A chronostratigraphic subdivision of the Upper Jurassic synrift sediments in the eastern Barrow Sub-basin was developed from the integration of core logging, petrography, well log sequence analyses and seismic stratigraphy. From this basis, the Callovian to base Cretaceous sediments may be subdivided into five depositional sequences. The development of the sequence boundaries, in most part, is closely related to periods of major changes in basin configuration associated with the sequential breakup of eastern Gondwanaland. Initiation of the Upper Jurassic rift complex occurred during late Callovian early Oxfordian associated with the development of a northeast-southwest trending spreading centre on the Argo Abyssal Plain. The spreading centre propagated southwards during the Late Jurassic. This resulted in active rifting in the Barrow Sub-basin and ultimately led to the separation of the Indian and Australian plates during Valanginian time.Upper Jurassic synrift sediments in the eastern Barrow Sub-basin consist of detached basin floor fan complexes, channelised and canyon fed fan systems, slump deposits, prograding outer shelfal to slope deposits and deep marine claystones. Post-depositional uplift of the eastern shelfal areas during the Late Jurassic resulted in erosion of the transgressive and highstand fluvial-deltaic to shelfal deposits. These periods of uplift and erosion provided much of the sediment redeposited in the basinal areas during the lowstand periods. Seven sandstone facies were recognised in the Upper Jurassic sedimentary section based on core control. Each sandstone has unique reservoir characteristics which can be related to the depositional setting. / The abundance of glauconite and belemnites combined with ichnology and biostratigraphic assemblages associated with marine environments, indicate that deposition of all the sandstone facies occurred within an outer shelfal - deep marine environment. Reservoir quality was best developed in the dominantly medium grained, moderate - well sorted sandstones, (facies 7), which were deposited as detached, basin floor submarine fan sands or interbedded turbidites. In contrast, reservoir quality was relatively poorly developed in the remaining facies which were deposited as slope fans, slumps, or distal turbidite deposits.The abundance of quartz and presence of banded iron, jasper, and potassic feldspar grains support the provenance for the basinal sandstone facies being the Precambrian alkyl granites and banded iron formation of.the Pilbara Shield and Hammersley Ranges. These Precambrian igneous rocks and metasediments mark the eastern boundary of the Barrow Sub-basin study area. To predict the distribution of sedimentary facies in the Upper Jurassic synrift sediments of the eastern Barrow Sub-basin, the interplay between the major controlling depositional processes, namely tectonics, sediment supply and eustasy must be understood. Subdivision of the synrift sedimentary section on the basis of lithostratigraphy can be misleading and does not adequately resolve the facies relationships observed in the well intersection. The results of this research form the basis for a regional sequence analysis and seismic stratigraphic study.

Opening-mode fracture shapes are typically the result of brittle deformation and proportional growth in fracture height, length, and width. Based on the typical fracture shape, it is assumed that fracture tips are free to propagate in all directions. Some natural rock fractures have been shown to form as a result of slow non-elastic deformation processes. Such fractures may propagate to a finite length or height and accommodate further growth by aperture widening only. To determine the growth conditions of a fracture in the Triassic-Jurassic La Boca Formation of northeastern Mexico and to test fracture growth models, I combined fluid inclusion microthermometry and SEM-based cathodoluminescence cement texture analysis to determine the relative timing of fracture cement precipitation and related fracture opening for five samples collected along its trace. Fracture growth initiated at a minimum age of 70 Ma as two separate fractures with branching fracture tips that coalesced to a single continuous fracture under prograde burial conditions at a minimum age of 54 Ma. At this stage, fracture growth was accommodated by both propagation (i.e. increase in trace length) and by an increase in aperture during maximum burial and early exhumation. Samples collected at the fracture tips recorded temperatures reflecting fracture opening starting with maximum burial at a minimum age of 48 Ma at one tip and of 38 Ma at the other tip. Synkinematic fluid inclusions in crack-seal cement track continued fracture opening close to the fracture tips without a concurrent increase in trace length after 38 Ma until about 21 Ma. I attribute the observed change in fracture growth mechanism to a change in material response. The stage in aperture increase without propagation corresponds to an increase in elastic compliance or in non-elastic flow properties. Non-elastic flow can be attributed to solution-precipitation creep of the host rock. Dissolution of host quartz grains and subsequent quartz precipitation is consistent with the abundance of quartz fracture cement formed during exhumation. Cement textures from fractures in the La Boca Formation mimic those found in subsurface core, which allows application of the results to a variety of geologic environments. / text

