies and hence hampered the advance of palynofacies analysis. The most important factor is, however, limited understanding of the controls which govern the genesis of particular associations of particulate organic matter. These issues were addressed using a two-fold approach. Firstly, the particulate organic matter classification scheme created by Lewis in 1995 was tailored to produce a robust hierarchical classification scheme. Secondly, multivariate statistical analysis was applied to a Middle Jurassic data set. This revealed that the primary control upon the nature of the organic matter associations is preservation potential which is affected by redox status, and to a lesser extent by the degree and duration of transportation and disturbance to which the organic-matter has been subjected. The secondary influence was determined to be a change in the nature of organic matter through time. Following this analysis 19 different organic-matter assemblage groups were defined to decipher palaeoenvironmental changes during the Middle Jurassic. Variations in the associations of organic matter through the Aalenian to Bathonian reflect changes in the redox status, proximity to source, salinity and hydrodynamics. This investigation suggests that aridity and/or pronounced seasonality commenced during the early Bajocian of the region which is earlier than the findings of previous investigations. This is based principally on the concomitant increase in black fragments (charcoal) and acme of Classopollis pollen in both the Cleveland Basin and Brent Group. The black fragments are probably charcoal rather than post-depositionally altered fragments because they occur in a range of oxic and anoxic environments, in conjunction with brown fragments, and in a range of lithofacies. These results not only permit the characterisation of the environment of deposition but also illustrate that palynofacies yields a discernible climatic signal.
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Ketchum, Hilary Frances. "The anatomy, taxonomy and systematics of three British Middle Jurassic pliosaurs (Sauropterygia: Plesiosauria), and the phylogeny of Plesiosauria." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612160.
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Metcalf, Sara J. "The palaeoenvironment and palaeoecology of a Middle Jurassic vertebrate-bearing fen-type paleosol in a coastal carbonate regime." Thesis, University of Bristol, 1995. http://hdl.handle.net/1983/955beb87-8c25-4857-ac91-c3451390ff62.
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Wolniewicz, Andrzej. "The anatomy, taxonomy and systematics of Middle Triassic-Early Jurassic ichthyosaurs (Reptilia: Ichthyopterygia) and the phylogeny of Ichthyopterygia." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:8855adf9-0a5a-46d3-b848-1f7d9865e479.
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Ichthyosaurs were a successful group of Mesozoic marine reptiles spanning a time interval of nearly 160 million years, from the Early Triassic to the early Late Cretaceous. Although ichthyosaurs have a long history of research, dating back to the early 18<sup>th</sup> century, significant controversies still surround their anatomy, taxonomy and evolution. The revision of the cranial anatomy of the basal ichthyosaur Cymbospondylus from the Middle Triassic (Anisian) resolves a 100-year controversy surrounding the arrangement its skull bones. Comparisons with the recently discovered colossal, predatory ichthyosaur Thalattoarchon result in the identification of shared synapomorphies, which provide evidence for a close relationship between the two taxa. Together with other, recent discoveries from China, this demonstrates the rapid ecomorphological diversification of ichthyosaurs in the early Middle Triassic. The incompletely sampled Late Triassic marine fossil record hinders our understanding of ichthyosaur evolution across the Triassic-Jurassic boundary. A new genus and species of large-bodied, early parvipelvian (fish-shaped) ichthyosaur from the Late Triassic (upper Norian) of British Columbia, Canada, is described. The new taxon is characterized by the possession of labiolingually flattened, bicarinate tooth crowns. Its co-occurrence with other small- to medium-sized parvipelvians, representing different ecomorphologies, demonstrates that parvipelvian ichthyosaurs were already ecomorphologically diverse at the beginning of their evolutionary history and maintained high ecological diversity throughout the Late Triassic. The ichthyosaur diversity of the Lower Jurassic (HettangianâPliensbachian) of the United Kingdom is still poorly understood, due to the lack of detailed studies of ichthyosaur anatomy. Here, I describe a new genus and species of ichthyosaur, defined by the possession of five autapomorphies and a unique combination of both plesiomorphic and derived characters. Phylogenetic analysis recovers the new taxon as an early-diverging parvipelvian, providing evidence of a temporally staggered, rather than catastrophic, ichthyosaur turnover at the Triassic-Jurassic boundary.
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Niwa, Kohsuke, and Kazuhiro Tsukada. "Jurassic radiolarian fossils from the Miyakoda Formation in the Lake Hamana area, Shizuoka Prefecture, central Japan." Dept. of Earth and Planetary Sciences, Nagoya University, 2004. http://hdl.handle.net/2237/7638.
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Abdelhady, Ahmed [Verfasser], and Franz [Akademischer Betreuer] Fürsich. "Palaeoenvironments and palaeoecology of the Middle and Upper Jurassic succession of Gebel Maghara (Sinai) / Ahmed Abdelhady. Gutachter: Franz Fürsich." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1064996531/34.
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Kennedy, Jonathan David. "Palaeoecology, palaeoceanography, mineralogy, and stable isotopes of forminifera and ostracods from the Middle and Upper Jurassic of Great Britain." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358717.
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Richards, Philip Charles. "Lower and Middle Jurassic sedimentology of the Beryl Embayment, and implications for the evolution of the northern North Sea." Thesis, University of Strathclyde, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302823.
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Watkinson, Matthew Philip. "Triassic to Middle Jurassic sequences from the Lusitanian Basin Portugal, and their equivalents in other North Atlantic margin basins." Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330105.
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Chandler, Robert Baron. "High resolution ammonite biostratigraphy and biochronology of the Aalenian and Bajocian stages (Middle Jurassic) of Dorset and Somerset, UK." Thesis, University of Portsmouth, 2018. https://researchportal.port.ac.uk/portal/en/theses/high-resolution-ammonite-biostratigraphy-and-biochronology-of-the-aalenian-and-bajocian-stages-middle-jurassic-of-dorset-and-somerset-uk(ac6722c9-0bbc-44a5-a9d8-2f99fb46b75f).html.
