The Allendale 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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Allendale’s center stands about 190 ft above sea level. Within three miles the land runs from 140 ft to 260 ft, a difference of 120 ft: gently rolling country.
Under the town center the state geologic map shows Huber/Lisbon/Barnwell Formations, undivided (clay, sand), from the Eocene, 34 to 56 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand, clay. Age: Pliocene, 2.6 to 5.3 million years old. About 11 mi of the line.
Clay, sand. Age: Eocene, 34 to 56 million years old. About 10 mi of the line.
Fine-detrital. Age: Quaternary, less than 2.6 million years old. About 1 mi of the line.
Sand, gravel. Age: Tertiary Neogene to Quaternary, less than 23 million years old. About 1 mi of the line.
Limestone, sand. Age: Pleistocene, less than 2.6 million years old. About 0.4 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Allendale reaches the Atlantic Ocean by way of the Coosawhatchie and the Broad: about 70 river miles.
50 miles of the trip are on the Coosawhatchie.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Allendale; river miles along the main stem, rounded.
