Earthquake-controlled event deposits and its tectonic significance from the Middle Permian Wandrawandian Siltstone in th
The Sydney-Bowen basin in eastern Australia is an elongate back arc-converted foreland basin system situated between the Lachlan Fold Belt in the west and the New England Fold Belt in the east. The Middle Permian Wandrawandian Siltstone at Warden Head near Ulladulla in the southern Sydney Basin is dominated by fossiliferous siltstone and mudstone, with a large amount of dropstones and minor pebbly sandstone beds. Two general types of deposits are recognized from the siltstone unit in view of the timing and mechanism of formation. One is represented by the primary deposits from offshore to subtidal environments with abundant dropstones of glacial marine origin. The second type is distinguished by secondary, soft-sediment deformational deposits and structures, and comprises three layers of mudstone dykes of seismic origin. In the latter type, metre scale, laterally extensive syn-depositional slump deformation structures occur in the middle part of the Wandrawandian Siltstone. The deformation structures vary in morphology and pattern, including large-scale complex-type folds, flexural stratification, concave-up structures, faulting of small displacements accompanied by folding and brecciation. The slumps and associated syn-sedimentary structures are attributed to penecontemporaneous deformations of soft sediments (mostly silty mud) formed as a result of mass movement of unconsolidated and/or semi-consolidated substrate following an earthquake event. The occurrence of the earthquake event deposits supports the current view that the Sydney Basin was located in a back-arc setting near the New England magmatic arc on an active continental margin during the Middle Permian.
作 者： DU Yuansheng G. R. Shi GONG Yiming 作者单位： DU Yuansheng,GONG Yiming(Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China)G. R. Shi(Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China; School of Ecology and Environment, Deakin University, Victoria 3125, Australia)
刊 名： 中国科学D辑(英文版) SCI 英文刊名： SCIENCE IN CHINA (EARTH SCIENCES) 年，卷(期)： 2005 48(9) 分类号： P3 关键词： Permian seismites earthquake tectonics Sydney Basin Australia