Upper Oligocene limestones up to c. 50 m thick form disconnected outcrops within a 20 km radius of Sciacca in southwest Sicily. Two facies are present: foraminiferal grainstone-packstones (dominatedby large benthonic foraminifera, particularly Lepidocyclines), and rhodolithic algal packstone-wackestones (in which eight species of coralline red algae are present). Petrology, fauna and flora indicate deposition in cool oxygenated waters of normal marine salinity at depths of 80-250 m in tropical subtropical latitudes; the two facies representing differences in local water depth and turbulence. Rare feldspars within the limestones are diagenetic, with a variable sodic oligoclase - calcic anorthoclase composition related to localised synchronous glauconitisation. The limestones rest disconformably on Cretaceous/Eocene carbonates, locally burrowed by Thalassinoid.es paradoxioa. A basal conglomerate contains both locally derived limestone cobbles and allochthonous phosphatised Eocene pebbles. All phosphate occurs as francolite re-placing limestone. Features of major, trace and Rare Earth elements clearly differentiate these phosphates from Lower Miocene phosphorites of both southeast Sicily and the Maltese islands, which have a very similar geochemistry. Lower Miocene limestones form similar outcrops generally to the north of the Upper Oligocene limestones and comprise a glauconitic limestone facies and a sandy limestone facies. Glauconite occurs as ubiquitous pellets, its geochemistry indicating formation by a gradational alteration of calcium carbonate. Petrology indicates deposition of the sediments in an outer shelf environment. Field relations of the two facies indicate that the Western Sicily Bridge (auot,) was a positive structural feature from basal Miocene times, acting as a barrier to the arenaceous Numidian Flysch facies derived from the west-southwest. Porosity of the Oligocene - Miocene limestones has been greatly reduced by compaction and by phases of both early submarine and latesubaerial diagenesis. Southward thrusting and associated folding post Lower Miocene times have slightly transported the sequences from their original (Saccense) carbonate platform and (Sicani) basin environments.

The Upper Oligocene Antigua Formation comprises a rapidly deposited sequence of limestones developed in an oceanic-arc setting immediately before cessation of subaerial volcanism. Ten sedimentary facies are recognized within it, ranging in depositional environment from shallow sublittoral to deep bank-slope. Their present outcrop patterns largely reflect original lateral facies variation across the ancient bank margin. The latter was mainly depositional in character, with bank-top often passing rather gradually into the upper bank-slope. Although a similar range and number of sedimentary facies are recognized within the Lower Miocene Anguilla Formation, bank-edge reefs are better-developed and the upper bank-slope shows evidence of sediment bypassing. Palaeoautecological and palaeosynecological studies of echinoid faunas can provide useful information on palaeoenvironment. Twenty genera and thirty-two species of echinoids are represented in the Antigua and Anguilla Formations. Of the species, five are entirely new, seven more are described for the first time from the Lesser Antilles, and a further three have their known ranges extended within the region. Of the genera, four were previously unrecorded as fossils from the Lesser Antilles, one, Irenechinus, being described for the first time outside Australasia. Twelve genera have their diagnoses and/or synonymies significantly modified from previously accepted usage. A new subgenus is erected for the earliest-known Caribbean representative of Tripneustes. Sedimentological evidence of hurricane activity within the Antigua and Anguilla Formations indicates that mid-Cenozoic sea-surface temperatures in the equatorial Atlantic were similar to those of the present day. Cenozoic echinoid biogeography supports an arc-migration model for the origin of the Caribbean Plate, indicates that speeds of shallow marine currents have increased during the Neogene (with the most significant changes affecting eastward Undercurrents), and suggests that a proto-Gulf Stream was in operation by Eocene times.

