Map 7: Structure Contours of the Top of the Ordovician Trenton Limestone (or Equivalent)
This map shows the variation in elevation of the top of the Trenton Limestone, a unit deposited near the end of the Ordovician. The Trenton is the deepest sedimentary unit contoured. Its elevation clearly shows the shape of the Illinois Basin, the Rough Creek Graben, and the Cincinnati Arch. The color of this map coincides with the color of the Ordovician Stage rocks depicted on the Bedrock Geology with Bedrock Topography map (Map 4).
[{'id': 27, 'name': 'Contour labels'}, {'id': 29, 'name': 'Contours'}, {'id': 30, 'name': 'Shaded relief'}, {'id': 31, 'name': 'Elevation'}]
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