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The Inferior Oolite Formation of southern England is one of the foundations and testing grounds for the biostratigraphy of the Aalenian, Bajocian and lowermost Bathonian stages of the Middle Jurassic. The successions are highly discontinuous both vertically and laterally, comprising thin, lenticular deposits initially seemingly of limited use for standard chronostratigraphy. The beds are highly fossiliferous and are the source of many nominal genera and species of the classical literature introduced by S.S. Buckman. Publications herein represent a lifetime's work and incorporate research that focuses on the re-exposure, collecting and recording of the stratigraphical succession of many historical locations. This thesis reexamines, refines and advances the understanding of the biostratigraphy of the Inferior Oolite ammonite assemblages of Dorset and Somerset and is an important resource for comparison with many areas worldwide and for which this author provides commentary. Critical assessment is made of new, large, in situ, collections of well-preserved specimens made by the author, supported by data and evaluation against types in several museums. New taxa are erected accordingly. Specimens have been prepared using state of the art methods that allow evaluation of the complete shells, stages of growth and sexual dimorphism. The precise levels from which almost all of Buckman's Inferior Oolite specimens came is now known and this has enabled the variability of the fauna at discrete levels to be assessed, and has eliminated many ambiguities in the literature, to select those names that are useful and to decide which must be abandoned. Interpretation is made of patterns of ammonite migration, provincialism and Middle Jurassic biogeography. Distinguishable biohorizon lists present the biostratigraphy of the ammonites alongside correlation charts. Presently (2017), in the British Aalenian, there are 18. In the Lower Bajocian, there are 30 and the Upper Bajocian has 11 with 3 faunal horizons identified that require further study. Only the earliest Bathonian strata are considered and 3 horizons are recognised to date. It is therefore possible to discriminate 62 biohorizons in Dorset and Somerset for strata of the Aalenian-lowest Bathonian.
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Thomson, Robert Charles. "Lower to middle Jurassic (Pliensbachian to Bajocian) stratigraphy and Pliensbachian Ammonite fauna of the northern Spatsizi area, North Central British Columbia." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25059.
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The lithostratigraphy and Pliensbachian ammonite fauna of a sequence of Pliensbachian to Bajocian sedimentary rocks, informally referred to here as the Spatsizi Group, from the Spatsizi map-area (104 H) in north-central British Columbia are examined in this thesis. Twenty Five species of ammonites representing fifteen genera from Pliensbachian rocks of the Spatsizi Group are described and their stratigraphic ranges in the thesis area determined. The Spatsizi fauna is comprised primarily of ammonites of Tethyan aspect and also contains elements endemic to the East Pacific faunal realm. The Spatsizi fauna is located on the northern half of the Stikine terrane of the western Cordilleran eugeocline, and is surrounded by biogeographically related faunas containing ammonites of Boreal affinity in addition to Tethyan and East Pacific forms, indicating that northern Stikinia occupied a position within the mixed Boreal/Tethyan zone of the eastern Pacific region during the Pliensbachian. Subsequent tectonic displacement of Stikinia transported it northward to its present position.
The Spatsizi Group is informally defined and is divided into five informal formations; the Joan, Eaglenest Gladys, Groves, and Walker Formations. Each formation reflects deposition in a different sedimentary environment affected by varying degrees of volcanic (epiclastic or pyroclastic) input Rocks of the Spatsizi Group represent the basinward sedimentary equivalents to the coeval Toodoggone volcanics that formed along the southern flank of the Stikine Arch. Facies transitions from the Stikine Arch in the north to the sedimentary basin in the south are best developed in sediments deposited during Pliensbachian and Early Toarcian times, when epiclastic sands and conglomerates accumulating on the southern flank of the arch graded southward into silts and muds in the basin.
Two phases of non-coaxial deformation folded and faulted the rocks in the thesis map area. Deformation was probably related to interaction between the Stikinia and the North American continental margin during accretion.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate
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Lewis, J. J. M. "Studies on reservoir heterogeneity and permeability anisotropy in lithified carbonate sands from the Great Oolite Formation (Middle Jurassic) of Southern England." Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380840.
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Anquetin, J. "A new stem turtle from the Middle Jurassic of the Isle of Skye, Scotland, and a reassessment of basal turtle relationships." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18899/.
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A recent phylogenetic analysis of turtle interrelationships suggests that the Middle Jurassic was a crucial time period for understanding the evolution of crown-group turtles. However, turtle material of this age is scarce worldwide. Here, a new stem turtle, Eileanchelys waldmani, from the Middle Jurassic (Bathonian) of the Isle of Skye, Scotland, is described and compared to other basal species. With cranial and postcranial remains of several individuals, this is the most comprehensive Middle Jurassic turtle material known to date. Eileanchelys waldmani documents an intermediate stage in the evolution of early turtles between the Early Jurassic Kayentachelys aprix and the crown-group. Whereas most stem turtles are interpreted as terrestrial forms, taphonomic evidence suggests that E. waldmani may have been aquatic (freshwater), indicating that basal turtles were ecologically more diverse than previously thought. This new material provides the basis for a reassessment of other Middle Jurassic turtle remains from the UK, especially revisions of material from Kirtlington and Stonesfield (Oxfordshire). The material from Kirtlington is attributed to Paracryptodira and represents the earliest occurrence of this group. The name 'Protochelys blakii', which had been proposed for the Stonesfield remains, is considered to be a nomen dubium as this material lacks diagnostic features. However, this material is remarkable as it consists of fossilised epidermal scales from the carapace. A new phylogeny is proposed, resulting from a cladistic analysis of a revised and updated version of a previously published data set. Nineteen new species are included in order to achieve a more thorough representation of basal turtle taxa. Heckerochelys romani and Condorchelys antiqua are found to be more basal than Eileanchelys waldmani. Chengyuchelyids (Middle Jurassic of China) may be stem turtles more basal than Kallokibotion bajazidi. Naomichelys speciosa is closely related to meiolaniids and Mongolochelys efremovi, while Siamochelys peninsularis is nested within xinjiangchelyids.
