Abundant pseudomorphs and relicts of gypsum, anhydrite, and halite occur in the Mallapunyah Formation and Amelia Dolomite of the Proterozoic McArthur Group of the Northern Territory. The rocks have undergone a complex history, in which several stages can be detected. These are: (a) They were deposited in a regressive/transgressive cycle with frequent minor oscillations. The sedimentary sequence shows a striking resemblance to the Pleistocene and Holocene sediments of the Abu Dhabi sabkha. (b) The evaporites were emplaced diagenetically after formation of black chert and early dolomite. Deposits in the McArthur Group sections can be closely compared with the early diagenetic facies zones of Abu Dhabi. By analogy with the Holocene the positions of particular evaporite parageneses can be located within the palaeo-sabkha. (c) Textures indicating dehydration of gypsum to anhydrite and vice versa can be detected, but the sulphate evaporites, and some of the halite, have been replaced by ferroan carbonate during burial diagenesis, at a depth of burial estimated at over 1 km. Sulphate-rich brines which also contained high metal concentrations were released at this time, and made their way through a number of accessways to overlying formations. These brines provided, at least in part, a source of sulphate and of metals for mineralisation in the Emmerugga Dolomite and Barney Creek Formation. (d) Later vadose and phreatic activity resulted in minor copper mineralisation, and in cementation and recrystallisation of the carbonates. Silcrete and magnesite-rich crusts are common on beds of replaced evaporite minerals. (e) The presence of an arid Abu Dhabi-like sabkha indicated the prevalence of a particular climatic regime. If these same climatic conditions can be identified in northwest Queensland, there exists the possibility for climatic stratigraphic correlation at an intermediate level between radiometric, and micropalaeontological and magneto-stratigraphic correlation.
