Introduction to the Physiographic Regions
The five physiographic regions of Alabama are differentiated on the basis of topographic relief, rock types, and geologic structure. From north to south these are the Central Basin, Interior Low Plateaus, Appalachian Plateaus, Valley and Ridge, Piedmont, and Coastal Plain provinces (figure). The next sections include revised excerpts from the Stratigraphy of Alabama (GSA Circular 140) describing the geology within each province.
Physiographic regions of Alabama (Ebersole and others, 2019). Click to expand.
Central Basin and Plateaus Resources
Limestone is quarried for aggregate and dimension stone from the Bangor (figure), Monteagle, and Tuscumbia Limestones in the Plateaus. Other mineral resources in the Plateaus include asphaltic limestone, barite, bauxite, tripoli, iron ore, and sand and gravel (Smith, 1983).
Valley and Ridge Resources
The Valley and Ridge province contains a number of mineral commodities. Limestone is mined from the Conasauga Formation, Longview Limestone, Newala Limestone, Lenoir Limestone, and Little Oak Limestone. Other geologic resources include dolomite, shale, kaolin, chert, and sand and gravel. Resources available, but not presently commercially produced include barite, red iron ore (hematite), brown iron ore (limonite) (figure), tripoli, manganese, lead, zinc, and bauxite. Hematite and limonite were heavily mined in the 1800s and early 1900s as part of the early iron-making industry
Piedmont resources
A variety of metallic and non-metallic resources are in the Piedmont. Metallic mineralization in the Alabama Piedmont is concentrated in the Northern Piedmont district with Cleburne, Clay, Coosa, and Tallapoosa Counties having gold (figure) and tin production through the years. Arsenic, columbium-tantalum, lead, manganese, molybdenum, tungsten, vanadium, and zinc also occur in the Northern Piedmont, but in lesser quantities.
Nonmetallic resources from the Piedmont include anthophyllite (asbestos), barite, beryl, graphite, kaolin, kyanite, mica, silica, talc, and uranium. Graphite production was once one of the largest mineral industries in the Piedmont, and mica production spanned more than 100 years. Marble is produced from stone quarried from the Sylacauga Marble Group (figure). Talc has been mined from metamorphosed dolomite, and talc and asbestos have been mined from ultramafic rocks.
Construction materials represent the major geologic resource extraction activity in the Piedmont. Marble, crushed stone, and sand and gravel are produced from a variety of sources; dimension stone is also produced; and crushed stone, principally granite and granitic gneiss, has been produced from a variety of different intrusive bodies.
East Gulf Coastal Plain Resources
The East Gulf Coastal Plain is a source of a wide variety of resources, and all the materials necessary for construction are abundant in the area. Sand and gravel are mined in almost every county in south Alabama and much of it is used as aggregate or in road construction. Calcareous rocks suitable for the manufacture of cement are present in the chalks of the Selma Group and the Eocene and Oligocene limestone formations. Clay (figure) such as bentonite, high-alumina clay, kaolin, and zeolite also occur in the Coastal Plain. Clays for bricks and tiles occur in western Alabama and high-alumina clays, including kaolin, used for refractories occur in the southeastern part of the state. Bentonite used as bond for foundry sand and for absorbents occurs in Lowndes and Crenshaw Counties. Expansive clay for aggregate and pet supplies occurs in the Porters Creek Formation. Zeolite minerals are common constituents of the Clayton, Nanafalia and Tallahatta Formations. Brine suitable for use in industrial chemicals is solution-mined from a shallow salt dome near McIntosh in Washington County.
Sulfur is a by-product of the cleansing and extraction plants which process the oil, gas, and condensate produced from formations of Jurassic age. Sulfur is important in the production of many chemicals and the sulfur produced at the extraction plants adds considerably to the raw material wealth of the state.