Letteratura scientifica selezionata sul tema "Marine sediments South Australia Streaky Bay"

Modern sedimentation in the Gulf of Carpentaria is confined principally to marginal areas in water depths of less than 50 m. Within this zone, the distribution of sediments is irregular, being controlled by proximity to sediment sources and degree of exposure to waves and tidal activity. This is particularly so in the western gulf, where fluvial sediments supplied to Limmen Bight have been transported by waves and tides northwards beyond that embayment to accumulate in the sheltered environment of Blue Mud Bay. Limmen Bight is exposed to the south-easterlies, which produce sufficient wave action in the nearshore zone to prevent the widespread deposition of fine-grained terrigenous sediments. As a result, relict sand deposits occupy much of the floor of Limmen Bight in areas shallower than about 25 m. In deeper areas, terrigenous muds are deposited at a low rate over relict fluvial and marine sediments. The relict deposits accumulated in continental and nearshore marine environments during low-sea-level periods of the late Pleistocene.

Differences in phosphorus (P) availability can influence the ecology and physiology of seagrass communities; and are usually inferred from changes in the relative P content in seagrass leaves. Shark Bay is a subtropical marine embayment, with decreasing P concentrations in the water column and sediments from north to south across the entire embayment. We examined the P and nitrogen (N) content of seagrass leaves and P content of sediments across the Faure Sill and Wooramel delta region of Shark Bay, to determine whether the leaf content of seagrasses in Shark Bay also decreased from north to south over smaller spatial scales. Nutrient content of Amphibolis antarctica and Halodule uninervis were highly variable and were not strongly correlated with sediment P concentrations. Mean N : P ratios of seagrasses (<33.5) were not indicative of P limitation, as has been previously assumed for Shark Bay. We conclude that availability of P for uptake by seagrasses across Shark Bay may be highly localised and cannot be predicted from system-scale gradients (>100 km) of sedimentary P distributions. We suggest that P availability to seagrasses is more likely a complex function of differing nutrient inputs, rates of delivery to the plants and cycling rates.

"March 2002" Includes bibliographical references (leaves 145-161) An analogue for shallow marine carbonate sedimentation and deposition on a broad passive margin is described from the eastern Great Australian Bight.

"March 2002"
Includes bibliographical references (leaves 145-161)
xvii, 198 leaves : ill. (some col.), maps (some col.), plates ; 30 cm.
An analogue for shallow marine carbonate sedimentation and deposition on a broad passive margin is described from the eastern Great Australian Bight.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 2002

The aim of the research study is to apply mass spectrometric geochemical techniques to the investigation of palaeoenvironmental, chemostratigraphic and provenance questions from several South Australian Phanerozoic basins. Results of a multi-pronged palaeoenvironmental investigation of Early Cambrian marine sediments, employing trace and REE abundances, TOC and stable isotopes (C, S) are reported from three formations in the Stansbury Basins; Heatherdale Shale, Emu Bay Shale and Talisker Formation. The multiproxy approach in conjunction with sedimentological information provides a powerful tool for interpreting palaeoenvironmental conditions. Prevalent palaeoredox conditions of the Heatherdale Shale and Talisker Formation were dysoxic, evolving progressively more reducing natures up section. The Emu Bay Shale conversely demonstrates consistently aerobic interpretations for the redox proxies. Comparison of trace element and REE distributions to similar sequences of the Yangtze platform, South China shows striking similarities, Analogous basinal environments and common provenance may have lead to the seawater trace element chemistry of the Palaeo Pacific & Asian oceans exhibiting a homogenous nature. The Emu Bay Shale biota is the richest Burgess Shale-type (BST) fauna in the southern hemisphere. The implied oxic water column during accumulation appears difficult to reconcile with the exceptional preservation exhibited. Micro-scale sealed vessel (MSSV) pyrolysis of isolated kerogen and δ¹³Corg values provided confirmation of its redox status and implicate cyanobacteria in the preservation mechanism. Molecular signatures diagnostic of Gloeocapsomorpha prisca were identified, the first indication that microbial mats were involved in the taphonomy of a BST deposit. The biostratigraphic definition of GSSP horizons though the use of cosmopolitan taxa biohorizons is problematical for sections such as lower Cambrian deposits where few candidate fossils exist. Instead, an integrated approach comprising chemostratigraphy and/or sequence stratigraphy with the known biostratigraphy greatly increases our ability to make high-resolution correlations., δ¹³Ccarb profiles from three South Australian basins; the Stansbury, the Arrowie and the Officer are correlated regionally with the existing data from the Flinders Ranges. Globally identified excursions such as the negative ROECE and AECE event and the positive CARE and MICE events, are recognised in the profiles. This chemostratigraphic interpretation appears to support the biostratigraphic assignment of the sections. Asphaltic bitumens are long known to strand along coastlines of southern Australia and as far afield as New Zealand and Macquarie Island. Widely regarded as artefacts of an unidentified submarine oil seepages, a common source is interpreted from remarkably uniform compositions. An important consideration when attempting to locate their point of origin is the degree of weathering exhibited, which will reflect the residence time in the marine environment and proximity of the seep to the stranding site. Biomarker signatures and n-alkane C-isotopic profiles from interior and weathered exterior sub-samples of asphaltum from four localities in South Australia and New Zealand were compared. No distinction could be made between strandings despite their widely separated localities. The degree of degradation and isotopic variance suggest an origin from low intensity seeps in the western Otway Basin as strandings on the Limestone Coast and Kangaroo Island appear less weathered than those from Eyre Peninsula and New Zealand.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2012