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The Middle Jurassic Entrada Sandstone of the Four Corners region, USA, is composed predominantly of very fine-grained, red, silty sandstone with poorly defined sedimentary structures. The origin of this facies is enigmatic, even though it is common both on the Colorado Plateau and globally, and is spatially situated between deposits recording unambiguous marine and aeolian environments. Eleven sections were measured along an 85 km transect from the Blanding Basin in southeastern Utah to the San Juan Basin in northwestern New Mexico. Outcrop and laboratory analyses distinguish eight facies: (1) silty shale, (2) shallow subaqueous reworked, fine- to medium-grained sandstone, (3) brecciated, very fine-grained sandstone, (4) crinkly laminated, very fine-grained sandstone with preserved wind ripples and abundant silty laminae, (5) weakly laminated, fine-grained sandstone with occasional silty laminae, (6) planar-laminated, fine-grained, wind-rippled sandstone, (7) cross-stratified, fine- to medium-grained aeolian cross-stratified sandstone, and (8) micritic limestone. Lateral and vertical relationships of these facies show a proximal to distal transition from cross-bedded wind-lain facies to loess-dominated sabkha facies with increasing abundance of water-lain facies basinward. The well known Todilto Limestone (facies 8) is situated stratigraphically below loess-dominated sabkha facies (facies 4 and 5) within the Entrada Sandstone, reinforcing previous interpretations that the unit represents a catastrophic flooding event and not a local groundwater flux. / text

No description available.

Samples of shallow-water carbonates were collected from Jurassic and Cretaceous Italian carbonate platforms and subjected to petrographic, diagenetic and chemostratigraphic analyses (⁸⁷Sr/⁸⁶Sr, δ¹³C_carb, δ¹³C_org, δ¹⁸O). In general, the new chemostratigraphic data generated reflect trends established by previous work, some of which has been carried out on biostratigraphically calibrated reference sections. Consequently, chemostratigraphic correlations (⁸⁷Sr/⁸⁶Sr, δ¹³C_carb) of isotope profiles taken from platform carbonates with well-dated reference sections have allowed the application of high-resolution dating frameworks to the biostratigraphically poorly constrained carbonate platforms. The increased resolution in dating of the Italian carbonate platforms has, furthermore allowed a detailed investigation into the facies response of these carbonate platforms to major geological events. In particular, platform responses to oceanic anoxic events and other periods of major perturbation in the global carbon cycle are analysed (early Toarcian, Aalenian-Bajocian, Oxfordian-Tithonian, Valanginian-Hauterivian, Aptian-Albian, Cenomanian-Turonian, Coniacian-Santonian). Lower Jurassic levels of the Trento Platform record platform devastation in the early Toarcian synchronous with a major negative δ¹³C_carb excursion, followed by platform recovery synchronous with a pronounced δ¹³C_carb positive excursion and return to background values. The Campania-Lucania Platform shows negligible response to the oceanographic events of the early Toarcian even though the characteristic carbon-isotope profile is readily identifiable. The Trento Platform drowned at approximately the Aalenian-Bajocian Stage boundary, synchronously with a reproducible negative followed by positive δ¹³C_carb excursion, whereas the Campania-Lucania Platform underwent a facies transition from oolite to cyclically bedded micrite. The Friuli Platform showed negligible depositional response to the carbon-cycle perturbations of the Kimmeridgian-Tithonian, Valanginian-Hauterivian, Aptian-Albian and Cenomanian- Santonian (as registered in the δ¹³C_carb record). The Campania-Lucania Platform registered flooding and increased levels of organic-matter preservation coincident with pronounced positive δ¹³C_carb excursions at Cenomanian-Turonian and Coniacian-Santonian levels. Observations on the responses of carbonate platforms to oceanographic conditions during periods of global carbon burial lead to the conclusion that temperature excess is a hitherto neglected control on global carbonate accumulation rates.

