Surface exposure dating
The implication is that climate during the Last Glacial Maximum was generally synchronous at the global scale.
However, the late-glacial readvance to 95% of the extent of the largest advance during the Last Glacial Maximum at 14.4±0.9 ka is distinctively “Antarctic” in nature.
We use these tools to interpret 49 Al surface exposure ages of erratic boulders on six last-glacial and late-glacial moraines at Lago Buenos Aires, Argentina (LBA; 71°W, 46.5°S).
Seven of the 49 boulders are identified as anomalously young, and are interpreted to have been exhumed after moraine deposition.
We use the mean square of weighted deviates (MSWD) statistic and cumulative frequency plots to identify groups of boulders that have statistically similar ages based on the number of analyses and their uncertainties.
These samples most likely represent the true age of the moraine.
This long period of applicability is an added advantage of cosmogenic nuclide dating.
Dating of erratic boulders and adjacent ice-sculpted bedrock on the island of Bornholm in the western Baltic Sea reveals almost identical values.
It was discovered about a decade ago that cosmic ray interaction with silica and oxygen in quartz produced measurable amounts of the isotopes Beryllium-10 and Aluminium-26.
Researchers suggested that the accumulation of these isotopes within a rock surface could be used to establish how long that surface was exposed to the atmosphere.
In situ cosmogenic nuclides have become a powerful means to determine surface exposure ages of boulders on moraines and other landforms that are important to paleoclimate reconstructions.
Potentially the largest and least quantifiable source of uncertainty of these surface exposure ages is the variable exposure histories of individual boulders.