Geology of Washington County, Arkansas

Washington County embraces twenty-seven townships and an area of 569,600 acres, divided almost equally into valleys, plateaux and inclined surfaces or terraces. An idea of the general surface may be gained by considering the county to have once been a rolling plateau with for its southern, eastern and western margins the Boston Mountains and their several branches; then allowing Fayetteville’s region to be the highest point, with gentle slopes of the county to the northwest and northeast, you have the White River on the east and the Illinois River on the west, both with a bewildering network of tributaries washing out among the plateaus, the terraces and valleys, giving a somewhat “islanded” appearance. What is known as East Heights at Fayetteville has an altitude of 1,731 feet above sea level, while some valleys are probably not more than 1,000 feet above the sea. The Illinois River, with its main branches, Clear Creek, the Evansville, Ballard and Barren Forks, drain probably the largest part of the county, while the White River, and its Main, Middle and Southwest Forks cover the remainder excepting that part below the Boston Mountain ridge, which is drained chiefly by the tributaries of Frog Bayou and Lee’s Creek. The drainage is even, and the streams are fed almost entirely from splendid springs which burst from the mountain ledges, in some cases affording excellent water power at their source.

In geology few regions show the diversity observed in Washington County. Almost every geological period is represented, from the protruding ancient sandstones to the quarternary formation, which is most prevalent. According to David Dale Owen’s report the base rock of the county is the cherty barren limestone, although some of the deepest cuts on White River in the northeast exhibit black shale below that. The following lists show the superposition of rocks in various parts of the county, according to Prof. Owen’s approximation. In Townships 17 and 18, Range 29 west: (1) White, yellow and brown sandstone, some of cellular structure, 200 feet; (2) ferruginous and dark shales, 40 feet; (3) chert, 40 feet; (4) cherty limestone, 35 feet; (5) black cherty shale, 40 feet. In the ridge southeast of Fayetteville: (1) Sandstones of the mill grit series with peculiar fossils, 100 feet; (2) calcareous bands; (3) sandstone of the millstone grit series, cellular and carbonaceous, 125 feet; (4) shales, including eight inches of coal and fire clay, 40 feet; (5) sandstone, 6 feet; (6) pentrimital limestone, 4 feet; (7) shales, including an inch or two of coal, in the cut below Cato’s Spring; (8) Archimedes limestone, 30 feet; (9) shales, calcareous bands with pyrites, gypiferous shale, black shale with carbonate of iron, 40 feet. In Township 15, Range 29 west, on Wood’s branch, Middle Fork of White River: (1) Brown sandstone with amygdaloidal cavities; (2) (space concealed with shales); (3) Archimedes cavernous limestone; (4) grey and black shales, with perhaps some interstratified sandstone, and including, near its base, a band of dark fossiliferous, pyritiferous limestone, and segregations of carbonate of iron. Another section on the Middle Fork of White River: (1) Sandstone, probably underlaid with shale, 50 to 100 feet; (2) Archimedes, cavernous and concretionary limestone, 40 to 60 feet; (3) grey shale, pyritiferous limestone shale. In the ridge at the point where the road crosses East Fork of the Illinois River: (1) Soft brown sandstone, a few feet of limestone followed by sandstone, 80 feet; (2) ferruginous, sandy shales, 30 feet; (3) Archimedes limestone, 70 feet. The succession at Cane Hill: (1) Fine grained sandstone, 15 to 20 feet; (2) limestone, a few feet; (3) coarse yellow sandstone, 40 feet; (4) greenish grindstone grit, 45 to 70 feet; (5) Archimedes [p.139] limestone, 60 feet; (6) marly shales in the bed of the branch. Superposition from Cane College Hill to Barren Fork of the Illinois River: (1) Shistose sandstone of College Hill, Archimedes limestone over Boonesboro Spring, 45 feet; (2) dark shales, 10 to 15 feet; (3) freestone or building stone; (4) shale; (5) chert; (6) fossiliferous limestone; (7) sandstone; (8) chert and cherty limestone of the Barren Fork of Illinois River; (9) black shale. In Vineyard Township the succession is: (1) Fine grained silicious rock, approaching the texture of white stone in its character; (2) limestone; (3) shale; (4) yellow, coarse sandstone; (5) finer grained shistose sandstone of the character of grindstone grit; (6) Archimedes and other limestones; (7) dark shale rocks; (8) brown freestone; (9) shale; (10) fossiliferous chert; (11) fossiliferous limestone with marly and shaly partings; (12) chert; (13) cherty limestone; (14) black shale.

Although near Fayetteville the strata in places dip to a considerable degree, so that elevations occasionally may be due to that cause, the greater number of them are probably due to their composition of less easily eroded rock. The limestones have, through the action of water, become cavernous in many places, and this is no doubt the prevailing source of springs. The great variety of rock formation, from which the soils are formed by erosion and decomposition, gives rise to a marvelous variety of soils, which are so continually renewed that they seem inexhaustible.

The great variety of mineral resources are probably due to the results of the igneous disturbances farther south, which gives to the strata of Washington County its occasional dips. Prof. F. L. Harvey has given a remarkable list of minerals and rocks found in the State, and this county includes a large proportion of them.

It is estimated that 60 per cent of the whole area of the county is timber land, the leading varieties of wood being white oak, hickory, red oak, post oak, walnut, ash, elder, elm, dog-wood and locust. The timber is so important a feature and of so excellent a quality that the St. Paul branch of the “Frisco Railway” was built especially for making the timber accessible to supply several railways. At Fayetteville natural gas has been found in three different places, at the depths of 225, 140 and ninety feet. Its coal has not been developed, although there are evidences of a fair supply. The agricultural products are corn, wheat, grasses and clovers, oats, Irish and sweet potatoes, sorghum and tobacco, particularly; the sorghum cane is peculiarly suited to Washington County surroundings, and is rapidly acquiring importance. But little cotton is grown. The horticultural phase of the county is especially striking; its apples are first premium fruits wherever exhibited; peaches, grapes, pears, plums, cherries, berries and other small fruits follow, in excellence and abundance not far behind the apples. These, heretofore raised for home consumption, have, since the advent of the Frisco Railway, been raised almost exclusively for commercial purposes, and become famous throughout the country. Irish potatoes, onions, cabbage and turnips have increased manyfold in quality and abundance, and are shipped to Little Rock, Fort Smith, Springfield and other places.

Back to: Washington County, Arkansas History

Source: History of Benton, Washington, Carroll, Madison, Crawford, Franklin, and Sebastian Counties, Arkansas. Chicago, IL, USA: Goodspeed Publishing Co., 1889.

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