The Belize margin, in the western Caribbean Sea, and Ashmore Trough, in the western Gulf of Papua, represent modern tropical mixed siliciclastic-carbonate depositional systems where significant masses of both river born terrigenous siliciclastics and neritic/pelagic carbonates accumulate at variables rates over space and time. This study examines variations in sedimentolgic and micropaleontologic parameters relative to late Quaternary sea level, climate, and paleoenvironment. This is accomplished through the evaluation of carbonate and siliciclastic accumulations, as well as planktic foraminiferal populations, of a 37.7 m giant piston core (MD02-2532) acquired from the slope of Gladden Basin adjacent to the Belize Barrier Reef, as well as benthic foraminiferal populations of two shorter (11.3 m) piston cores (MV-74 and MV-07/06) acquired on the slopes of Ashmore Trough, adjacent to the northern most extent of the Great Barrier Reef. Neritic carbonate fluxes to the slopes of Gladden Basin are largely regulated by sea level and consistent with well-established highstand shedding depositional concepts. Over the last ∼850 ka, neritic carbonate production (and export to the adjacent slopes) switches on when sea level floods the neritic carbonate regions and switches off when sea level falls and neritic carbonate regions are exposed. Siliciclastic accumulations are also controlled primarily by eustatic sea level fluctuations, with additional influences from local and regional variations in physiography, climate, and/or ocean currents. Planktic foraminiferal taxa of Gladden Basin are typical of tropical to subtropical populations and display significant variations in their downcore relative abundances, suggesting notable changes in surface water masses and oceanographic parameters over the last ∼630 ka. Temperature and salinity, often associated with glacial or interglacial intervals, appear to predominately influence the planktic foraminiferal populations. In Ashmore Trough, benthic foraminiferal relative abundances and multivariate analyses indicate three distinct assemblages whose proportions change over the last ∼83 ka. These assemblages signify distinct paleoenvironmental settings driven by organic carbon flux and sediment supply, as well as changes in sea level. Analysis of these late Quaternary mixed systems provides better understanding of their preservation in the rock record, particularly relative to sea level and sequence stratigraphic concepts.

Neogene sediments rich in siliceous microfossils, phosphate, and organic carbon formed simultaneously in many basins around the Pacific. This work focuses on these (and similar older) sediments from two basins of western South America (East Pisco and Sechura Basins) and studies the effects of tectonism, climate, and oceanic circulation on their formation. Transgressions inundated the East Pisco Basin during the late Eocene, late early Miocene, and late Miocene. Diatomaceous sediments formed during each transgression. Late Eocene diatomaceous sediments suggest that: upwelling off Peru dates from the late Eocene, a proto-Humboldt current existed during the Eocene, Antarctic cooling began before the latest Eocene, and the terminal Eocene event was the culmination of oceanic-climatic change. The late Eocene diatomites differ from overlying late Miocene sediments. Eocene diatomites are restricted to the western (offshore) margin of the basin, are separated from paralic sediments by a mud blanket, and were deposited well below wave base. Upper Miocene-Pliocene diatomites occur throughout the basin, grade into paralic deposits, and were deposited, in part, above storm wave base. The Sechura Basin experienced four transgressions between the Eocene and late Miocene. These transgressions formed four sedimentary sequences. Diatomaceous sediments are found in each sequence except the second (upper Oligocene-lower Miocene). In the third sequence (lower Zapallal Formation) diatomite-phosphorite became important between 14 and 8.1 Ma, and apparently reflects increased biogenic and decreased (?) terrigenous sedimentation rates. The increased biogenic accumulation rate reflects increased primary productivity or preservation. Sediments of the third sequence are separated from the fourth sequence by an angular unconformity (which correlates with subduction of the Nazca Ridge under the basin). Sediments of the fourth sequence differ from those of the third, and apparently record cooling and strengthened currents during the latest Miocene.

Floral and geochemical analyses were conducted on sinking and suspended particulate matter, and on sea ice and recent sediment samples from the northwestern Weddell Sea--northern Antarctic Peninsula area, and McMurdo Sound, in the southwestern Ross Sea. Data from McMurdo Sound reveal that although large numbers of diatom frustules dissolve within the upper water column the decrease in silica mass flux is much smaller. At mid-water depths, increases in the absolute flux of Nitzschia curta and Thalassiosira spp. indicate the influence of lateral advection. Within a near-bottom nepheloid layer additional dissolution occurs. Dilution and preferential dissolution is responsible for production of a surface sediment assemblage dominated by Thalassiosira spp. and Nitzschia curta. The surface sediment diatom assemblage in McMurdo Sound documents the seasonal history of sea ice extent and regional circulation patterns. Thalassiosira spp., indicative of water column primary productivity, is most common in eastern and northwestern McMurdo Sound, the result of advection from areas of open water. Nitzschia curta, a member of the sea ice microbial community and of ice edge blooms in the Ross Sea is most abundant in the southwestern Sound where the northward advection of oligotrophic water results in the dominance of the local flora. Maximum downcore Thalassiosira abundances occurred between 1600-1875 A.D., during the Little Ice Age. Warmer atmospheric temperatures or more persistent winds may have been responsible for more prevalent polynyas, suggesting that within the southwestern Ross Sea, the production of High Salinity Shelf Water, and hence Antarctic Bottom Water, may have been greater at that time. Measurements of water and acid soluble and insoluble phosphate performed on samples of suspended particulate matter from the Antarctic Peninsula region show the concentration of water-soluble, loosely bound organic phosphates decreases rapidly within the upper 100 m, the result of rapid phosphorus regeneration. A gradual decrease in insoluble organic phosphate signifies slower recycling of cell wall material. Acid-soluble phosphatic skeletal parts are transported efficiently. Concentration of insoluble phosphate increases in an eastern and southern direction as a function of increased influence of old Warm Deep Water containing higher levels of refractory organic material.

No description available.

Thesis (MAppSc)--University of South Australia, 1995

Thesis (MAppSc)--University of South Australia, 1995

Thesis (Ph.D.) -- University of Adelaide, Dept. of Geology, 1963. / Typewritten.

Thesis (Ph.D.)--University of Michigan, 2006. / (UMI)AAI3224898. Advisers: David K. Rea; Ben A. van der Pluijm. Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3655.

Thesis (Ph.D.)--Rice University, 2007. / (UMI)AAI3256669. Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1509. Advisers: Andre W. Droxler; Gerald R. Dickens.

Thesis (Ph.D.)--The Florida State University, 2007. / (UMI)AAI3263898. Source: Dissertation Abstracts International, Volume: 68-04, Section: B, page: 2206.