Geologic Map of Arkansas
Arrangement (c) 2000 Andrew Alden, licensed to About.com. Map base from U.S. Geological Survey (fair use policy)
Arkansas stretches from the Mississippi River on its eastern edge, where historic movement of the riverbed has left behind the original state borderlines, to the more settled Paleozoic rocks of the Ouachita Mountains (the broad purple lobes) on the west and the Boston Mountains to their north. The light-colored streaks represent the recent sediments of (from left to right) the Red, Ouachita, Saline, Arkansas, and White rivers.
The striking diagonal boundary across the heart of the state is the edge of the Mississippi Embayment, a wide trough in the North American craton where once, long ago, the continent tried to split. The crack has remained seismically active ever since. Just north of the state line along the Mississippi River is where the great New Madrid earthquakes of 1811–12 occurred.
The Ouachita Mountains are actually part of the same foldbelt as the Appalachian range, separated from it by the Mississippi Embayment. Like the Appalachians, these rocks produce coal and natural gas as well as various metals. The southwestern corner of the state yields petroleum from its early Cenozoic strata. And just on the border between these two regions, a rare body of lamproite is the only diamond-producing locality in the United States.
The mid-sized version of this map is 1200x1050 pixels and weighs 700 KB. It looks pretty good: The small type is not legible, but you can check the colors against the explanation (1200x1200, 300 KB) to identify the different rock units.
The big version is 2000x1740 pixels and weighs 2 MB. But I've prepared an even bigger version in four pieces, each one 2300x2000 pixels:
Northwest quadrant (3 MB)
Northeast quadrant (2.8 MB)
Southwest quadrant (3 MB)
Southeast quadrant (2 MB)
Again, the explanation is separate.
More Arkansas resources from About.com:
About Little Rock
Arkansas Maps
Arkansas Geography, State Symbols & Facts
Arkansas Campgrounds
Arkansas Archaeology
Back to Geologic Maps of the States
