Holocene glacial history of College Fjord, south-central Alaska

Abstract

Holocene glacier fluctuations in College Fjord in south-central Alaska provide an integrated proxy record of climatic and related environmental changes through this critical geologic epoch. During the early Holocene around 10,000 yr BP, ice was receding from lower Port Wells but was still present in College Fjord. With the beginning of the Holocene Climatic Optimum, recession increased and the ice front reached the Golden Moraine site 1 by 7680 cal yr BP, starting its long early to middle Holocene retreat to the head of tidewater. An ice-free fjord existed between 7680 cal yr BP and about 5190 yr BP. A middle Holocene advance started between approximately 5190 and 4470 yr BP with ice arriving at the mouth of the fjord before 2470 cal yr BP. The late Holocene was characterized by various standstills and minor readvance positions as the glacier fell back and by significant Little Ice Age expansions and retreats of individual glaciers present in the fjord. During the late Holocene, the glacier built four large and distinctive moraines all representative of at least four standstill positions of College Fjord Glacier before 2470, 2060, 1330, and approximately 1120 cal yr BP.