Sand and Gravel
Deposits of sand and gravel are widely distributed across all of Arkansas. Major deposits are present as sedimentary units, on talus slopes, and as alluvial deposits in the flood plains, beds, and terraces of rivers and streams. Most of these unconsolidated deposits may be mined from open pits. Certain areas of the state are particularly notable for the abundance of these resource materials. Some units of Early Cretaceous age in Pike, Howard, and Sevier Counties contain significant beds of sand and gravel, especially the Pike Gravel and Ultima Thule Gravel Members of the Trinity Formation, which range in thicknesses from 20 to 100 feet and 0 to 40 feet, respectively. Units of Late Cretaceous age which contain abundant sand and gravel are the Woodbine, Tokio, and Nacatoch Formations. Sand and gravel deposits are present in the Woodbine Formation in Howard and Sevier Counties. The Tokio contains recoverable sand and gravel in Clark, Pike, Howard, and Sevier Counties. Sand beds are present in the Nacatoch Formation in Clark, Hempstead, and Howard Counties. Tertiary gravel deposits are abundant in interstream divides of the Gulf Coastal Plain in southern Arkansas and on Crowley's Ridge in northeast Arkansas. Gravel and sand deposits on Crowley's Ridge extend from St. Francis County northward to the Missouri state line. Extensive Quaternary alluvial deposits of sand and gravel are present in the major river systems in the state. Dredging operations in the rivers, especially the Arkansas River, recover significant amounts of sand and gravel. Also, deposits are present locally within or adjacent to the beds of the smaller rivers and streams in the state. Significant deposits of cherty clay and sandy regolith in North Arkansas are utilized for road and construction fill material. In these deposits, rock fragments vary from rounded to highly angular.
The Arkansas State Highway and Transportation Department sets specific standards relating to the performance of construction materials, for sand and gravel used in Arkansas's highway projects. Use of specific deposits of sand and/or gravel depends on the performance of these materials in standardized engineering tests, including, but not limited to, size distribution, abrasion resistance, grain shape (roundness), and percentage of admixed fines (silt or clay).
A list of the major uses for construction sand and gravel includes: concrete aggregate; concrete products, including block, brick, and pipe; aggregate in asphalt and other bituminous mixtures; road-base material and road coverings; construction fill; snow and ice control; filtration purposes; and railroad ballast.
Worldwide, more sand and gravel is mined annually than any other industrial raw material. Immense quantities of this resource are in Arkansas, and are currently mined in about 75 percent of the 75 counties. Preliminary estimates of sand and gravel production in Arkansas for 2005 by the U. S. Geological Survey are nearly 10.6 million metric tons valued at $62,000,000. Nearly 50 percent was used for concrete aggregate and concrete products. Large tonnages were also used for aggregate in asphalt (and other bituminous mixtures) and for road-base material and rural road coverings.
References
Arkansas State Highway and Transportation Department, 1993, Standard Specifications for Highway Construction, edition of 1993: Little Rock, 794 p.