The small, high sediment yield Waipaoa River is located on the tectonically active, mountainous Poverty Margin on the east coast of the North Island, New Zealand. In contrast to sedimentary sequences on passive margin shelves, active margins, such as the Poverty Margin, can preserve continuous records of changing geological and environmental conditions at the land-sea interface during rapid sea-level rise. Two subsiding mid-shelf basins on the Poverty Shelf contain thick transgressive sequences which provide a record of evolving river, climate, landscape, and oceanographic conditions since the Last Glacial Maximum (LGM). This dissertation investigates the stratigraphic development of Poverty Shelf, including event layer preservation, over the last ∼14ka using geochemical proxies and physical properties analyses of the sedimentary record. The work herein was conducted under the auspices of the MARGINS Source-to-Sink program, a multi-national, interdisciplinary study focused on understanding sediment routing, transformation and fate through the Waipaoa Sedimentary System (WSS) from catchment sources to final sinks on the adjacent Poverty Shelf and Slope. A suit of five giant piston cores and eight box cores were retrieved from Poverty Shelf during two cruises to address long (Holocene) and short (modern) timescales, respectively, of deposition. Geochronological, geochemical and sedimentological profiles from the giant piston cores are used to reconstruct the processes that influenced shelf infilling during this critical period of recent earth history. Accumulation rate analyses from high-resolution radiocarbon profiles and tephrachronology, along with X-radiographic facies analysis, enable tracking of rapidly shifting loci of deposition from the slope to mid-shelf depocenters. Grain size profiles and delta13C values reveal sympathetic changes that track the waxing and waning influences of sediment supply via the Waipaoa River as sea level rose to maximum flooding at ∼7ka, subsequent Poverty Bay shoreline reorganization and changing shelf accommodation, and, in the last ∼1ka, a strong anthropogenic signal. Imprinted upon this record is evidence for temporal and spatial changes in event layer frequency and type throughout the Holocene. Event layers may be produced by extreme and episodic storms, floods, earthquakes and other perturbative events that punctuate background marine sedimentation with large additions of terrestrial sediment. Event layers can be identified by unique textural and geochemical characteristics. An event layer, likely emplaced via hyperpycnal flow, attributed to Cyclone Bola (1988), the most severe modem cyclone on record in this location, serves as a modem benchmark for other storm events in the Poverty Shelf records. Examination of X-radiographs and lithostratigraphy, textural and isotopic variability reveal that the Poverty Shelf stratigraphic record preserves evidence of exceptional event sedimentation in the past and present that can be distinguished from shifts in supply, transport, and accumulation of sediments due to longer-time scale perturbations related to climate, sea level, and tectonics. A period of increased fidelity of the event record in the mid-Holocene is observed associated with increased accommodation within rapidly flooded depocenters.

The study area is located along Highway 20 east Cartersville Georgia, where outcrops of the Weisner Formation are exposed. The section consists of two main facies, the sandstone facies and shale facies. Parallel lamination and cross stratification are commonly observed sedimentary structures at this location. Petrographic study reveals that the grains in the sandstone are dominantly quartz, and to a smaller extent feldspar and mica. The shale facies is rich in Al2O3 and K2O compared to the sandstone facies. No fossil is observed in any of the two facies. Petrographic studies also indicate igneous, metamorphic, and sedimentary source rocks for these clastic rocks. The shale facies is very rich in mica, with muscovite and some kaolinite. Lithologic features and grain size suggest that the Weisner Formation was probably deposited in a shallow marine environment.

Present models suggest that fluvial and marine depositional patterns were distinct from modern patterns prior to the appearance of land plants. Although these models are likely correct, problems exist when one attempts to distinguish between fluvial and shallow marine deposits in pre-Silurian strata, making it difficult to accurately determine depositional patterns. The lack of land plants and scarcity of body and trace fossils, especially in Precambrian and early Cambrian strata, make identification difficult. Based on core data and limited outcrops, the Lower Hickory Sandstone, a late Cambrian sandstone, has been interpreted to progress from fluvial to shallow marine. These data have allowed the development of an overall depositional model, but minimal detail of facies changes is available. Based on the limited data, both deltaic and estuarine models have been suggested for the Lower Hickory. Mining of the Lower Hickory for frac sand has created highwalls in the CarmeuseNA Mine, which provides an opportunity to study facies changes at this site. The CarmeuseNA Mine, located in McCulloch County, Texas, has exposed the formation along ~500 m long and 20 m-high faces, respectively. Because of limited exposure, only the south and west walls, as well as part of the east wall, could be examined. Digital photographs of the faces were mosaiced using standard photogrammetrical practices to produce visual representation of the highwalls. Bedding geometry was then mapped on the digital images to facilitate a detailed interpretation of the depositional process. Core and well data were used to map Hickory thickness to produce an isopach map. Four primary facies were observed in the quarry, dominated by small-scale and large-scale cross-bedding. Paleocurrents are generally unidirectional to the southsoutheast indicating a braided fluvial origin, but rarely opposing directions are seen. Bioturbation is rare low in the section, but increases upwards. Together with the rare herringbone cross-bedding, clay drapes, and bioturbation, a tidal influence is strongly suggested. The model suggested is a braided stream setting influenced and reworked by tides. A braided-delta fed by braided streams guided by a ridge and swale-dominated setting, which served as the sediment supply for the delta, is proposed.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

