China Bowl Cave: An Early-Middle Holocene non-analog faunule from Grand Rapids, central Manitoba, Canada

摘要

China Bowl, a small vadose cave in the northern Interlake Region of Manitoba, Canada (53 + degrees N, 99 + degrees W), yielded the first recorded cave assemblage from central Manitoba-an Early-Middle Holocene vertebrate faunule dating to 7715 rcy BP (8500 cal y BP). The faunule, comprising mainly small mammals and amphibians, suggests an open taiga punctuated by mixed groves of trees on drier uplands interspersed with low-lying wetlands in an area occupied only a few centuries previously by proglacial Lake Agassiz. Identified elements include 3368 teeth derived from 17 small mammalian species, most of which are today locally sympatric taxa. This late, non-analog fauna, which includes Bison sp. indet., also features collared lemming (Dicrostonyx, perhaps D. richardsoni) which is now disjunct from the China Bowl locality by some 400-500 km to the north. The early postglacial, post-Agassiz occurrence of Dicrostonyx in the northern Interlake supports hypotheses about (Richardson's?) collared lemming still recolonizing northward from a refugium south of the late-Wisconsin Glacial Maximum (LGM) limits as ice and Lake Agassiz shorelines retreated. More than 3800 amphibian bones were also recovered, along with a few snake and fewer avian remains.