The Stonewall Gap plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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Stonewall Gap’s center stands about 7,940 ft above sea level. Within three miles the land runs from 7,670 ft to 9,780 ft, a difference of 2,110 ft: mountain country. The highest named summit within 15 miles is Culebra Peak, about 13,980 ft, 8 miles west-southwest.
Under the town center the state geologic map shows Pierre Shale (Kp), Niobrara (Kn), and Carlile, Greenhorn, and Graneros (Kcg) Fms, undivided (shale, limestone), from the Early Cretaceous to Late Cretaceous, 66 to 145 million years old.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 3×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Arkose, siltstone, shale. Age: Late Cretaceous to Paleocene, 56 to 100 million years old. About 9 mi of the line.
Conglomerate, sandstone, siltstone. Age: Carboniferous to Permian, 252 to 324 million years old. About 5 mi of the line.
Granite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 3 mi of the line.
Conglomerate, sandstone, shale. Age: Paleocene, 56 to 66 million years old. About 2 mi of the line.
Shale, limestone. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 2 mi of the line.
Gneiss. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 5 smaller units along the line are not listed.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Stonewall Gap reaches the Gulf of America by way of the Purgatoire, the Arkansas and the Mississippi: about 1,940 river miles.
Lakes on the way: Murray Lake and Ozark Lake.
850 miles of the trip are on the Arkansas.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Stonewall Gap; river miles along the main stem, rounded.