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Hogg, Nicholas Mark. "A palynological investigation of the Scalby Formation (Ravenscar Group, Middle Jurassic) and adjacent strata from the Cleveland Basin, north east Yorkshire." Thesis, University of Sheffield, 1993. http://etheses.whiterose.ac.uk/14604/.
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Hunter, Aaron William. "Model for the palaeoecology of echinoderms from the middle Jurassic (Bathonian) marginal marine facies of Great Britain, France and the United States." Thesis, Birkbeck (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439306.
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Holwerda, Femke Marleen [Verfasser], and Oliver [Akademischer Betreuer] Rauhut. "Revision of basal sauropods from the Middle Jurassic of Patagonia and the early evolution of sauropods / Femke Marleen Holwerda ; Betreuer: Oliver Rauhut." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1204365504/34.
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Grainger, Nancy. "Petrogenesis of Middle Jurassic to Miocene magmatism within the Nechako plateau, central British Columbia, insight from petrography, geochemistry, geochronology and tracer isotope studies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0014/MQ60123.pdf.
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Hudson, Neville. "The middle Jurassic of New Zealand : a study of the lithostratigraphy and biostratigraphy of the Ururoan, Temaikan and Lower Heterian Stages (?Pliensbachian to ?Kimmeridgian)." Thesis, University of Auckland, 2000. http://hdl.handle.net/2292/2135.
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The lithologic and biostratigraphic successions of Ururoan, Temaikan and Lower - Middle Heterian (?Sinemurian, Pliensbachian - ?Kimmeridgian) strata from southwest Auckland, south Otago and Southland, New Zealand, are described and discussed. A more logical correlation of the lithologic sequence at Port Waikato with that at Te Akau is proposed. Two new formations are introduced for the sequences on the western limb of the Kawhia Regional Syncline, the Whakapatiki Mudstone for the fine grained lower Kirikiri Group strata in the Awakino Valley and the Gribbon Formation for the Rengarenga Group strata between Marokopa and Mahoenui. In Southland a new formation (Ben Bolt Formation) is proposed for the c.1340m sequence overlying the Flag Hill Sandstone, in turn overlain by a 485m thick, mudstone-dominated formation for which a long disused name is resurrected (Lora Formation). The Lora Formation is in turn overlain by a coarse-grained unit, for which the name West Peak Formation is proposed. In the absence of suitable alternatives, a subdivision of the Ururoan Stage into a Lower Ururoan, the range-zone of pseudaucella marshalli, and an Upper Ururoan, the interval-zone between the last appearance of Pseudaucella marshalli and the first appearance of a Temaikan fauna is proposed. The existing three-fold subdivision of the Temaikan Stage is emended. Belemnopsis mackayi and B. deborahae are retained as the indices of the Temaikan and its lowest subdivision, as they are present in most sections at a consistent stratigraphic position. Retroceramus (Fractoceramus) inconditus is proposed as the basal Middle Temaikan index species. Retroceramus(R.) brownei, which first appears consistently higher than R. inconditus, but below R. marwicki is proposed as the index for the upper Middle Temaikan. Retroceramus (R.) marwicki is proposed as a replacement upper Temaikan index for "Macrocephalites cf. beta-gamma" which is unsuitable. Meleagrinella n. sp. is inconsistent in its first appearance and therefore unsuitable as a Middle Temaikan index and, although confined to this stage, it ranges from Early to early Upper Temaikan. Basal Temaikan Belemnopsis spp. are absent from sections in the Catlins district whereas the earliest Temaikan taxon appearing above typical Ururoan faunas is Meleagrinella n. sp. In the absence of a better alternative Meleagrinella n. sp. is used to mark the base of the stage in the Catlins sections. However, the base of the Temaikan is here likely to be slightly younger than in other sections. Within the redefined Upper Temaikan four subdivisions based on the sequence of Retroceramus species are recognised. The lowest of these is characterised by the first appearance of R. (R.) marwicki, the second by the first appearance of R. (R.) n. sp. A., the third characterised by the first appearance of R. (R.) stehni, and the highest marked by the first appearance of either R. (R ) sp. C. (a wide triangular form) or sp. D. (an ovate flat form). The presence of these two morphologic forms indicate finer zonation of the Upper Temaikan may be possible, with further field work. The Ururoan to Middle Heterian succession of New Zealand is correlated with the international chronostratigraphic scheme based mainly on comparison of New Zealand's Retroceramus succession with that of South America and Indonesia and on relatively rare ammonites. The Ururoan is equivalent to the ?Sinemurian to Late Toarcian, Temaikan to the ?latest Toarcian to Early Callovian and the Early Heterian to the Middle Callovian to latest Middle to Late Oxfordian. Early Ururoan is correlated with the ?Sinemurian to Pliensbachian based on the presence of the ammonite Juraphyllites. Presence of the Early Toarican ammonites Harpoceras cf. falcifer and Dactylioceras spp. in the Late Ururoan indicates a potential international correlation of ?Late Pliensbachian to Late Toarcian. A ?late Toarcian to Aalenian correlation for the Early Temaikan is suggested by the presence of the European belemnite Brevibelus zieteni. Retroceramus (Fractoceramus) inconditus is similar to the Northern hemisphere Mytiloceramus lucifer and the northern hemisphere Retroceramus