| Abstract/Notes | The area of outcrop of the Arkansas Paleozoic rocks occupies essentially the northwestern half of the State and covers about 25,000 square miles. Unlike the low-lying Gulf Coastal Plain, on the southeast, it is a fairly rugged highland. It is divisible into several physiographic provinces, of which the larger are the Ozark Highlands, which lie north of the Arkansas River; the Arkansas Valley, through which the river flows; and the Ouachita Mountains, which lie between the Arkansas Valley and the Gulf Coastal Plain on the south and southeast. The Ozark Highlands are made up of deeply dissected plateaus, which rise toward the south and reach a maximum height of about 2,400 feet above sea level. The Arkansas Valley is a westward-trending structural topographic trough, above whose low, undulating surface rise sharp-topped ridges and flat-crested, mesa-like mountains, which attain a maximum height of more than 2,800 feet. The Ouachita Mountains are a series of nearly westward-trending rather rugged ridges of complex structure. The highest peaks reach elevations of about 2,700 feet above sea level and rise 1,500 feet above the adjacent lowlands. |
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