Core sample dating
The sediment of Lake St Anne was sampled several times already, but never reached the bottom of the lake before.During the winter of 2013 at a new core location drilling started at 600 cm water depth and finally reached the bottom of the lake sediment at approximately 2300 cm including water depth.At the root of their quest is a climate transition that marine-sediment studies reveal happened some 1.2 million years to 900,000 years ago."The Mid Pleistocene Transition is a most important and enigmatic time interval in the more recent climate history of our planet," says Fischer.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.Furthermore the late part of the sediment section (between 15,000 and 30,000 cal.yr BP) has low organic matter content (less than 2-4%) with scarcity of datable plant macrofossil material.This type of organic material could be an ideal candidate for radiocarbon based chronological studies as it has terrestrial source and is present in the whole core in contrast with the terrestrial macrofossils.Although the pollen remains were present in the whole core, in many cases their amount give a challenge even for the AMS technic.
"The reason for this change is not known." Climate scientists suspect greenhouse gases played a role in forcing this transition, but they need to drill into the ice to confirm their suspicions.