GEOLOGY OF THE ENVILLE 7.5-MINUTE QUADRANGLE IN CHESTER, HENDERSON, AND MCNAIRY COUNTIES, TENNESSEE

The Enville 7.5-minute quadrangle (latitudes 35°30՛00՛՛N to 35°22՛30՛՛N; longitudes 88°30՛00՛՛W to 88°22՛30՛՛W) is located in Chester, Henderson, and McNairy counties, Tennessee. The objective of this study is to map Upper Cretaceous lithofacies of the Demopolis Formation, Coon Creek Formation, and McNairy Sand in the northern Mississippi Embayment at the 1:24,000 scale. This work advances our understanding of regional stratigraphic relationships and provides insight into the spatial-temporal distribution of heavy mineral sand deposits.

The Demopolis Formation consists of light-gray to greenish-gray to yellowish-brown, very fine- to fine-grained, glauconitic siltstone, claystone, and silty clay/clayey silt deposited in a shallow, nearshore marine environment. The stratigraphic contact between the Demopolis and Coon Creek formations is gradational and not readily exposed in the Enville quadrangle. The Coon Creek Formation consists of light- to dark-gray to brown to reddish-brown, very fine- to medium-grained, thinly- to thickly-bedded, micaceous, sporadically fossiliferous marl, clay, silty clay/clayey silt, clayey-to-silty sandstone and sand beds with regular ironstone concretions. Fossil mollusks are sparsely distributed in the marl, clay, and silty clay/clayey silt beds, typically in the lower part of the formation associated with nearshore, transitional estuarine or delta platform environments. The upper part of the unit coarsens towards the Coon Creek-McNairy Sand contact and primarily consists of micaceous and ferruginous clayey to silty sand and fine- to medium-grained sandstone with frequent ironstone concretions. The presence of interbedded silt to sandy-clay beds and ironstone concretions throughout the lower Coon Creek Formation, along with the recurrence of dark-gray and gray, sometimes micaceous, clayey silt/silty clay layers near the Coon Creek-McNairy Sand contact, indicates cyclical facies changes throughout the formation. The contact between the Coon Creek Formation and the overlying McNairy Sand is gradational and records continued sea level regression and progradation of shoreline lithofacies. The McNairy Sand consists of tan to reddish-brown to rust-red, medium- to coarse-grained, laminated, cross-bedded, frequently ferruginous, sporadically micaceous silty-sand and sandstone.