Diagenetic history of Triassic sandstone from the Beacon Supergroup in central Victoria Land, Antarctica

Abstract

The diagenetic history of Triassic sandstone from the Beacon Supergroup, Victoria Land, Antarctica, can be divided into three main phases of shallow burial diagenesis, contact diagenesis (temperatures of 200–300°C), and post‐contact diagenesis, on the basis of petrographic and geochemical analyses. Shallow burial diagenesis is characterised by minor compaction, K‐feldspar alteration to illite, and quartz cementation. Contact diagenesis is related to emplacement of dolerite intrusions and basalt flows during Gondwana break‐up at 180 Ma. This high‐temperature diagenetic phase is dominated by zeolite cementation, even in sandstone poor in zeolite precursor materials. Elevated thermal conditions associated with the igneous intrusions are suggested by increased illite crystallinity, but strong evidence for contact metamorphism is missing. Post‐contact diagenesis is signified by zeolite and K‐feldspar dissolution, and local quartz, calcite cementation, and minor albite and K‐feldspar precipitation. This diagenetic phase is possibly related to renewed (hydro‐) thermal activity in Victoria Land in association with rifting of New Zealand and Australia from Antarctica at c. 96 Ma.