Late Pleistocene and Holocene glaciation of the Fish Lake valley, northeastern Alaska Range, Alaska

摘要

We reconstructed a chronology of glaciation spanning from the Late Pleistocene through the late Holocene for Fish Lake valley in the north-eastern Alaska Range using Be-10 surface exposure dating and lichenometry. After it attained its maximum late Wisconsin extent, the Fish Lake valley glacier began to retreat ca. 16.5 ka, and then experienced a readvance or standstill at 11.6 +/- 0.3 ka. Evidence of the earliest Holocene glacial activity in the valley is a moraine immediately in front of Little Ice Age (LIA) moraines and is dated to 3.3-3.0 ka. A subsequent advance culminated at ca. AD 610-900 and several LIA moraine crests date to AD 1290, 1640, 1860 and 1910. Our results indicate that Be-10 dating from high-elevation sites can be used to help constrain late Holocene glacial histories in Alaska, even when other dating techniques are unavailable. Close agreement between Be-10 and lichenometric ages reveal that Be-10 ages on late Holocene moraines may be as accurate as other dating methods.