BOLLA BOLLANA BOULDER BEDS by Peter Briggs
Glaciogenic deposits are common, often seen as unconsolidated moraines, tilled up sediments and deep clay deposits, but when Walter Howchin in 1907 saw solid rocks in Sturt Gorge he realised these were ancient glacial deposits and so began the study of Glaciogenic Geology. He brought a worldwide conference to Adelaide to further this study and soon similar ancient deposits were found around the world. Douglas Mawson then found extensive Diamictite deposits in the Flinders Ranges, again of glaciogenic origin. In the Gammon Ranges-Arkaroola region, we have some of the largest preserve glaciogenic deposits in the world, formed in the Cryogenian when the Earth was in near ‘Snowball Earth’ conditions for 57 Ma. The Bollana Boulder beds are the equivalent of the Sturt Tillite and part of the Sturtian Period, a name given to represent this period worldwide. On our doorsteps we have a world class example of this freezing time in Earths history, something we will see on our soon Arkaroola Field trip.
