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 Wandr...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 Ulla-dulla 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 rep-resented by the primary deposits from offshore to subtidal environments with abundant drop-stones 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 un-consolidated 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.展开更多
Typical contourite deposits associated with submarine turbidite fan deposits are recognized for the first time from the Lower Devonian Liptrap Formation at Cape Liatrap, Victoria in southeast Australia. The contourite...Typical contourite deposits associated with submarine turbidite fan deposits are recognized for the first time from the Lower Devonian Liptrap Formation at Cape Liatrap, Victoria in southeast Australia. The contourites are well integrated within the turbidite fan deposits and are characterized by thin (5-8 cm), lenticular, well-sorted coarse-grained siltstones to fine-grained sandstones with current-ripples and cross beddings. The palaeocurrent directions of the turbidite fan and contourites are perpendicular to each other, with the former directed generally westward while the latter varying from 165° to 190° southward. In view of the facies types and architecture, we suggest that the turbidite fan was developed at the base of a westward inclined palaeo-slope, at the front of which the contourites were deposited as a result of southward flowing deep-sea contour (geostrophic) currents. The depositional setting inter- preted for the Liptrap Formation thus may provide a provisional model for the Lower Devonian conti- nental slope and abyssal basin environment in the southeastern part of the Melbourne Trough.展开更多
基金sponsored by the Australian Research Council(to G.R.Sh)the National Natural Science Foundation of China(to DU,No.40372061)
文摘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 Ulla-dulla 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 rep-resented by the primary deposits from offshore to subtidal environments with abundant drop-stones 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 un-consolidated 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.
基金the National Natural Science Foundation of China (Grant Nos. 40672080, 40621002)the Ministry of Education of China (Grant No. IRT0546)the Australian Research Council (Grant No. DP0772161 to GRS)
文摘Typical contourite deposits associated with submarine turbidite fan deposits are recognized for the first time from the Lower Devonian Liptrap Formation at Cape Liatrap, Victoria in southeast Australia. The contourites are well integrated within the turbidite fan deposits and are characterized by thin (5-8 cm), lenticular, well-sorted coarse-grained siltstones to fine-grained sandstones with current-ripples and cross beddings. The palaeocurrent directions of the turbidite fan and contourites are perpendicular to each other, with the former directed generally westward while the latter varying from 165° to 190° southward. In view of the facies types and architecture, we suggest that the turbidite fan was developed at the base of a westward inclined palaeo-slope, at the front of which the contourites were deposited as a result of southward flowing deep-sea contour (geostrophic) currents. The depositional setting inter- preted for the Liptrap Formation thus may provide a provisional model for the Lower Devonian conti- nental slope and abyssal basin environment in the southeastern part of the Melbourne Trough.