<p> Submarine-fan deposits form the largest sediment accumulations on Earth and host significant reservoirs for hydrocarbons. While many studies of ancient fan deposits qualitatively describe lateral architectural variability (e.g., axis-to-fringe, proximal-to-distal), these relationships are rarely quantified. In order to enable comparison of key relationships that control the lateral architecture of submarine depositional environments, I digitized published bed-scale outcrop correlation panels from five different environments (channel, levee, lobe, channel-lobe-transition-zone, basin plain). Measured architectural parameters (bed thickness, bed thinning rates, lateral correlation distance, net-to-gross) provide a quantitative framework to compare facies architecture between environments. The results show that sandstone and/or mudstone bed thickness alone or net-to-gross do not reliably differentiate between environments. However, environments are distinguishable using a combination of thinning rate, bed thickness, and correlation distance. For example, channel deposits generally display thicker sandstone beds than mudstone beds whereas levees display the opposite trend. Lobe deposits display the most variability in all parameters, and thus would be the most difficult to identify in the subsurface. I sub-classified lobe deposits to provide a more detailed analysis into unconfined, semiconfined and confined settings. However, the results for semiconfined lobes indicate that the degree of lobe confinement and subenvironment is not easily interpretable at the outcrop scale. This uncertainty could be partially caused by subjectivity of qualitative interpretations of environment, which demonstrates the need for more quantitative studies of bed-scale heterogeneity. These results can be used to constrain forward stratigraphic models and reservoir models of submarine lobe deposits as well as other submarine depositional environments. </p><p> This work is paired with a case study to refine the depositional environment of submarine lobe strata of the Upper Cretaceous Point Loma Formation at Cabrillo National Monument near San Diego, California. These fine-grained turbidites have been interpreted as distal submarine lobe deposits. The strike-oriented, laterally-extensive exposure offers a rare opportunity to observe bed-scale architecture and facies changes in turbidites over 1 km lateral distance. Beds show subtle compensation, likely related to evolving seafloor topography, while lobe elements show drastic compensation. This indicates more hierarchical method of compensational stacking as the degree of bed compensation is small compared to the degree of element compensation. Thinning rates and bed thicknesses are not statistically different between lobe elements. This signifies that the lateral exposure is necessary to distinguish lobe elements and it would be extremely difficult to accurately interpret elements in the subsurface using 1D data (e.g., core). The grain size, mudstone to sandstone bed thicknesses, element/bed compensation, and lack of erosion observed in the Cabrillo National Monument exposures of the Point Loma Formation are most similar to values of semiconfined lobe deposits; hence, I reinterpret that these exposures occupy a more medial position, perhaps with some degree of confinement.</p><p>

No description available.

The high elevated (ca. 1100 m) continental Kalahari Basin (KB) of southern Africa and the linked lower lying (ca. 400 m) Congo Basin (CB) of central Africa preserve in their interiors extensive sedimentary rock sequences and sediments that represent a unique record of the Phanerozoic geodynamic and climatic evolution of sub-Saharan Africa. In this thesis, field observations and new borehole data from the Democratic Republic of Congo (DRC) and Botswana are integrated with new paleontology and geochronology to present a substantially revised stratigraphy for the CB, and south-central Africa in general. This work also introduces a new multiphase model for the subsidence and uplift history of the CB, and improves correlations with the Cape-Karoo Basin (CKB) of South Africa and the Paraná Basin (PB) of south-east Brazil. Four deep boreholes, each between 2 and 4.5 km deep, drilled in the centre of the CB in the 1950’s and 1970’s are re-examined together with the colonial literature (in French) and available seismic data. This stratigraphic and basin analysis is complemented with new U-Pb dates of detrital zircons from core-samples of two of the boreholes (Samba and Dekese), as well as from samples collected during field work in the Kwango region of the south-west DRC. This work, for the first time, constrains the maximum ages and source provenances of the successions in the CB. Following the Pan African orogens (ca. 650-530 Ma), extensive sequences of red beds were deposited by regional paleocurrents to the south. These are now best preserved (1 km thick) along the West Congo, Oubanguides, and Lufilian Belts surrounding the CB. Overlying a hiatus that represents most of the early-Paleozoic, is a 1 to 3 km thick succession of easterly derived glacial, and then continental sequences of the Karoo Supergroup. This succession records the first main episode of subsidence [10-15 m/Ma], interrupted by a phase of uplift that is likely related to far-field intracontinental deformation within Gondwana supercontinent during the Variscan and Cape Fold orogenies (ca. 250-330 Ma) at its peripheries. Detrital zircons from the lower Karoo diamictites are dated at 1.85-2.05 Ga and 1.37- 1.42 Ga, and thus sourced from Paleoproterozoic (Eburnean) and mid-Mesoproterozoic (Kibaran type-I) basement rocks in Uganda and Tanzania. Zircons from all the other successions in the CB date predominantly at 950-1050 Ma and 500-800 Ma. These are derived from sediment recycling of late-Mesoproterozoic (Kibaran type-II) and late- Neoproterozoic (Pan African) sources in the Central African Republic (CAR) and Chad. A distinct unconformity across the Karoo Supergroup in the CB is overlain by 500- 1000 m Jurassic-Cretaceous sequences, here named the Congo Supergroup. During initial rapid subsidence [10-50 m/Ma], late-Jurassic (Kimmeridgian) shallow marine to continental sedimentation attests to a short transgression of proto-Indian Ocean waters into the northern CB (at 160 m above present day sea-level), succeeded by widespread deposition of aeolian dunes that extend from the southern CB to the PB in South America. The youngest zircons from these aeolian sediments in the CB date at 190 Ma and 240-290 Ma, and most likely indicate the influence of extensive silicic volcanic ash derived from the proto-Andes along the south-western margin of Gondwana. Two superimposed mid-Cretaceous (Albian-Cenomanian) lacustrine sequences in the central CB record a succeeding, slower [10-15 m/Ma], phase of basin subsidence during the opening of the South Atlantic (ca. 85-135 Ma). These Cretaceous sequences are in turn truncated by another regional peneplanation surface covered by Cenozoic (Eocene) silcretized sands and alluviums of the Kalahari Group, only 50-250 m thick in the centre of the CB. Southward, on top of the Kalahari Plateau in the central desert region of north-west Botswana, new boreholes intercepted laterally equivalent condensed lacustrine carbonates and calcretes (20-50 m thick) covered by sands. These terrestrial sequences are key archives of late-Mesozoic – Cenozoic paleo-climate changes, yet they remain stratigraphically unresolved. This new analysis of the Phanerozoic continental basins of south-central Africa and their equivalents in South America, opens a fresh continental-scale window into how West Gondwana break-up and concomitant epeirogenic uplifts of Kalahari (>2 km) and Congo (>200 m) are linked to interactions between the lithosphere and mantle geodynamics, and how these processes likely affected global climate changes.

