| Summary: | The Sydney Basin covers an area of approximately 52000 km2 and is located around the city of Sydney in New South Wales, Australia. About 70% of the basin is onshore and the rest underlies the narrow continental shelf offshore. The Permian and Triassic strata that fill the basin provide an ideal opportunity to better understand the interplay of various allogenic controls during deposition of coastal to shallow marine strata. The early-middle Permian strata were deposited during a rift-sag phase whereas the later Permian and Triassic strata accumulated in a foreland basin related to the New England Fold Belt. During deposition of the strata, the world experienced a major transformation from icehouse conditions in the early Permian to greenhouse conditions in the Early Triassic. Observations and interpretations, based on a study of outcrops, well logs and cores, were made to provide new insights on the evolution of depositional systems, changes in climatic regimes, and the role of tectonism during evolution of the Sydney Basin. To this end, a series of regional cross-sections and paleogeographic maps were prepared. There is abundant evidence of cold climate conditions in the early Permian (Cisuralian) strata of the Sydney Basin. The basal formation in the southern part of the basin, the Wasp Head Formation, has abundant evidence of glacial activity including facies interpreted as tillites and glacial outwash. Large en echelon blocks are interpreted as glaciotectonic push moraines. Dropstones and glendonites are common in the Cisuralian sediments indicating cold marine waters with floating ice. Small ice-keel scours seen within shallow marine sediments also indicate the presence of at least seasonal floating sea ice. The abundance of dropstones appears to be more a function of sedimentation rates (more dropstones in sediments that accumulated slowly) than a function of the variations in floating sea ice over time. Most of the Cisuralian strata consist of shoreface-offshore facies with some estuarine deposits. The ...
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