Paleoenvironmental reconstruction of the Last Glacial Maximum, inferred from insect fossils from a tephra buried soil at Tempest Lake, Seward Peninsula, Alaska

Abstract

Sediments and vegetation dated 21,570 cal yr BP were buried under tephra on the northern Seward Peninsula. This buried surface has yielded plant macrofossils in growth position, as well as numerous insect fossils, excellently preserved in permafrost. It appears that many of the insects were buried alive by the volcanic ash. The species composition and ecological affinities of this fossil fauna are typical of Alaskan Late Pleistocene steppe–tundra environments. The assemblages are dominated by the weevil Lepidophorus lineaticollis, one of the most common species in Eastern Beringian Pleistocene fossil assemblages. Many other members of the ancient steppe–tundra insect community are preserved in these assemblages, including the pill beetle Morychus sp. and weevils of the genus Coniocleonus. In Alaska, most of these species (but not all of them) survived the Pleistocene/Holocene environmental transition, but are restricted today to relict patches of steppe-like vegetation. Faunal diversity is low, in spite of the recovery of more than 1000 individual insects and mites including more than 600 beetles. This reflects the small number of species adapted to the cold, dry environments of the LGM in Eastern Beringia. They represent an ecosystem which no longer exists.