Soil genesis and classification of brown iron ore spoils on the western highland rim in Tennessee

A pedologic investigation was conducted on the Western Highland Rim in Tennessee on 140-170 year old brown iron ore spoils. The ore had formed in pockets at the interface between Mississippian Limestone and the overlying Cretaceous sands and gravels.

The objectives of this study were to 1) assess soil development on brown iron ore spoils; 2) compare properties in spoils to those in adjacent undisturbed soils; and 3) classify the spoils using Soil Taxonomy and the West Virginia Minesoil Classification System.

Two minesoil profiles (spoils) and two soil profiles on adjacent undisturbed soils (native) were sampled and described according to National Cooperative Soil Survey Standards. Total carbon, free iron, total elemental analysis, pH, exchangeable bases, cation exchange capacity, and exchangeable acidity were selected for laboratory chemical analysis. Variances of selected chemical properties were compared between sites using a grid sampling design and Hartley's test for homogeneity of variances.

Differences in origin of overburden material and the degree of weathering prior to disturbance accounted for morphological and chemical differences between the spoils. Spoil 1 had developed a cambic horizon and spoil 2 had not developed a diagnostic subsurface horizon. Bridging voids were observed in both spoils but not in the native soils. The spoils were enriched with iron oxides due to their association with the iron ore mining. Clay free ratios of fine sand to total sand plus silt [fs:(ts + si)] and titanium to zirconium (Ti/Zr) ratios consistently identified either differences between horizons and/or lithologic discontinuities of parent material designated by field morphology for all study sites.

Variations for total carbon, total aluminum, barium, manganese, phosphorus, titanium, and zirconium between 40-60 cm were not consistently significantly different between spoils and the native pedons at a 0.05 alpha level.

Properties defined for the Spolent suborder, of the West Virginia Minesoil Classification System, better described the spoil properties than Soil Taxonomy. Spoil 1 classified as a clayey, mixed, acid thermic Cherty Udispolept and spoil 2 classified as a clayey-skeletal, mixed, acid, thermic Cherty Udispolent using a slight modification of the West Virginia Minesoil Classification system.