Abstract

The Eregunda Sandstone Member (Middle Cambrian) of the Billy Creek Formation crops out sporadically in the Flinders Ranges of South Australia. The member comprises two major lithofacies (sandstone and shale/siltstone) which are closely associated and commonly laterally equivalent. The fine-grained lithofacies contains marine trace fossils, desiccation cracks and halite casts, and is characterised by poorly developed tidal-type stratification. A low energy intertidal to shallow subtidal origin is envisaged. The sandstone lithofacies is dominated by current-laid sandstones, commonly arranged in waning-current cycles typical of braided-channel flood deposits. Marine trace fossils are very uncommon in these units, although their abundance increases towards the north and northwest, where the sand units are thin and relatively distal with respect to the terrigenous source area. The intimate association of tidal mudflat deposits and current-laid sandstones indicates that the Eregunda Sandstone Member was deposited in a shoreline environment, probably as a complex of interlocking, fluvial-dominated deltas which built out into a shallow epicontinental sea.

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