Interpretation of lithofacies of the Ashtabula Till along the south shore of Lake Erie, northeastern Ohio

Abstract

The final advance of the Erie lobe into Ohio during the Port Bruce Stade of the Late Wisconsinan deposited the Ashtabula Till. Wave erosion and mass wasting along the south shore of Lake Erie show that the Ashtabula Till consists of laterally traceable lithofacies, which are used to determine the depositional history of the Ashtabula Till. At each section, lithofacies sequences are divided into two sub-sequences, each consisting of massive, matrix-supported diamicton (Dmm) overlain by stratified, matrix-supported diamicton (Dms). Some Dmm are sheared (Dmm(s)) and are interpreted as lodgement till, whereas other Dmm and Dms were deposited as melt-out till. Some sections contain lenses of fines (Fm and Fl), current-reworked diamictons (Dmm(c) and Dms(c)), and resedimented diamictons (Dmm(r) and Dms(r)). The two sub-sequences represent two advances of Ashtabula ice that deposited the Euclid and Painesville moraines about a kilometre apart. During and after recession of the Ashtabula ice, waves and currents in Lake Maumee and its successors reworked outwash and diamictons to form the lake plain. The texture of Dmm(s) is significantly different from that of most other diamictons, and Dmm has the smallest carbonate content of all diamictons. Analysis of the variations in texture and composition among lithofacies provides additional evidence of the effectiveness of lithofacies logging in interpretation of glacial processes.