Biostratigraphic collections of Devonian fish fossils from Middle Devonian Aztec Siltstone at the top of the Taylor Group (Beacon Supergroup) and sediment studies for a basin analysis

Using toboggans and sledges, the party travelled 700 kilometres from the Darwin Glacier northwards to the Lashly Mountains to study Taylor Group sedimentary rocks (Beacon Supergroup). The principle objective of this expedition was to make detailed biostratigraphic collections of Devonian fossil fish from the Middle Devonian Aztec Siltstone at the top of the Taylor Group. A second objective was to document, where possible, the similarities or differences between the underlying arenaceous Taylor Group formations of the Darwin and Skelton Glacier areas to facilitate correlation and basin analysis. The Aztec Siltstone was measured at Gorgon's Head. Outcrops of Junction Sandstone (basal Taylor Group) and the overlying Hatherton Sandstone east of Gorgon's Head were also studied. From the mouth of the McCleary Glacier north to the Mulock Glacier, the geology of the Cook Mountains was investigated with the measurement of Aztec Siltstone exposures at several localities (Fault Bluff, Mount Gudmundson and the expedition-named sites Fish Hotel and Sliver Ridge) while older sediments were studied further east. After a helicopter crossing of the dangerous Mulock Glacier, sections were studied and measured on Mount Ritchie, Mount Kohn, Alligator Peak, the Warren and Boomerang Ranges, Swartz Nunataks and Escalade Peak, Sowee Ridge, Mount Metschel, Portal Mountain and Mount Crean in the Lashly Mountains. Four outcrops were measured for the first time. A total of 18 Taylor Group outcrops were studied in detail during the expedition. Many new specimens of fossil fish were found as well as extremely large Beaconites burrows in certain sandstones. A total of 750kg of rock was collected from 21 different sites.