gr. popovi and thus suggests a latest Aalenian to Early Bajocian correlation of the Middle Temaikan. The earliest Late Middle Temaikan Retroceramus (Retroceramus) marwicki is also present in the Late Bajocian (Rotundum Zone) of Argentina. ?Teloceras gr. banksi, ?stephanoceras (S.) gr. humphriesianum, Chondroceras (C.) gr. evolvescens, C. (C.) cf. recticostatum, and C. (Defonticeras) cf. oblatum are present in the Middle Temaikan reinforcing an earliest to late Early Bajocian correlation for this substage. Toxamblyites aff. densicostatus Sturani, Chondroceras (C.) gr. Evolvescens (Waagen), C. (Schmidtoceras) orbignyanum (Wright), C. (Defonticeras?) sp. indet. occur with Retroceramus marwicki indicating an Early to Late Bajocian correlation for this zone, slightly broader than in Argentina. However, somewhat anomalously the first of these ammonites suggests a Mid Aalenian to Early Bajocian correlation. The succeeding zone (Retroceramus (R.) n. sp A. zone) has yielded the Latest Bathonian Xenocephalites grantmackiei and Lilloettia aff. boesei. Retroceramus(R.)stehni is the index for the third Upper Temaikan Retroceramus zone and is also known from the latest Bathonian to Early Callovian of Argentina. In New Zealand R. stehni is associated with Lilloettia cf. Lilloetensis and Xenocephalites cf. stipanicici which also indicate a latest Bathonian to Early Callovian correlation. The fourth and highest zone of the Upper Temaikan has yielded the ammonites Araucanites marwicki, Eurycephalites gr. extremus, Iniskinites gr. cepoides and Choffatia (Homoeoplanulites) sp. suggesting an Early to Middle Callovian correlation. The overseas relationships of the associated Retroceramus (R.) spp. C. and D. are unknown. The Heterian index Retroceramus (Retroceramus) galoi is of Oxfordian age in Indonesia where it is associated with Malayomaorica malayomaorica. In New Zealand Araucanites marwicki and Sulaites heteriense are present in the Early Heterian, below the incoming of Malayomaorica malayomaorica, low in the range of Retroceramus galoi. The presence of Sulaites high in the Early Heterian suggests a ?Middle to Late Oxfordian correlation while Araucanites indicates the lowest part of the range of Retroceramus galoi could be slightly older, perhaps Upper Callovian. The biostratigraphic scheme presented here is a significant advance on those proposed previously.
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Gilbert, Clark. "Depositional patterns and stratal relationships on the distal margins of a foreland basin: Middle Jurassic Gypsum Spring and lower Sundance Formations, Bighorn Basin, WY." Thesis, Wichita State University, 2012. http://hdl.handle.net/10057/5595.
Full textAbstract:
Depositional patterns and stratal relationships in the Middle Jurassic Gypsum Spring and lower Sundance Formations were influenced by a combination of paleotopographic highs and eustatic changes in the eastern Bighorn Basin. Most of these highs are of tectonic origin related to an island arc collision to the west and assumed to be reactivations of crustal weaknesses from earlier western North American orogenies. Although overall basin geometry was affected by the encroaching tectonic load, the study area is far enough away from the orogenic front that it behaves like a passive margin in a ramp setting in response to relative sea level changes. The Middle Jurassic section in the Bighorn Basin records three major transgressive regressive cycles. Many of these contain high-order cycles identifiable by evidence of subaerial exposure in outcrop or by a geophysical log signature showing cyclic alternating peaks and troughs within a given lithologic unit. Chert pebble lag deposits have been used by previous workers to locate regional unconformities in the Bighorn Basin and throughout the Western Cordillera. One of these unconformities, the J-2 surface, is particularly enigmatic. If these lag deposits do in fact mark the J-2 unconformity the surface in the Bighorn Basin is localized and only present in the vicinity of paleotopographic highs, the Black Mountain High being the most prominent. The chert pebbles were shed off of this high and deposited locally and sporadically across two lithofacies units. The combination of paleotopography, tectonics and eustatic changes all contributed to the stratigraphy of the Middle Jurassic section. A sequence stratigraphic model was developed to gain insight into the timing of these tectonic and eustatic events in relation to deposition.<br>Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Geology
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Ferreira, Jorge. "Palaeoenvironmental and palaeoceanographic changes during the Lower to Middle Jurassic ( Toarcian-Aalenian, ~183-171 Ma) : new evidences from calcareous nannofossils of the Lusitanian Basin." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1033/document.
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Le biome marin du Toarcien inférieur a subi une des crises les plus significatives de l'histoire de la Terre, qui a affecté les mers épicontinentales du globe. Ces bassins épicontinentaux sont également caractérisés par l'accumulation de grandes quantités de matière organique dans les sédiments de l'époque, ce qui a été interprété comme le résultat d'un Evénement Anoxique au Toarcien inférieur (T-OAE, ~183 Ma). Le nannoplancton calcaire, qui fait partie des organismes le plus sensibles aux conditions environnementales des eaux océaniques de surface, a été profondément affecté par cette crise et sa récupération se mit en place seulement à la fin du Toarcien inférieur. Si le T-OAE a été étudié en grand détail ces dernières années, la période de récupération est beaucoup moins bien connue. A ce stade, nous ne savons pas, notamment, si la récupération de la production carbonatée primaire