The Titus Canyon Formation : evidence for Early Oligocene extension in the Death Valley Area, CA

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Title as it appears in the M.I.T. Graduate List, Sept. 1991: Analysis of the Titus Canyon Formation, evidence for Early Oligocene extension in the Death Valley Area, California.Includes bibliographical references (leaves 48-50).by Beverly Z. Saylor.M.S

Subsurface Relationships between the Sebree Trough and Carbonate-Siliciclastic Mixing in the Upper Ordovician Lexington-Trenton and Point Pleasant-Utica Intervals in Ohio, USA, using Multivariate Statistical Well Log Analysis

The Upper Ordovician (lower Katian; upper Chatfieldian-lower Edenian) Lexington-Trenton limestone and Point Pleasant-Utica shale intervals are important subsurface stratigraphic units across Ohio as they are the sources of significant conventional and unconventional hydrocarbon resources. However, both units exhibit anomalous distributions across the state and heterogeneous relationships, especially in areas where they intertongue. The limestone units show a peculiar SW-NE thinning trend across Ohio, whereas the overlying shale units show an anomalous thickening along the same trend—a trend associated with the poorly understood Sebree Trough, a supposed Late Ordovician paleobathymetric low related to the coeval Taconic Orogeny. To explore relationships amon Lexington-Trenton carbonates, Point Pleasant-Utica shales, and the presumed Sebree Trough, multivariate statistical analysis was used to compare geophysical well logs across the state with well logs referenced to the mineral content of 4 Lexington-Trenton-Point Pleasant-Utica cores. Comparing well-log responses with the mineral content of the reference cores allowed the discernment of 10 electrofacies, keyed to lithofacies in the cores. Software analysis of many other well logs across the state then made electrofacies assignments by comparing well-log responses from the other wells with well-log responses from the reference cores preset into the software. Electrofacies responses were color-coded, mapped in wells at 0.6 m (2 ft) resolution, and used to make section lines and isopach maps of similar electrofacies. Isopach maps and cross sections confirm the presence of the Sebree Trough across Ohio, with trends that parallel existing and projected basement structures. This suggests that the Sebree Trough in Ohio was a bathymetric low, which was, at least in part, controlled by reactivation of basement structures due to far-field Taconic stresses

A composite reference section for terminal Proterozoic strata of southern Namibia

Integrated sequence stratigraphic and chemostratigraphic data yield a framework for correlations of stratigraphic units in the terminal Proterozoic to Cambrian Witvlei and Nama Groups of Namibia. Coupled with precise U-Pb zircon age constraints, these correlations make it possible to construct a composite reference section for use in calibrating terminal Proterozoic chronostratigraphy. The Namibian reference section starts with two distinct glacial horizons and extends up to within 1 million years of the Proterozoic-Cambrian boundary. The two glacial horizons may represent each of two distinct Varanger-age glaciations better known from the North Atlantic region. From the higher of the two glacial horizons up, the composite stratigraphy preserves one of the thickest and most complete available records of carbon-isotope variability in post-Varanger terminal Proterozoic seawater. Four carbon-isotope chemostratigraphic intervals are recognized: (1) a postglacial negative δ^(13)C excursion (Npg interval); (2) a rising interval (Pr interval) of increasing positive delta 13 C values; (3) a falling interval (Pf interval) characterized by decreasing positive δ^(13)C and culminating in near zero or negative values; and (4) an interval of moderately positive, relatively invariant δ^(13)C values (I interval) that extends up to the unconformity that contains the Proterozoic-Cambrian boundary. Each of these chemostratigraphic intervals can be recognized in widely separated correlative sections around the world. By comparing sediment accumulation rate in the radiometrically calibrated Namibian stratigraphy with sediment accumulation rates in correlative sections in Arctic Canada and Oman, a maximum age of 564 Ma is estimated for the end of the younger Varanger glaciation, 25 m.y. younger than previous estimates

Sequence stratigraphic and chemostratigraphic constraints on the evolution of the terminal Proterozoic to Cambrian Nama Basin, Namibia

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.Includes bibliographical references (p. 117-124).by Beverly Z. Saylor.Ph.D

