Stratigraphy and Structure of the Southern Myally Block, Mount Isa Inlier, Queensland.

The oldest sedimentary unit exposed on the southern Myally Block is the 1050m thick Quilalar Formation, which overlies the Kalkadoon Granite and Leichhardt Volcanics. Deposition was in a marine environment. Sea-level variations were responsible for alternating periods of shelf and shoreface conditions during deposition or the lower portion. A decrease in siltstone and an increase in sandy and stromatolitic carbonate in the upper portion represents the establishment of shallower marine or lagoonal conditions. These conditions are laterally extensive, and the formation has therefore been interpreted as a sagphase sequence, deposited after a period of crustal extension. […]