est représentée par un épisode rapide ou par une suite d'événements (qui feraient partie d'un plus long processus) intervenus sur quelques millions d'années après le T-OAE. Pendant les perturbations environnementales qui ont eu lieu au Toarcien inférieur, des fluctuations importantes du niveau marin ont été interprétées ainsi que des variations de la température des eaux océaniques. Après le T-OAE, le niveau marin et les températures montrent des changements plus graduels pendant une grande partie du Toarcien supérieur-Aalénien inférieur et les niches écologiques occupées par le nannoplancton calcaire sont ré-établies. Ces conditions de relative stabilité sur le long terme (~10 Ma) sont idéales pour étudier les dynamiques de la communauté des nannofossiles calcaires et, notamment, comment les différents taxons réorganisent leurs relations synécologiques. Le Toarcien-Aalénien est une période clé dans l'évolution du nannoplancton calcaire, avec des nouveaux genres qui apparaissent. Les nannofossiles de cet intervalle restent relativement peu étudié dans le Bassin Lusitanien, malgré l'importance de cette région d'un point de vue paléocéanographique. En effet ce bassin, qui était à l'origine un rift avorté lié à l'ouverture de l'Atlantique, a permis les connections entre des masses d'eaux de provenance NW européenne et sud-téthysienne. C'est dans cette région que nous retrouvons donc des mélanges de taxons liés à des différentes provinces géographiques<br>At ~183 Ma when large amounts of organic matter was dumped onto the ocean beds (known as the Toarcian Oceanic Anoxic Event, T-OAE), the Early Toarcian marine biota experienced one of the most important biological crises in Earth history. Calcareous nannoplankton was deeply affected and started only to recover from the end of the Early Toarcian. After the T-OAE, as phytoplankton communities dwelling the oceans photic layer recover from the previous disturbing conditions, the ecological niches once occupied by calcareous nannoplankton are again replenished. Located in the westernmost part of the Tethyan ocean, the Lusitanian Basin acted as a seaway between the NW Tethys and the Mediterranean Tethys provinces, therefore been actively influenced by these two different water masses. Hence such a region stands as the perfect spot to study the calcareous nannoplankton community, as its fossil remains bears species typical of both provinces. In order to appraise the nannoplankton demise and subsequent recovery, absolute and relative abundances of nannofossils were determined from pelagic marl-limestone couplets from three sections of the Lusitanian Basin. Also brachiopods shells were investigated for stable carbon and oxygen isotopes analysis. In order to independently assess the morphologic evolution of Lotharingius coccoliths, a Toarcian section from south France was studied. Different statistic methodologies were used throughout this work, in order to screen for robust and significant information from the numerous datasets that were built<br>Há cerca de 183 milhões de anos atrás, a biota marinha sofreu uma das mais importantes crises biológicas na história do planeta, quando grandes quantidades de matéria orgânica foram depositadas nos fundos oceânicos. Este episódio que teve lugar durante o Toarciano, resultou de um Evento Anóxico Oceânico (T-OAE), e afectou os mares epicontinentais à escala global. O nanoplâncton calcário, um grupo de organismos extremamente sensível às variações nas condições ambientais que têm lugar na camada superficial das massas de água, foi profundamente afectado. Foi somente no final do Toarciano Inferior que a sua recuperação se iniciou. Apesar de já muito se ter escrito sobre o T-OAE, a previsível recuperação deste grupo nunca foi sistemática nem detalhadamente estudada. Até hoje, não se sabia ainda se esta recuperação teria sido relativamente rápida, ou resultado de um processo lento e gradual que teria durado milhões de anos. Durante o Toarciano Inferior, quando as condições ambientais eram extremamente instáveis, ocorreram importantes e drásticas oscilações na temperatura e no nível médio dos oceanos. Após o T-OAE e durante todo o Toarciano e Aaleniano Inferior, as oscilações do nível médio dos oceanos e de temperatura são bastante mais suaves. À medida que a comunidade fitoplanctónica instalada na zona fótica recupera das condições extremas anteriores, os nichos ecológicos antes ocupados por nanoplâncton calcário, começam novamente a ser preenchidos. Apesar das prolongadas e suaves variações abióticas, é num ambiente então mais estável, que melhor se pode observar a evolução deste grupo, e de que forma as suas relações sinecológicas se alteraram ao longo de aproximadamente 10 milhões de anos. Apesar de ser considerado como um período onde a comunidade nanoplanctónica sofreu importantes alterações, nada se sabe em concreto que alterações foram essas que tiveram lugar após o TOAE num local tão estratégico como a Bacia Lusitânica. Situada na extremidade Oeste do Tétis e fazendo parte de um rift originado pela abertura do Atlântico, a Bacia Lusitânica actuou como um corredor que ligava livremente as massas de água das províncias mediterrânica e NW do Tétis, sendo por estas, activamente influenciada. Por essa razão, tal situação geográfica constitui um local excepcional para se estudar a comunidade de nanoplâncton calcário, uma vez que o seu registo fóssil compreende espécies típicas destas duas províncias do Tétis
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Chaumeil, Rodriguez Micaela. "Calcareous nannofossils from Los Molles Formation, south of Huincul High, Neuquén Basin, Argentina : biostratigraphy and paleobiogeographic reconstructions for the Early to Middle Jurassic (Pliensbachian-Aalenian)." Electronic Thesis or Diss., Lyon 1, 2023. http://www.theses.fr/2023LYO10116.
