Title:Northern Black Hills Igneous Intrusions – USGS Lithograph Map of Dikes & Laccoliths, 1901. Style: 19th-Century Geological Map – Dikes, Sills, Laccoliths & Fault Structures in South Dakota. • Full title: “Map Showing Distribution of Dikes, Sills and Laccoliths, Northern Black Hills, South Dakota”.
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