The Youngest Ediacaran Fossils from Southern Africa

Discovery of fossils of the Ediacara biota near the top of the Spitzkopf Member at farm Swartpunt extends the known range of these remains in Namibia more than 600 m to near the sub-Cambrian unconformity. The fossiliferous beds occur approximately 100 m above a volcanic ash dated at 543 ± 1 Ma, and thus may be the youngest Proterozoic Ediacara-type fossils reported anywhere in the world. Fossils are preserved within and on the tops of dm-thick beds of storm-deposited sandstone at two stratigraphic levels; the environment is interpreted as open marine, generally calm but with episodic disruptions by storm waves, and probably within the euphotic zone. The presence of Pteridinium carolinaense( St. Jean), which is also known from the classic sections in Ediacara and the White Sea among others, reinforces evidence from geochronology and chemostratigraphy that the Swartpunt section is terminal Neoproterozoic in age. The new genus and species Swartpuntia germsi is a large, multifoliate frond that exhibits at least three quilted petaloids. Macroscopically, Swartpuntia resembles Pteridinium and Ediacara-type fronds such as Charniodiscus traditionally interpreted as Cnidaria, whereas microscopically it exhibits segmentation that is remarkably similar to that of the putative worm Dickinsonia. Combination of diagnostic characters of these supposedly disparate groups in a single species suggests that many species of quilted Ediacaran organisms were more similar to each other than they were to any modern groups, and provides support for the concept of the "Vendobionta" as a late Neoproterozoic group of mainly multifoliate organisms with a distinctive quilted segmentation

Supplementary Material for "Subsurface Relationships between the Sebree Trough and Carbonate-Siliciclastic Mixing in the Upper Ordovician Lexington- Trenton and Point Pleasant-Utica Intervals in Ohio, USA, using Multivariate Statistical Well Log Analysis"

The Upper Ordovician (lower Katian; upper Chatfieldian-lower Edenian) Lexington-Trenton limestone and Point Pleasant-Utica shale intervals are important subsurface stratigraphic units across Ohio as they are the sources of significant conventional and unconventional hydrocarbon resources. However, both units exhibit anomalous distributions across the state and heterogeneous relationships, especially in areas where they intertongue. The limestone units show a peculiar SW-NE thinning trend across Ohio, whereas the overlying shale units show an anomalous thickening along the same trend—a trend associated with the poorly understood Sebree Trough, a supposed Late Ordovician paleobathymetric low related to the coeval Taconic Orogeny. To explore relationships among Lexington-Trenton carbonates, Point Pleasant-Utica shales, and the presumed Sebree Trough, multivariate statistical analysis was used to compare geophysical well logs across the state with well logs referenced to the mineral content of 4 Lexington-Trenton-Point Pleasant-Utica cores. Comparing well-log responses with the mineral content of the reference cores allowed the discernment of 10 electrofacies, keyed to lithofacies in the cores. Software analysis of many other well logs across the state then made electrofacies assignments by comparing well-log responses from the other wells with well-log responses from the reference cores preset into the software. Electrofacies responses were color-coded, mapped in wells at 0.6 m (2 ft) resolution, and used to make section lines and isopach maps of similar electrofacies. Isopach maps and cross sections confirm the presence of the Sebree Trough across Ohio, with trends that parallel existing and projected basement structures. This suggests that the Sebree Trough in Ohio was a bathymetric low, which was, at least in part, controlled by reactivation of basement structures due to far-field Taconic stresses

Stages of palaeoenvironmental evolution, climate, and sea level change of the Niger Delta - East Equatorial Atlantic: Novelty from elemental tracers, sedimentary facies, and pollen records

This Study Used the Comparative Analysis of 3 Gravity Cores (GCs) Obtained from the Shallow Offshore at ~40 M Water Depth to Reconstruct the Morphological Evolution of the Delta (East Equatorial Atlantic). the Focus of This Study is on the Interpretation of Elemental Tracers and their Justification between These Tracers and Microfossil Data to Understand the Impact of Climate-Sea Level Controls on the Evolution of the Niger Delta during the Late Quaternary. Key Elemental Tracers Comprising Ti, Zr, Fe and S Were Explored to Strengthen This Concept. High Ti/Zr Ratio Values Down-Hole Indicate Fluvial Transport of Terrestrial Components to the Marine Setting (20–11.7 Ka), Whereas High Values of Fe/S Ratio Up-Hole Provide an Extent of Inherent Marine Shale of the Niger Delta (11.7–6.5 Ka). in Addition, the Integrated Multiple Proxy (Mangrove and Hinterland Pollen, Planktonic Foraminifera and Sedimentary Facies) with Elemental Tracer Ratios Provided Robust and Coherent Information for Delineating the Late Glacial (MIS2) Prograding and Interglacial (MIS1) Retrograding Deltaic Transition, Respectively. the overall Trends of the Two Elemental Tracer Ratios (Lower and Mid-Upper Depths of the GCs) Provide a New Distinction on the Depositional Patterns (Prograding and Retrograding Delta) to Determine the Proximal/upper (Clay, Silt and Very Fine Sand) and Distal Offshore/lower Shorefaces (Coarse-Medium Sand), and Gross Palaeoenvironments based on Planktonic Foraminifera Records. These Sequential Records Provide a New Clue as Evidence of the Morphological Evolutionary Stages (Delta Plain, Delta Front and Prodelta) of the Niger Delta Landscape, Gross Palaeoenvironments, and Vegetation Dynamics (Pollen Data) during Two Distinct Time-Bound Intervals (20–6.5 Ka), Which Potentially Delineate the Climate and Sea Level Regime of the Coastal Offshore