The Namatjira Formation, a mixed carbonate and clastic, Late Proterozoic‐Early Cambrian sequence, Amadeus Basin, central Australia

Abstract

The Namatjira Formation is a newly recognized mixed carbonate and clastic sequence from the eastern Gardiner Range in the Amadeus Basin, central Australia. The formation grades from clastic at the base to carbonate at the top, and contains three distinct lithofacies. Numerous small cycles, 1–5 m thick, are of tempestite origin. Detailed sedimentological and facies analysis indicates that the Namatjira Formation was deposited in a tidal flat to coastal lagoon environment, with periods of emergence and hypersalinity. The formation interfingers with, and is time equivalent to, the Arumbera Sandstone, which in the Gardiner Range has previously been assigned a Proterozoic age. This interpretation is now in question as the Namatjira Formation contains abundant vertical burrows and horizontal tracks, which in the Arumbera Sandstone elsewhere in the basin have been used to assign that unit to the Early Cambrian.