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Abstract: This palynostratigraphic study of Mesozoic successions in hydrocarbon-prospective Tanzanian coastal basins utilizes cores, ditch cuttings, and outcrop samples. These contain rich and diverse dinoflagellate suites ranging in age from Middle Jurassic (Bajocian) to earliest late Cretaceous (Cenomanian). Spores and pollen grains are also recorded, but these are, with some exceptions, subordinate to the dinoflagellate components.In the systematic section, one new dinoflagellate cyst genus, Kipatimudinium, is formally described and nine new species are established: Amphorulla ruvuense, Dichadogonyaulax mandawaense, Egmontodinium annaiae, Hystrichodinium playfordii, Kipatimudinium foliatum (type species), Limbodinium patulum, Pseudoceratium redactum, Sentusidinium tanzaniensis, and Yalkalpodinium africanum. Six, informal, stratigraphically successive dinoflagellate assemblages are distinguished:Assemblage I (Bajocian-Bathonian); Assemblage II (Callovian); Assemblage III (Oxfordian); Assemblage IV (Kimmeridgian-Tithonian); Assemblage V (Berriasian-Barremian); and Assemblage VI (Aptian-Cenomanian).Coastal Tanzania appears referable to the Austral dinoflagellate realm due to the presence of, inter alia, Broomea ramosa, Komewuia glabra, Wanaea clathrata, and Wanaea digitata. Some minor biostratigraphic anomalies are noted, including the introduction of Glossodinium dimorphum; this is datable as early Oxfordian in Tanzania whereas in Australasia the species appears earlier (in the Callovian). A few noteworthy quantitative phenomena are evident; for instance, the abundance of Lithodinia jurassica in the vicinity of the Callovian-Oxfordian boundary and the marked increase of Wanaea spp. in the Oxfordian, specifically in the Ruvu Basin of the northern coastal belt. These events are of chronostratigraphic significance and could be applicable to regional correlation. Middle-Late Jurassic assemblages show a conspicuous degree of cosmopolitanism, and include some species previously considered to be restricted to certain regions in the low and high latitudes.The Early Cretaceous (Berriasian-Barremian) assemblages show close affinity to the Tethyan Realm. The latest Early Cretaceous (Albian) to earliest Late Cretaceous (Cenomanian) strata are allied to the Albian-Cenomanian Elaterates province. The presence of elater-bearing pollen in offshore and onshore sections of Tanzania indicates that the elaterates had a wider geographic distribution than previously reported: i.e., extending beyond the northern part of the African and South American continents.The lower part of the Kipatimu Formation, which contains Assemblage IV, yielded Komewuia glabra, Broomea ramosa, and Rigaudella aemula and their presence precludes the Early Cretaceous age previously ascribed to this part of the formation. Likewise the Makonde and Mkindani Beds have yielded typically Early Cretaceous pollen grains including Classopollis braziliensis, Retitricolpites vulgaris, and Elaterocolpites castelainii.The Jurassic/Cretaceous boundary is coincident with the upper limit of Assemblage IV based on the last appearances of, in particular, Komewuia glabra and Rigaudella aemula. Within the Kipatimu Formation (as represented in wells SS-5 and SS-7), the systemic boundary appears conformable. But elsewhere in the coastal belt, the boundary is clearly unconformable.On the basis of palynostratigraphic data, significant biostratigraphic events, such as introductions and exits of certain dinoflagellate species often match sequence boundaries.From palynofacies analyses and palynostratigraphic data the Kipatimu Formation is dominated by phytoclasts indicating high terrestrial inputs during its deposition. Abundance of black wood (of high buoyancy) in the majority of samples implies high energy settings and abundance of brown wood (less buoyant) is an indication of a sudden terrestrial input into the marine system. The organic composition of sedimentary rocks is an important means of which the depositional history of the enclosing sediments can be understood. Different environmental settings clearly influence the character of palynofacies. For example, abundant chorate cysts (e.g., Systematophora spp.) in samples from the upper sections of SS-5 suggest open marine settings. Therefore, palynofacies analyses can be viewed as providing useful pointers to interpreting the environmental circumstances in which the rocks, in this case the Kipatimu Formation, were deposited.

Thesis (M.A.)--State University of New York at Binghamton, Department of Art History, 2009. / Includes bibliographical references.