<p>The Cretaceous-Paleogene Boundary Deposit is an impact-induced sedimentary deposit across the Gulf of Mexico basin, deposited due to the catastrophic effects of the Chicxulub Impact. The purpose of this project was to determine what the lithology and sedimentology evidence found in the Justiss Louisiana Central IPNH No. 2 well core from LaSalle Parish, Louisiana, tells us about the depositional history of the end-Cretaceous deposit and how the formation of this deposit was influenced by the effects of the Chicxulub Impact over 1000 km to the south. Project objectives were to characterize the end-Cretaceous sediments found in LaSalle Parish, Louisiana, to determine their depositional history as it relates to the Chicxulub Impact in Yucatan, Mexico, and to relate these onshore sediments to the basin-wide Cretaceous-Paleogene Boundary Deposit. A full description of the core was made and 35 thin sections from throughout the core were created and analyzed. Sedimentology evidence suggests that the end-Cretaceous chalk was deposited by seismically-induced mass wasting and later tsunami activity as a direct result of the Chicxulub Impact, and that the previously-proposed thickness of the Cretaceous-Paleogene Boundary Deposit may be overestimated.

The end-Ordovician was a critical time in Earth history and marked the occurrence of a mass extinction and a period of continental glaciation. The Ellis Bay Formation on Anticosti Island in Quebec represents up to 100 meters of relatively undisturbed, continuous, low latitude, shallow water carbonate ramp deposits that span the Hirnantian Stage and terminate close to the Ordovician-Silurian (O-S) boundary. In this study, approximately 400 samples of micritic limestones were collected from six Ellis Bay sections ranging from the basin margin to more distal basin center of the Anticosti Basin. delta13C and delta18O isotopic ratios were measured from these samples and integrated within a recently proposed framework of sequence stratigraphy and biostratigraphy for the Ellis Bay Formation. The measured delta13C values in most sections show a positive excursion (&sim;2&permil;) in the lower Ellis Bay Formation followed by a larger excursion (&sim;4&permil;) in the upper Ellis Bay Formation. The delta 13C profile of the Ellis Bay Formation on Anticosti Island exhibits a pattern similar to those of other profiles in graptolite-rich Hirnantian basinal successions from the rest of the world. The delta13C record on Anticosti Island is not consistent with predictions and observations based on current models that describe the state and evolution of the global carbon cycle during the Late Ordovician.

