Title: Siliciclastic Braided‐Alluvial Sediments Intercalated within Continental Flood Basalts in the Early to Middle Proterozoic Mount Isa Inlier, Australia
Abstract: The Eastern Creek Volcanics in the Mount Isa Inlier are up to 7 km thick and consist of two successions of subaerial basalts (5.5 km and 0.7 km thick) separated by a siliciclastic unit (up to 750 m thick). Predominantly tabular, siliciclastic units from 1 to 40 m thick are present in the upper half of the lowermost basaltic succession and throughout the uppermost basaltic succession. Siliciclastic debris was derived exclusively from the east from a provenance terrain consisting of quartz arenites, felsic volcanics and granites. With the exception of local aeolian facies, the siliciclastic units are exclusively of braided-alluvial origin. Facies analysis has identified two interacting alluvial systems: a relatively high-gradient and coarse-grained, transverse system that supplied siliciclastic debris from eastern highlands, and a lower-gradient and finer-grained, longitudinal or trunk system that reworked sediment down a south-to-north palaeoslope. Areal persistence of most siliciclastic units in the trunk system is attributed to continuous lateral switching of shallow, braided rivers. Lateral switching was promoted by slow subsidence attributed to cooling and thermal contraction of the volcanics. Siliciclastic units define prolonged hiatuses in volcanism; this interpretation is supported by the presence of a calcrete unit at the top of a basalt flow and below a siliciclastic unit.
Publication Year: 1993
Publication Date: 1993-09-16
Language: en
Type: other
Indexed In: ['crossref']
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Cited By Count: 18
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