Full textAbstract:
Les nannofossiles calcaires représentent un groupe diversifié de fossiles, remontant au Trias supérieur et s'étendant jusqu'à nos jours, caractérisés par leur composition calcaire et une taille inférieure à 30 µm. Parmi eux, les coccolithophoridés, qui constituent la fraction la plus importante du nannoplancton calcaire, c'est-à-dire des algues unicellulaires flagellées typiquement marins appartenant à la sous-classe Calcihaptophycidae, recouvertes de plaques de carbonate de calcium (coccolithes). Les représentants fossiles des coccolithophoridés correspond à leurs restes d'exosquelette, généralement conservés sous une forme désagrégée, comme des coccolithes individuels. Leur présence dans les océans est essentielle, car ils constituent l'un des principaux groupes de producteurs primaires marins. Les données géologiques suggèrent que les coccolithophoridés ont maintenu leurs exigences écologiques presque inchangées au fil du temps, et ainsi nous permettant de reconstruire de manière fiable les conditions paléoenvironnementales, paléobiogéographiques et paléoclimatiques. L'objectif général de cette thèse est d'étudier les associations de nannofossiles calcaires des sédiments marins du Jurassique inférieur-moyen au sud haut structural de Huincul du bassin de Neuquén (Argentine) et de combiner ces informations avec celles déjà disponibles afin d'élargir et d'améliorer les ressources biostratigraphiques du bassin. En comparant ces enregistrements avec des associations de nannofossiles calcaires provenant d'autres endroits du monde, nous visons à établir des corrélations d'âge globales et à évaluer les relations paléobiogéographiques, afin de générer un modèle biostratigraphique local. L'étude se concentre sur des échantillons provenant de trois sections d'affleurement et de deux forages d'exploration. Un total de 102 échantillons de surface et 111 échantillons de subsurface ont été étudiés. En outre, des analyses géochimiques (i.e. les isotopes stables du carbone, la matière organique totale et la composition élémentaire) ont été effectuées sur 384 échantillons d'affleurement. Des techniques de décantation aléatoire et de décantation par gravité ont été utilisées pour traiter les échantillons de nannofossiles. Le degré de similitude entre les associations de nannofossiles a été évalué en effectuant une analyse NMDS et une analyse UPGMA, en utilisant l'indice de similitude de Dice. La pyrolyse et la spectrométrie de masse du rapport isotopique ont été utilisées pour traiter les échantillons en vue de l'analyse de la matière organique totale et des isotopes stables, respectivement. Pour l'analyse élémentaire, la technique de diffraction des rayons X a été utilisée. Quarante-neuf espèces sont ici décrites, répartis dans neuf famillies et une espèce insertae sedis, dont cinq sont reconnues pour la première fois pour le bassin et le Pacifique sud-est. Six biozones et de nombreuses sous-zones sont reconnues en surface et subsurface, et sont en corrélation avec les schémas biostratigraphiques de la région de la Téthys. Elles correspondent au Pliensbachien à l'Aalénien moyen - Bajocien inférieur (NJT4–NJT9). Trois intervalles d'excursions isotopiques négatives accompagnées d'augmentations de la teneur en matière organique sont identifiés. Le premier d'entre eux est considéré comme l'équivalent temporel de le T-OAE. Les autres excursions de grande amplitude enregistrées au Toarcien moyen et dans l'intervalle Toarcien-Aalénien représentent le premier enregistrement de ce type pour l'intervalle Toarcien-Aalénien dans le bassin de Neuquén, et le deuxième enregistrement pour l'hémisphère sud. Les associations de nannofossiles calcaires du Pliensbachien sont liées à celles de la région de Téthys. Le Corridor hispanique est identifié comme la voie de dispersion des nannofossiles calcaires entre les océans Paléo-Pacifique et Téthys au cours du Jurassique inférieur, ce qui indique que son ouverture remonte au moins au début du Pliensbachien<br>Calcareous nannofossils represent a diverse group of fossils, dating back to the Late Triassic and extending their record to the present day, characterised by their calcareous composition and a size under 30 microns. Among them oustand the coccolithophorids, which constitute the most important fraction of calcareous nannoplankton, i.e. flagellated unicellular algae belonging to the Subclass Calcihaptophycidae, covered by calcium carbonate plates (coccoliths), and typically marine inhabitants of the photic zone. The representation of coccolithophorids in the fossil record corresponds to their exoskeletal remnants, commonly preserved in a disaggregated form, as individual coccoliths. Their presence in the oceans is key as they are one of the main groups of marine primary producers. Evidence from the geological record suggests that coccolithophorids have maintained their ecological requirements almost invariant over time, making them key to reconstruct palaeoenvironmental, palaeobiogeographical and palaeoclimatic conditions. The aim of this thesis is to study the calcareous nannofossil associations of Early-Middle Jurassic marine sediments, south of the Huincul High, Neuquén Basin (Argentina). By combining this information with that already available, we seek to expand and improve the biostratigraphic resources of the basin, determine similarities with assemblages from other regions of the world, and evaluate the response of these organisms to important palaeoenvironmental events. The study focuses on samples from three outcrop sections —named El Matuasto I, II and III— and two exploratory boreholes —YPF.Nq.BCE.x-1 and YPF.Nq.PTU.x-2—. A total of 102 surface samples, 20 core samples and 91 drill cuttings samples were studied. In addition, geochemical analyses (i.e., stable carbon isotopes, total organic matter and elemental composition) were performed on 384 outcrop samples. Random settling and gravity settling techniques were used to process the calcareous nannofossil samples. Quantitative analysis of nannofossils required counting at least 300 individuals; in case of a sample with low abundance, counting stopped at 450 fields of view. The degree of similarity between nannofossil associations was assessed by running NMDS and UPGMA analyses, both using the Dice index. Pyrolysis and isotope ratio mass spectrometry were used to process samples for total organic matter and stable isotope analysis, respectively. For the elemental analysis, the X-ray diffraction technique was executed. In all cases, samples containing shell remains and/or evidence of weathering were avoided. Forty-nine species are described, distributed in nine families and one species insertae sedis, of which five are recognised for the first time for the basin and the southeast Pacific area, and most of them are illustrated. Six biozones and numerous subzones are recognized on the surface and subsurface sections and correlate with biostratigraphic schemes of the Tethys region. These correspond to the Pliensbachian (Biozone NJT4) to the middle Aalenian - early Bajocian (Biozone NJT9). Three intervals of negative isotopic excursions accompanied by increases in organic matter content are identified. Applying the biostratigraphic framework, the first of these is considered to be the time-equivalent of the Toarcian Oceanic Anoxic Event (T-OAE). The other high-amplitude isotope excursions recorded in the middle Toarcian and in the Toarcian-Aalenian interval represent the first record of their kind for the Toarcian - Aalenian interval in the Neuquén Basin, and the second record for the southern hemisphere. The Pliensbachian calcareous nannofossil associations recognized in one of the sections are biogeographically related to those of the Tethys region. The Hispanic Corridor is identified as the pathway of calcareous nannofossil dispersal between the Pacific and Tethys oceans during the Early Jurassic, indicating its time of opening at least from the early Pliensbachian
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Huang, Xu-Dong. "Middle-Late Jurassic Cu-Pb-Zn-bearing and W-bearing granitoids and their skarn mineralization in the Nanling Range, South China : the Tongshanling and Weijia deposits." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2038/document.
