The new Lake George core - Sutton Landcare meeting, Sutton

At 8.00pm, our guest speaker, Dr Bradley Opdyke, Senior Lecturer and Research Scientist, ANU Research School of Earth Sciences, will address us on the topic: "The new Lake George core: evidence for changing climate and uplift of the Lake George escarpment over the past 2 million years".

 

 

This is a follow up to Brad’s 2015 address to our group on how studying the history of Lake George can give us clues about our future climate in a warming world.

 

A core recovered from the middle of Lake George near Geary’s Gap records a detailed record of changing lake levels as well as the most recent interval that the Lake George basin was connected to the Yass River through Geary’s Gap.  The core is over 70 meters long and the record stretches back over 2 million years.

 

The sediments indicate the lake was relatively deep from 1 to 2 million years ago, then around 1 million years ago (the mid-Pleistocene transition), a river ran through it.  Presumably this indicates that the ‘Gap’ had eroded down to lake level and the Yass River captured this flow.  Shortly after this, the escarpment would have experienced significant uplift, cutting the basin off once again and allowing the water level to deepen once more. The last half a million years of core material contain abundant sedimentological and geochemical evidence of the periodic drying of the Lake George Basin, interspersed with much deeper water level intervals.

 

Brad is an expert in his field of paleoclimatology and a great communicator on the science of climate change. This update should be of particular interest to all those interested in this critical subject.