The Marietta 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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Marietta’s center stands about 840 ft above sea level. Within three miles the land runs from 750 ft to 920 ft, a difference of 170 ft: gently rolling country.
Under the town center the state geologic map shows Caddo Formation (limestone, shale, marlstone), from the Early Cretaceous, 100 to 145 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 55×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone, shale, marlstone. Age: Early Cretaceous, 100 to 145 million years old. About 7 mi of the line.
Claystone. Age: Early Cretaceous, 100 to 145 million years old. About 5 mi of the line.
Sandstone. Age: Early Cretaceous, 100 to 145 million years old. About 4 mi of the line.
Limestone. Age: Early Cretaceous, 100 to 145 million years old. About 3 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Sandstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 3 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 Marietta reaches the Gulf of America by way of Bills Creek, Clouds Branch, the Red River, the Atchafalaya and the Lower Atchafalaya: about 900 river miles.
750 miles of the trip are on the Red River.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Marietta; river miles along the main stem, rounded.
