Date of Award

2008

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

George H. Denton

Second Committee Member

Peter Koons

Third Committee Member

Joerg Schaefer

Abstract

Milankovitch Theory explains the basic link between variations in earth’s orbital parameters and the occurrence of ice ages. By this hypothesis, glaciers in the at different latitudes respond to different insolation signals, which are out of phase between the Northern and Southern Hemispheres because they are precession-dominated. However, existing moraine chronologies indicate that glaciers in the middle-latitude Southern Hemisphere may be in-sync with those in the Northern Hemisphere (Mercer, 1984). To provide a basis for understanding what drives glaciations in southern middle latitudes I developed a 10Be exposure-age chronology for Last Glacial Maximum (LGM) moraines in the Pukaki Basin, New Zealand. Results show that the regional glacial maxima were achieved at ~35,000, 27,000, 25,000, 20,000, 19,000 and 18,200 years ago. Moraines distal to the LGM sequence yield an age range of 60,300 ± 1,400 to 69,300 ± 1,600 years ago. The precision of these exposure ages allows for detailed comparisons with climate records from Northern Hemisphere and Southern Hemisphere middle latitudes as well as with insolation curves. This chronology allows me to test several hypotheses about the predicted timing of ice maxima and whether the theories are supported, rejected, or in need of revision. The maxima occur during both local summer intensity insolation maxima and minima, suggesting that overhead insolation is not the only factor controlling glacier mass balance.

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