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abstracts
Extracting moraine ages from statistical distributions of cosmogenic exposure dates (YSM POSTER PRIZE)
Patrick Applegate, Richard Alley
Moraines are distinctive landforms that mark the past extents of glaciers, which are sensitive to climate change. The ages of these landforms can be determined using cosmogenic exposure dating. However, the statistical distributions of exposure dates from moraines commonly show more scatter than can be explained by the measurement error of the technique. Here, we present models of two geomorphic processes that may influence the statistical distributions of cosmogenic exposure dates on moraines. These processes are moraine degradation and inheritance due to boulder reworking or landsliding onto glacier surfaces. We generate synthetic statistical distributions of exposure dates from these models using Monte Carlo methods. We fit the models to collections of exposure dates from real moraines by matching the cumulative density functions of the modeled and observed distributions. This process yields improved estimates of the ages of the moraines. We present fits of the model to real data sets from moraines whose ages are important in paleoclimate, and discuss the implications of the differences between the ages yielded by our interpretive methods and other possible age estimates.
Patrick Applegate, Department of Geosciences, Pennsylvania State University,503 Deike Bldg. , University Park, PA 16802, United States, papplega@geosc.psu.edu
Richard Alley, Pennsylvania State University, Department of Geosciences, University Park, PA 16802, United States
Session: CCT1: Chronology
Download Poster:
> PAGES_YSM09_Applegate.pdf
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