Geochemical evidence from Lower Permian volcanic rocks of northeast New South Wales for asthenospheric upwelling following slab breakoff |
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| Authors: | G Caprarelli E C Leitch |
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| Institution: | Department of Environmental Sciences , University of Technology , PO Box 123, Broadway, Sydney, NSW, 2007, Australia |
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| Abstract: | Within the Daly River basin, Northern Territory, three erosion surfaces are described and their relationships to deep weathering are discussed. The Bradshaw surface is the highest and oldest surface recognized. It is of considerable perfection and forms main divides; it is associated with a deep lateritic profile with a strongly silicified horizon forming the lower part of the pallid zone and extending into rocks immediately beneath. The Maranboy surface now forms secondary divides, with related rock‐cut terraces, below the level of the Bradshaw surface. In most areas it was produced by the stripping of the upper, less silicified parts of the Bradshaw pallid zone. The Maranboy surface is associated with a lateritic weathering profile less deep than the Bradshaw profile and mainly developed in the Bradshaw weathering mantle. A younger erosion surface, the Tipperary surface, advanced by the removal of the Maranboy re‐weathered layer exposing the resistant Bradshaw silicified rock which commonly forms a base‐level of denudation. The Tipperary surface consists of broad plains, gently undulating terrain, and dissected headwater valley floors. It is relatively unweathered and carries depositional mantles which are attributed to climatically induced slope instability. The ages of the erosion surfaces and the possibility of climatic changes in the area are also briefly discussed. |
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| Keywords: | asthenosphere basalt geochemistry geodynamics New England Fold Belt Permian |
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