Full textAbstract:
Les granitoïdes associés aux skarn à Cu-Pb-Zn et au W, dérivent, respectivement, de la fusion partiellede roches mafiques à amphiboles dans la croute inférieure et de roches métas-édimentaires riches enmuscovite dans la croute moyenne-supérieure. Ces sources fertiles mobilisées pour la formation de cesplutons a permis la formation de gisements à Cu-Pb-Zn, et W au cours du Jurassique moyen. L’originedans la croûte moyenne de la granodiorite de Tongshanling, associée aux minéralisations à Cu-Pb-Zn, aété montrée par l’étude des enclaves microgranulaires dioritiques qui sont des restites remaniées issuesde la fusion partielle des amphibolites de la croûte inférieure. Le Cu et le Zn associées à ces plutons sontprobablement issus de la croûte inférieure et ces métaux ont probablement étés remobilisés au cours dela fusion partielle. Le Pb issue de la croute supérieur a été collecté lors de l’ascension du magma qui adonné la granodiorite. Lors de leur mise en place ces granitoïdes ont exprimé leur potentielminéralisateur. L’étude structural montre que la géométrie des corps minéralisés et en lien avec ladéformation induite par la mise en place des plutons. Les différentes expressions de la minéralisationdans le district à Cu-Mo-Pb-Zn-Ag de Tongshanling sont génétiquement lié à l’hydrothermalisme et à sonévolution lors du développement du skarn. Le granite de Weijia a cristallisé à partir d’un magma saturéen eau et riche en Fluor. Les facteurs qui ont contrôlé la formation de ce skarn magnésien riche en W,suppose l’existence d’une source enrichie en W dans les sources métasédimentaires et d’un magmariche en Fluor très différentia par cristallisation fractionnée<br>The Middle-Late Jurassic Cu-Pb-Zn-bearing and W-bearing granitoids in the Nanling Range were mainlyderived from non-simultaneous partial melting of the mafic amphibolitic rocks in the lower crust and themuscovite-rich metasedimentary rocks in the upper-middle crust, respectively. The fertile sources in theNanling Range are beneficial to the formation of Cu-Pb-Zn and W deposits during Middle-Late Jurassic.The lower-crust origin of the Cu-Pb-Zn-bearing granodiorites is further demonstrated by the dioriticmicrogranular enclaves in the Tongshanling granodiorite which are reworked restite enclaves derivedfrom partial melting of the mafic amphibolitic source. The Cu and Zn associated with these intrusionswere most probably released from the mafic amphibolitic lower crust by partial melting, whereas, Pb wasextracted from the upper crust by ascending granodioritic magmas. The emplacement of these orebearinggranitoid magmas may have a structural connection with the subsequent polymetallicmineralization in some way. For instance, the exoskarn and sulfide-quartz veins in the Tongshanling Cu-Pb-Zn deposit are evidently controlled by magma emplacement-induced wall-rock deformation. Thedifferent mineralization types and ore deposits in the Tongshanling Cu-Mo-Pb-Zn-Ag ore district aregenetically linked together in the same skarn system as the productions of evolution and zonation. TheWeijia granite was crystallized from a F-rich and water-saturated magma. The key factors controlling theoccurrence of unusual magnesian skarn W mineralization during Late Jurassic in the Nanling Rangemainly include a W enriched metasedimentary source, a fluorine-rich magma, a strong crystalfractionation, and a fluorine-rich hydrosaline melt
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Gowland, Stuart. "Facies analysis of three members of the Scarborough Formation (Middle Jurassic : Lower Bajocian) in the Cleveland Basin, northeast England : Blea Wyke, Byland Limestone and Crinoid grit members." Thesis, University of Hull, 1987. http://hydra.hull.ac.uk/resources/hull:3919.
Full textAbstract:
The Scarborough Formation is the youngest marine horizon of formation status within the dominantly deltaic Aalenian - Bajocian Ravenscar Group, Cleveland Basin, northeast England. Sedimentary facies analysis has been performed on the three conformable lithostratigraphic units which make up the bulk of the Scarborough Formation outcrop: Blea Wyke, Byland Limestone and Crinoid Grit Members. This form of analysis was performed in an effort to determine the depositional environments of the members. The information derived from the study enables one to trace the palaeogeographic evolution of the Cleveland Basin throughout much of Scarborough Formation times.The clastic Blea Wyke Member [6 facies] is attributed to deposition in a shallow [<4m], essentially microtidal,delta-destructive marine embayment. This embayment formed through non-eustatic marine transgression initiated by the compactional subsidence of an abandoned [Gristhorpe Member] delta lobe. Open to the east, the embayment covered some 2000km2 of the Cleveland Basin when fully established. A range of sand bodies evolved on the silty embayment floor in response to spatial and temporal changes in the wind-forced wave and current regime. These sand bodies included subtidal shoals, laterally extensive storm-emplaced sand blankets, and a classic delta-destructive sheet sand formed through the landward translation of a low-profile barrier bar.Under sustained rate-of-subsidence controlled marine transgression, clastic input to the Blea Wyke Member embayment eventually waned. In response, the overlying Byland Limestone Member [6 facies] was deposited in the western part of the Cleveland Basin in the form of a carbonate-dominated lagoon-barrier-inner shelf complex. The barrier component of the complex evolved through transgressive upward-shoaling under the influence of wind-forced wave and current activity. Composed of pellet lime grainstones, it protected a lagoon within which the dominant deposits were pellet lime mudstones, wackestones and packstones. Lithological and faunal similarities between the lagoon and inner shelf suggest that much of the shelf region may have comprised former back-barrier lagoon-fills exhumed during transgression.Byland Limestone Member times were terminated by an acceleration in the rate of marine transgression followed by tectonic uplift and subsequent geomorphic decay of the major landmass to the north [Mid North Sea High]. Transgression generated an east-west orientated epeiric seaway connecting the Sole Pit Trough with an areally restricted Pennine Massif. Within this seaway, clastic sediment derived chiefly from the Mid North Sea High was deposited in the form of a progradational, regional-scale composite sheet sand body: the Crinoid Grit Member [8 facies]. Deposition occurred under the combined influence of tidal currents, wind-forced currents and wave activity. Three main facies belts are recognised: paralic tidal sandwave complex, storm-dominated inner shelf and sandy middle shelf. The presence of a tidal sandwave complex is particularly interesting; it indicates that the forging of a marine connection to the west of the Cleveland Basin was necessary before tidal cyclicity could become prominent within the basin.
