Thesis (Ph. D.)--University of Texas at Austin, 2002. / Includes bibliographical references. Also available in an electronic version.

Tephrochronologies for three marine core sequences from the Adriatic Sea have been constructed. Two of the sequences, PRAD 1-2 and RF93-77, are located in the central Adriatic and the third, SA03-03, lies in the southern Adriatic. Isotopic and biostratigraphic records are available for all three sequences, features of which have been used as isochronous markers in the region. This project aimed to establish whether tephra layers provide (a) secure, independent isochronous tie-lines and (b) a robust methodology for testing correlations based on other methods. A total of 54 tephra layers have been identified within these sequences, of which only 8 are visible layers, the remainder being classified as cryptotephras. Geochemical characterisation of the ash layers has been undertaken using electron microprobe analysis and laser-ablation trace element methods. Geochemical correlation to the detailed tephra record from Lago Grande di Monticchio was performed using chemical element biplots and discriminant function analysis. Bayesian-based age models were generated for the three Adriatic records using available chronological information that are independent of assumptions of synchroneity between proxy marker events. These models allowed comparisons with tephra and palaeoenvironmental data from Lago Grande di Monticchio and other Mediterranean sites. The results support some assumptions of synchronous regional changes, but not others. The key outcomes are (a) the recognition of additional (non-visible) distal ash layers that enhance the potential for correlating marine and terrestrial records in the central Mediterranean; (b) volcanic ash records preserved in Lago Grande di Monticchio and in some localities proximal to volcanic sources appear to be incomplete; and (c) isotopic records in Adriatic sediment sequences reflect regional forcing factors more than local conditions.

Horizons responsible for the reflection of seismic waves within deep-sea sediments are shown to be less reliable for the purposes of correlation than their counter-parts in shallow margin sequences. Similar surfaces, such as abrupt lithological changes and unconformities, in the two different realms are not neccessarily produced by the same processes. It is the nature of these processes which control the chronostratigraphic significance of a reflector. Thus reflectors may be correlated with reference to their genetic process. Horizons caused by time-restricted physical processes have enhanced chronostratigraphic significance. In the deep-sea, layers in which the physical properties change slowly with depth (transition layers) are also important for reflector formation. In as much as these transitions can be affected by temperature, pressure and sediment geochemistry, as well as time, the equation of an horizon at two different localities does not neccessarily imply correlation in time (i.e. the horizon is not neccessarily a chronostratigraphic time line). The two most important factors affecting impedance are the primary sedimentary geochemical composition and the nature of the grain to grain contacts within the sediment. Impedance increases with increasing grain density and increased rigidity of the sedimentary frame. The inter-dependance of all sediment physical properties greatly complicates the study of the relationships between them. Modelling can be used to demonstrate the affects of variation of individual properties. Synthetic seismograms can be generated using either physical properties data measured from discrete samples or from wire-line data. While quality is a limiting factor to the performance of .-. physical properties modelling, the latter is of value in that it enables modelling at many more localities than is possible with wire-line techniques alone. Abrupt impedance contrasts that produce reflectors important in deep-sea seismic stratigraphy may be grouped into a) Compaction horizons produced by gradual increase in over-burden pressure, b) Cementation horizons produced by variation in diagenesis with depth c) Calcite compensation depth (CCD) controlled horizons characterised by marked variation in primary sedimentary content and d) Unconformities produced by bottom current action.

No description available.

No description available.

The Canyon Range Formation (informal new name), formerly mapped as the Indianola Group within the Canyon Range, is divisible into two distinct, mappable units, A and B. Unit A is nearly all conglomerate strata, and conglomerate texture and sedimentary structures suggest an alluvial fan depositional environment. Precambrian and basal Cambrian quartzite clasts represent the erosional debris from the allochthonous Canyon Range thrust. Unit B is composed of interbedded fluvial sandstone and conglomerates with lacustrine limestones, commonly micritic and/or oncolitic. Conglomerate clasts indicate a Paleozoic carbonate provenance. Unit A, previously mapped as the Indianola, underlies Unit B and correlates with the Price River-lower North Horn Formations of the Pavant Range and Long Ridge. Marginal paleontologic and stratigraphic indicators suggest Unit B to be equivalent to the Paleocene-Eocene North Horn and Flagstaff Formations rather than the Cretaceous Indianola Group. Stratigraphic and structural relationships indicate the last major phase of "Sevier" thrusting ended by Price River (?) time.

<div>Paleozoic-Mesozoic stratigraphy exposed in the central Alaska Range includes a diverse assemblage of tectonostratigraphic basement terranes overprinted by late Mesozoic basin</div><div>formation and Cenozoic strike-slip displacement. In this thesis, I present a stratigraphic and structural framework for upper Paleozoic-Cretaceous strata exposed in Denali National Park and Preserve. The stratigraphic architecture of the study area is characterized by two distinct Upper Paleozoic-Mesozoic stratigraphic packages that are unconformably overlain by the Upper Cretaceous Cantwell Formation. Sedimentological, provenance, and geologic mapping data suggest that one basement assemblage, the Northern package, consists of Upper Triassic-Lower Cretaceous submarine strata deposited along the northwestern Laurentian margin. The other assemblage, termed the Southern package, is exotic to the ancestral continental margin and is associated with Permian-Upper Triassic submarine strata of the Farewell terrane. Provenance data from this package place new constraints on the Late Paleozoic paleogeographic position of the Farewell terrane prior to its accretion to the continental margin, likely by the Late Jurassic. The results of geologic mapping along the Toklat River corridor show that the Northern and Southern packages are deformed and structurally juxtaposed within a triangle zone bounded by the Hines Creek and Denali fault systems. This is the best exposure of stratigraphy associated with the Farewell terrane juxtaposed with strata representative of the ancestral continental margin known to date. New 1:24,000-scale geologic mapping coupled with a stratigraphic and provenance analysis of the Cantwell Formation provides new insights into sedimentation and deformation during the post-collisional phase of development of the Alaska Range suture zone (ARSZ). Results of this study define three stages of basin development. These stages are represented by alluvialfluvial, tidally influenced fluvial, and marginal marine deposits, respectively. Results of geologic mapping record progressive Late Cretaceous-Eocene deformation of the Cantwell Formation in a triangle zone and the transition from compressional to strike-slip tectonics in the Eocene. This deformation coincides with regional exhumation of the ARSZ and reconfiguration of the paleosouthern Alaskan margin with the establishment of the modern convergent margin configuration.</div>

No description available.

No description available.

Studies have documented spatially and temporally variable rates of surface subsidence across the Mississippi River delta plain of Louisiana. Variations in patterns and rates of delta plain subsidence may reflect subsurface distribution of compactionprone lithosomes. This research investigates historical changes in the surface geomorphology of the Caillou Bay headland in relation to the distribution of subsurface lithosomes. The stratigraphic framework was developed for the headland, and lithosomes were identified to establish the distribution of different sedimentary units. The geomorphic evolution as indicated by maps was then evaluated in order to locate patterns of shoreline change and wetland loss for the headland. Land loss maps developed were overlain on lithosome contour maps to calculate amounts of land loss overlying each lithosome contour interval. Analysis of results revealed that land loss was not uniform throughout the headland and that land loss patterns for several time periods varied as a function of the thickness of compactionprone lithosomes.