No description available.

The Paleocene submarine fans of the Central Graben represent important petroleum reservoir units recording the cyclic input of sand-rich turbidity flows into the post-rift basin. Provision of extensive seismic (a subset of ~l5000 km" of the PGS Central North Sea MegaSurvey), well (n = 549) and core (n = 28, totalling ~2760 feet/84l m) datasets by Shell UI Europe enabled a regional-scale re-evaluation of these deposits. This thesis presents new models illustrating the distribution and quality of the Maureen and Lista Formation sandstones and the syn- and post-depositional controls on these deposits. The Lista Formation sandstones occur within northwest (channelised, proximal, ~300 feet net) to southeast (sheet-like, distal, ~50 feet net) trending (axial) fans with western/eastern fairways and minor sidefan sedimentation (west/east). Four sand-rich to sand-poor facies are defined, with distinct grain size distributions. Mean grain size is the main control on porosity and permeability. Progradation occured between the Ll and L2 units with retrogradation in the L3. This variability, and internal porosity trends, is linked to global sea level change. Characterisation of the Maureen Formation sandstones is complicated by the presence of variable chalk facies derived from turbidite, debris flow and pelagic processes. However, these deposits can still be classified in a similar manner to the Lista Formation and exhibit similar spatial distributions, although the sandstones are thinner ~125 feet in the northwest to 25 feet in the southeast, suggesting that similar depositional controls were active. Sandstone quality is controlled by grain size (with calcitisation also important) although the porosity/permeability values are lower than in the Lista Formation. Progradation occured between the TlO and T20/30 sequences with retrogradation in the T35. The current MlIM2 divisions do not describe the complexity of this formation. The routing of the sandstones was defined by the relict graben structure with offset stacking an additional local control. Routing from the shelf to the basin was controlled by global sea level change. Although these systems are often labelled as basin floor fans they do not resemble classical examples, thanks to their confined nature.

The Upper Albian (mid-Cretaceous) sediments of the Anglo-Paris Basin display a range of condensation phenomena, including glauconitic and phosphoritic sands, glauconitic intraformational pebble beds, and mineralised nodular hardgrounds. These are interpreted as the result of sedimentation rate fluctuations controlled by small-scale relative sea-level changes of at least regional nature. The regional signal was modified by local tectonics, including occasional synsedimentary faulting and the development of thinned successions and complex condensation horizons over broad submarine highs. Candidate sequence boundaries, marine flooding surfaces and systems tracts are proposed. Episodic, high-energy storm events record a spectrum of storm intensities and periodicities in the Upper Greensand Formation. Storm processes interacted with early submarine lithification to produce a suite of pebble-shell beds, simple and amalgamated coquinas, and storm-scoured hardgrounds. Analysis of shell bed fabrics and taphonomy indicates the important role of high-energy storms in generating a distinct event stratigraphy. Stable isotope analysis has detected a positive secular change in carbon-isotopic ratios within carbonates of dispar zone age, resolved as two smaller positive shifts across nodular hardgrounds. This correlates with the development of organic-rich sediments in a range of settings world-wide. Analytical problems, including silica diagenesis, have been addressed by a series of parallel control studies. Geochemical and petrographic analysis has confirmed the widespread development of glauconitic minerals throughout the Upper Greensand, and has been used to investigate grain evolution in a range of lithologies. A review of the global development of the Cretaceous glauconitic facies has been used to compile depositional models for a range of settings. Volumetric calculations of Cretaceous glauconite production rates have shown secular changes, with peak Aptian to Santonian values linked to transgressions across the broad shelf seas which developed globally during this time of rising sea-levels and sea-level highstand.

No description available.

No description available.

No description available.