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Mannie, Aruna. "The rise and fall of diapirs during regional extension and its influence on the deposition of a net-transgressive coastal-plain-to-shallow-marine succession, Middle-to-Upper Jurassic, Norwegian Central Graben." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/32160.
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Regional extension in salt basins can initiate and drive salt tectonics, which may influence sediment routing systems and reservoir distribution. Structural controls on the deposition of Middle-to-Upper Jurassic, net-transgressive, shallow-marine strata preserved on the eastern flank of the North Sea Central Graben have been studied using an integrated subsurface dataset (3D and 2D seismic reflection, wireline-log, core and biostratigraphic data) in order to: (i) characterise the main structural styles in a salt-influenced rift basin; (ii) describe the sedimentology and stratigraphic architecture of the Middle-to-Upper Jurassic succession; and (iii) investigate the role that rift-related salt tectonics had on the thickness and facies distribution of the Middle-to-Upper Jurassic, syn-rift succession. Early Triassic rifting initiated reactive diapir rise of Late Permian salt, which influenced the geometry of Triassic rafts between salt walls. Middle-to-Late Triassic differential loading and density-driven subsidence resulted in further passive diapir growth, until a depletion of salt supply led to the formation of salt welds below Triassic rafts and burial of salt diapirs. A second phase of extension in the Middle-to-Late Jurassic resulted in either diapir collapse, providing accommodation for diachronous deposition of shallow-marine reservoirs, or reactive diapir rise, which influenced the depositional thickness of these reservoirs along salt wall flanks. Sedimentological core analysis of the Middle-to-Upper Jurassic in combination with biostratigraphic and wireline-log data has identified offshore, offshore transition, lower shoreface, upper shoreface and coastal-plain deposits. These deposits are arranged into upward-shallowing parasequences bounded by flooding surfaces. The timing of transgression is diachronous, with flooding and shoreline retreat controlled by the underlying rift topography. The resulting facies architecture reflects the balance between fault- and halokinesis-driven accommodation creation, and intra- and extra-basinal sediment supply. This thesis highlights the key role that salt has in modifying the tectono-stratigraphic evolution of rift basins.
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Suchéras-Marx, Baptiste. "Émergence de la production carbonatée pélagique au Jurassique moyen (180-160 Ma) : la conquête des océans par les coccolithophoridés du genre Watznaueria." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10024.
Full textAbstract:
Les coccolithophoridés sont des algues marines photosynthétiques et planctoniques qui produisent des plaques micrométriques de carbonate de calcium (CaCO3) appelés coccolithes. Ces algues sont apparues il y 210 Ma et produisent actuellement la majeure partie du CaCO3 dans les océans modernes, jouant ainsi un rôle majeur dans le cycle du carbone. Cependant, l’émergence de la production de CaCO3 océanique par les coccolithophoridés au cours du Jurassique, ainsi que son impact sur le cycle du carbone, restent très mal compris. Cette étude s’est donc focalisée sur une période du Jurassique Moyen (Bajocien inférieur, -170 Ma) enregistrant la diversification de Watznaueria, un genre de coccolithophoridé qui a ensuite dominé la production de CaCO3 océanique pendant plus de 80 Ma. L’analyse des assemblages de coccolithes du Jurassique Moyen du Portugal et du sud de la France, réalisée à l’aide d’une méthode de reconnaissance automatique appliquée pour la première fois aux coccolithes du Jurassique, a permis de quantifier l’importance de cette période de diversification sur la production de CaCO3 pélagique. En outre, la durée de cet intervalle clé a été réévaluée grâce à l’analyse cyclostratigraphique des séries sédimentaires du Sud de la France. Les variations de production de CaCO3 pélagique ainsi reconstituées ont été comparées aux perturbations du cycle du carbone enregistrées par les rapports des isotopes du carbone, et indiquent un lien probable avec une augmentation marquée de la fertilité des océans. Par ailleurs, l’analyse paléontologique montre que cette diversification correspond à l’apparition successive de différentes espèces vraisemblablement opportunistes du genre Watznaueria. Enfin, les flux obtenus de CaCO3 pélagiques, largement inférieurs à ceux observés dans les océans actuels, semblent insuffisants pour avoir eu une influence significative sur le cycle global du carbone du Jurassique Moyen<br>Coccolithophorids are photosynthetic and planktonic marine algae that produce micrometric calcium carbonate (CaCO3) platelets called coccoliths. These algae appeared about 210 Ma ago and produce today most of the CaCO3 in the modern oceans, hence playing a major role in the carbon cycle. Nevertheless, the onset of oceanic CaCO3 production by these organisms during the Jurassic and its impact on carbon cycling remain poorly understood. This study therefore focused on the Middle Jurassic interval (Early Bajocian, -170 Ma) which records the diversification of Watznaueria, an evolutionary important coccolith genus that subsequently dominated oceanic CaCO3 production for more than 80 Myr. The analysis of coccolith assemblages from the Middle Jurassic of southern France and Portugal, based on an automaticcoccolith recognition device used for the first time on Jurassic coccoliths, allowed quantifying the impact of this diversification on CaCO3 production. In addition, the duration of this key interval has been revaluated by the cyclostratigraphic analysis of sedimentary strata from southern France. The reconstructed changes in CaCO3 production were compared to carbon cycle perturbations recorded by carbon isotope ratios and indicate a probable link with a marked increase of ocean fertility. Besides, paleontological analyses show that this diversification episode correspond to the successive appearance of different, probably opportunistic Watznaueria species. The obtained fluxes of pelagic CaCO3 production, by far lower than those recorded in modern oceans, seems too low to have significantly impacted theMiddle Jurassic carbon cycle