Determining the origin of the Mawson Diamictite in the Coombs Hills, Carapace Nunatuk Region

The Mawson Diamictite of the Coombs Hills was visited to compare the succession with that of Carapace Nunatak 10 km to the west. At Carapace Nunatak a pronounced ridge of hyaloclastite with fossiliferous sediment at its base had been studied the previous year to determine the relationship between the pillow lava at its base and the underlying lake sediment. Two diamictites, with associated water-lain sands and silts, were found interbedded with the lava sequence, one of which is partially preserved in a down faulted block. At Coombs Hills more extensive outcrops allowed a detailed study to be made of the diamictite and its components. The upper part of the sequence, which overlay the diamictoite and formed the top of Mt Brookes, was found to be composed of thick subaerial lavas. A ridge on the NE side was climbed, measured and samples taken of individual lava flows.