University of Tasmania

File(s) under permanent embargo

Evidence of Proterozoic primary CaC03 precipitation from the McArthur Group of northern Australia

conference contribution
posted on 2023-05-26, 08:32 authored by Winefield, PR, Peter McGoldrickPeter McGoldrick
ABSTRACT: Radiating fans of acicular 'Coxco needles' are the characteristic feature of the Coxco Dolomite Member , a subunit of the Teena Dolomite within the Palaeoproterozoic McArthur Group. In the past, 'Coxco needles' have been variably interpreted as dolomitic pseudomorphs after aragonite, gypsum or trona. More recently, gypsum and an emergent brine pool depositional setting has been the favoured interpretation. New work reported here has found that crystal morphology, geochemistry, petrographical and sedimentological relationships are more consistent with a subaqueously deposited aragonitic precursor. The widespread occurrence of 'Coxco needles' at a confined stratigraphic interval is thought to be a function of a subtle change in the HC03 concentration within the water body during deposition of the Teena Dolomite. Although elevated atmospheric CO2 during the Proterozoic supports increased carbonate precipitation (including aragonitic fans), it can not satisfactorily explain the apparently synchronous precipitation of Coxco fans. Therefore, changes in the bathymetry of the McArthur Basin coincident with deposition of a broadly transgressive sequence is inferred to have triggered the widespread chronostratigraphic precipitation of carbonate (i.e aragonite tans) within a variety of lithofacies.


Publication status

  • Published

Event title

Proceedings of the 9th International Symposium on Water-Rock Interaction

Event Venue

Taupo, New Zealand

Date of Event (Start Date)


Date of Event (End Date)


Rights statement

Conference as a result of authors research for PhD thesis. Thesis title - Sedimentology and diagenesis of late palaeoproterozoic carbonates, Southern McArthur Basin, northern Australia. PhD thesis, University of Tasmania. Held at

Repository Status

  • Restricted

Usage metrics

    University Of Tasmania


    No categories selected


    Ref. manager