Date of Award

8-2014

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

George H. Denton

Second Committee Member

Brenda L. Hall

Third Committee Member

Joerg M. Schaefer

Abstract

Here I test a working hypothesis that, in Southern Hemisphere middle latitudes, recession of mountain glaciers occurred during Northern Hemisphere Heinrich stadials, and glacier expansion occurred during Heinrich interstadials. As a blind independent test of this hypothesis, I produced a chronology of left-lateral moraines constructed by the Pukaki glacier in the Southern Alps of New Zealand. Using geomorphic mapping and 10Be surface-exposure dating, I show that five left-lateral moraine belts were formed during maxima of the last ice age. These belts afford ages of 43,347 ± 1502; 36,242 ± 1303; 26,6579 ± 1025; 19,917 ± 648; and 17,900 ± 391 yrs. These five maxima spanned an entire cycle of orbital variations in summer insolation intensity at the latitude of the Southern Alps (44°S). Thus the moraine chronology indicates that variations in the extent of the Pukaki glacier were not tied directly to overhead summer insolation intensity. Instead, the chronology shows that millennial-scale oscillations of the Pukaki glacier followed the pulsebeat of North Atlantic Heinrich stadials, superimposed on longer orbital frequencies. The 10Be surface-exposure moraine chronology supports the notion that shifting atmospheric circulation bands and Southern Ocean fronts provide the mechanism for this Heinrich teleconnection between the Northern and Southern Hemispheres. In addition, the moraine chronology affords evidence for massive glacial retreat early in the last ice-age termination, coeval with the onset of Heinrich stadial 1 in the Northern Hemisphere. Millennial-scale fluctuations with a Heinrich pulsebeat also characterized the Ohau glacier in the Southern Alps of New Zealand and the middle- latitude Andean ice lobes in the Chilean Lake District of South America.

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