GLACIAL SEDIMENT AND LANDFORM MAPPING ON THE DELTA, OH 7.5' TOPOGRAPHIC MAP

A 7.5’ series surficial map of the Delta Quadrangle is based on a LiDAR DEM using a sediment landform approach to evaluate the glacial history near Delta, Ohio. Water well logs to bedrock provided deeper stratigraphic data, while hand augers and geophysical surveys provided more detail on the most recently deposited sediments; the focus of this study. Overlying bedrock is a basal unit of sand and gravel. It is overlain by a basal diamicton reaching thicknesses > 50 m in the northwest map corner and thins to 14 m thickness in the southeast. The thickness change corresponds to the elevation change across the same area. Overlaying and cut into the basal diamicton are six surficial map units. (1) Hummocky terrain: defined by low relief, irregular, and circular shaped hillocks in the northwest with particle sizes ranging from clayey-silt to cobbles. (2) Hummocky ridge: a relatively high relief, discontinuous, NE-SW trending ridge of most likely a littoral origin that borders the southeast edge of the hummocky terrain. This ridge was formally mapped as the Lake Maumee II shoreline and consists of particles ranging from silt to gravel. (3) Glacial lacustrine plain: the central portion of the map is a broad lake plain capped by younger sand dunes and arcuate sand and gravel ridges of uncertain origin. (4) Glacial lacustrine ridge: A well-defined ridge with spits composed of sand and gravel previously mapped as the Whittlesey shoreline. (5) Till plain: to the southeast is a broad plain in which diamicton is commonly exposed at the surface even though glacial shorelines lie above and below it. (6) Abandoned stream network: an extensive, well-defined network of channels border the southeastern edge of the map sheet. While the hummocky ridge (2) is formally mapped as the Lake Maumee II shoreline it associates with a weakly developed channel paralleling it on its eastern side. Hummocky characteristics suggest a formation in an ice-contact environment unlike the lower Whittlesey shoreline. This map provides greater detail on the processes and timing of events during deglaciation.