The &sim;608 Ma Old Fort Point Formation (OFP) is a unique, mixed siliciclastic and carbonate, stratigraphic marker that is exposed locally over an area of 35,000 km2 within the Neoproterozoic Windermere Supergroup (WSG) of the southern Canadian Cordillera. The OFP accumulated in bathyal to upper abyssal settings along the ancient western continental margin of Laurentia. It comprises three lithostratigraphic members that can easily be distinguished from the enveloping strata of the deep-marine WSG. The Temple Lake and Geikie Siding members are generally uniform in thickness and lithofacies and are interpreted to reflect basin-wide, synchronous deposition. These basal Ediacaran trangressive and highstand deposits, respectively, accumulated during a post-glacial eustatic rise that essentially shutdown the supply of coarse-graine siliciclastic sediment into the deep-marine part of the Windermere basin. Regionally widespread bottom-water anoxia developed during the post-glacial highstand and is indicated by prominent enrichments in organic carbon and seawater redox-proxies (e.g. Mo, V/Cr). Subsequent regional tectonic uplift and related relative sea-level fall is indicated by the diachronous deposition of the Whitehorn Mountain Member. Newly created sediment transport pathways such as submarine canyons, controlled the timing, location, and composition of Whitehorn Mountain Member strata which accumulated mostly during the ensuing relative sea-level rise. Limestone units of the OFP are characterized by negative delta 13C values that stratigraphically-upward exhibit a positive &sim;12&permil; shift, in addition to a 1 to 2&permil; shift towards more negative values from shallow to deep water environments. These results are similar to other globally distributed, basal Ediacaran transgressive post-glacial carbonates related to melting of the ca. 635 Ma terminal Cryogenian glacial event, including correlative WSG strata exposed in the Mackenzie Mountains, northern Canadian Cordillera. The physical and isotopic characteristics of the OFP are interpreted to be most consistent with the hypothesis of post-glacial upwelling and oceanic stratification.

Lake Tuborg is a large lake on west-central Ellesmere Island, Nunavut. Part of the lake is meromictic, and contains trapped saltwater below about 55 m depth. The lake receives meltwater and sediments from multiple sources, including snowmelt and glacier melt. A lake process study was undertaken from 2001-2003 at Lake Tuborg that involved obtaining profiles of water temperature, salinity, transmissivity, and dissolved oxygen. Networks of short and long sediment cores were also obtained throughout the lake. During the last year of monitoring the lake and its sediments, a large catastrophic drainage of an ice-dammed lake occurred (a jökulhlaup). This was the largest jökulhlaup witnessed in Canada since 1947. Detailed measurements of lake conditions before, during, and after the jökulhlaup allowed the responses to be measured in great detail. The lake drained by floating its ice dam, an extremely rare drainage style in the Canadian High Arctic. The basin of Lake Tuborg closest to jökulhlaup inflow filled with fresh, cold and turbid water. A sill separates this basin from the larger more distal meromictic basin, and this sill effectively blocked turbidity currents from entering this basin. Conclusions from this phase of research include (1) salinity and temperature in the saltwater basin were minimally affected by the jökulhlaup, and (2) at a deep, distal location, an identifiable thick, coarse-grained, non-erosive deposit was produced by the jökulhlaup. The above conclusions allowed the varved sedimentary record to be examined for similar deposits in the past, with the assumption that similar deposits could be found in the long core record, the sediments could be dated, and that previous jökulhlaup deposits would also be nonerosive. Varve-thickness counting, Cesium-137 dating, and particle size analyses showed that prior to 1960, no similar events occurred in roughly the last thousand years. In addition, only three large jökulhlaups have occurred in the last thousand years, all of which occurred after about 1960. This significantly improves the understanding of the history of the lake, the surrounding glaciers, and the paleoclimate of the region. The lake bottom deposits that were sampled before, during and after the 2003 jökulhlaup were extraordinarily unique. A major part of the work of characterizing these deposits involved determining the size of their constituent particles. Image analysis of sedimentary particles using backscattered electron microscope imagery is a method to determine particle size at extremely high resolution. This tool improves on existing techniques since it automates the process of statistically processing images, quantifies the percentage of disturbances on images, and allows for extremely small measurement windows relative to particle size by implementing special particle counting rules.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Geological Sciences and Environmental Studies, 2007. / Includes bibliographical references (leaves 308-314).