25 All Things Aeolian

Tuesday, 19 May 2020
8:00 AM - 12:00 PM
French River Room 1

AEOLIAN GEOMORPHOLOGY AND GEOARCHEOLOGY OF THE KIWANIS SITE, CHIPPEWA RIVER VALLEY, WISCONSIN

Paper number: 25-3
Program: Theme Sessions
Time: 8:40 AM – 9:00 AM

Authors

Abstract

Recent research revealed the presence of aeolian cliff-top dunes (CTD) in the lower Chippewa River valley (LCRV) of west-central Wisconsin, USA. These CTDs are hypothesized to result from the exposure of alluvial sediments as the Chippewa River incises into alluvial fill. Wind entrains exposed sediments and transports them over terrace escarpments where they are deposited. Orientation of parabolic morphology in proximity to terrace scarps and sedimentary structures within CTDs support this hypothesis. Prominent (up to 23m in height) and morphologically distinct CTDs were investigated at the Kiwanis site to understand the geomorphology and chronology of deposition. Optical stimulated luminescence (OSL) ages indicate two phases of deposition, ~910 yr and 560 yr. LiDAR DEM analysis also revealed three conical mound-like forms (~1.25 - 2.5m tall, ~7 - 17m in diameter) enclosed by two linear ridges (~1.2m tall, 125m long). Their spatial arrangement and more subtle, non-parabolic morphology suggest an anthropogenic origin. In consultation with local Native American tribes, geophysical techniques were used to characterize their internal structure to test our hypothesis. Analysis of ground penetrating radar (GPR) results proved inconclusive and require more data to interpret reflection facies. Electrical resistivity (ER) and magnetometry (MT) data indicate the conical mounds are likely composed of altered material unlike the adjacent aeolian landscape. Thus, we interpret this site to represent a coupled anthro-aeolian system. The shape, size, and configuration of these forms are consistent with patterns observed in the Effigy Mound ritual complex (~1,320 – 820 yr) in the region. The site layout compares favorably with contemporaneous and later petroglyphic, pictographic, and pottery and textile decoration representations of a spirit being named Thunderer, an upperworld being representing sky-related phenomena such as storms and wind. Future OSL dating of the mounds will allow for comparison of ages with the CTDs. If verified, this would represent exceptionally rare and important evidence of ancient Native peoples responding to natural phenomenon by creating a physically integrated symbolic landscape.

Geological Society of America Abstracts with Programs. Vol. 52, No. 5

doi: 10.1130/abs/2020NC-347758

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