Showing papers by "Ken J. Woolfe published in 2000"

Facies analysis and sequence stratigraphy of CRP-2/2A, Victoria Land Basin, Antarctica

Abstract: The Oligocene to Quaternary succession encountered in CRP-2/2A is divided into twelve recurrent lithofacies (some of which have been subdivided further), reflecting a range of marine, glacimarine and possibly subglacial environments of sediment accumulation. A cyclical vertical arrangement of lithofacies was noted throughout the core, and is used as the basis for a sequence stratigraphic analysis. Twenty-four sequences are recognised, each of which begins with a Sequence Boundary (Glacial Surface of Erosion), and each is interpreted to record a cycle of glacial advance and retreat with associated changes in relative sea-level. During at least some of these cycles, ice is interpreted to have extended as far as and seaward of the drill-site. A recent reinterpretation of seismic reflection data by Henrys et al. (this volume) permits the first correlation between seismic reflection records and the stratigraphic surfaces identified herein. All but one of the reflectors recognised correspond to sequence boundaries, and most reflectors correspond to the base of thin, truncated and amalgamated sequences. Additionally, three thick and relatively complete sequences (9 to 11) are identified individually by seismic reflectors. The major surfaces of omission in CRP-2/2A, identified from a variety of evidence, correspond to changes in cross-sectional geometry in the seismic records, and in the case of the unconformity at 307 mbsf can be interpreted as recording the onset of a phase of active tectonic subsidence associated with half-graben development, bounded by periods of more uniform, slower, possibly thermal subsidence. Possible controls on cyclicity are discussed, and include long-term eustatic cycles, Milankovitch frequency cycles, and more local climatic and/or tectonic events. The analysis allows the recognition and separation of tectonic from climatic (?glacio-eustatic) controls on the Cainozoic stratigraphy of the McMurdo Sound region

Composition and textural variability along the 10 m isobath, Great Barrier Reef: Evidence for pervasive northward sediment transport

Abstract: Previous workers have proposed that northward-directed bedload transport dominates the inner shelf of the Great Barrier Reef lagoon. Results from a sediment sampling survey along the 10 m isobath between Bowen and Cape York reveal a series of northward trends of increasing sediment maturity and demonstrate pervasive north-directed sediment transport interacting with a succession of sediment (fluvial) sources. South of the Tully River, the occurrence of limited compositional variability indicates significant mixing on the inner shelf. However, further north the data are highly variable, suggesting that sediment inputs from individual rivers may be retained relatively close to source. This may be related to a greater sediment trapping efficiency within northern embayments and/or by lower net rates of along-shelf transport.

Shelf sediments adjacent to the Herbert River delta, Great Barrier Reef, Australia*

Abstract: On the Great Barrier Reef shelf, terrigenous sediments adjacent to the Herbert River delta are strongly partitioned within the coastal zone, in common with the regional presence of a terrigenous inner-shelf sediment wedge. Partitioning is primarily controlled by wind-driven currents and waves associated with persistent southeast trade winds. Bottom-return currents provide the likely mechanism for episodic transport of fine-grained sediment in an offshore direction, although modelled bottom-return currents appear incapable of transporting much sediment seawards beyond the 20 m isobath. This depth corresponds to the observed outer limit of the nearshore sediment wedge

Spatial variability in fluvial style and likely responses to sea-level change, Herbert River, Queensland*

Abstract: In broad terms, fluvial systems can be considered as comprising two basic geomorphologic features, a channel and its floodplain (overbank), each of which may accumulate sediment or undergo erosion. The sedimentary relationships between channels and floodplains, the resultant sedimentary architecture and the form of the dependent landscape may all be considered in terms of the relative rates of channel and floodplain aggradation and/or erosion. Using this approach, the Herbert River in north Queensland can be divided into seven 'fluvial fields'. By considering the likely migration directions of field boundaries in the lower floodplain we conclude that, contrary to many sequence-stratigraphic models, lowering sea-level would drive a general aggradation of the system on the Great Barrier Reef shelf, whereas a sea-level rise would cause further incision of the modern coastal plain.

Laser-Derived, Particle Size Data from CRP-2/2A: Implications for Sequence and Seismic Stratigraphy

Abstract: Gravel-free, high-resolution (1-metre spacing, 32 channel) particle size data from the CRP-2/2A drill core indicate that many of the diamictites were likely deposited from floating ice. Textural dislocations occur at most sequence boundaries and provide independent corroboration of the sequence stratigraphic interpretation. Likewise the data largely support the correlation drawn (Fielding et al., this volume) between the sequence stratigraphic cycles and the regional seismic stratigraphy (an alternative correlation to Reflector ‘f’ is also suggested). The gravel-free data appear to be reflecting predominantly regional (global?) forcing with some possible local effects, and long-term trends persisting through gravelly textural dislocations.