Ldeo cosmogenic dating group
The CRONUS-Earth project sampled wave-polished bedrock and boulders on an extensive wave-cut bench formed during the Bonneville-level highstand that was abandoned almost instantaneously during the Bonneville flood.
CRONUS-Earth also sampled the Tabernacle Hill basalt flow that erupted into Lake Bonneville soon after its stabilization at the Provo level, following the flood.
Given the excellent agreement between the two age groups, we calculate a mean age of 14.8 /- 0.4 Be-10 ka for final deposition of the Pomeranian Moraine of northern Poland.
The age of the Pomeranian Moraine suggests that the southern margin of the SIS was near its maximum extent in Poland at a younger time than previously inferred, and that retreat from the moraine at 14.8 /- 0.4 Be-10 ka probably occurred in response to the onset of the Bolling interstade.
During the last ice age, glaciers dominated New Zealand’s Southern Alps until warming temperatures some 20,000 years ago sent them into retreat.
Scientists at Lamont-Doherty Earth Observatory, with their colleagues, are investigating the rocky remnants these glaciers left behind to learn precisely when the ice withdrew, and what glacier retreats globally can tell us about the climate system.
On the distribution of C-14 and Ar-39 in the Arctic Ocean: implications for deep water formation.
In the lab at Lamont, geochemist Michael Kaplan and lab manager Roseanne Schwartz are shown cutting the rock samples and isolating atoms of Beryllium-10 in a long chain of steps.
“We start with kilograms of rocks, take a hundred grams of quartz out and [are left] a few ten-thousandths of Beryllium-10,” says Schaefer.
These cosmogenic nuclides are monitors of exposure of the sample to open sky (and to bombardment of the sample surface by cosmic ray particles -neutrons and myons- that produce characteristic isotopes in the surfaces).
These techniques have advanced our abilities to quantify earth surface processes in general, and are particularly powerful in the field of glacier and ice-sheet dynamics and their coupling to climate change.