Sedimentology and petrology of the Eocene Memphis Sand and younger terrace deposits in surface exposures of western Tennessee


Sedimentological and petrologic analysis of the Eocene Memphis Sand was conducted within a stratigraphic context during mapping of surface exposures in western Tennessee. Lithologic characteristics and heavy mineral assemblages support a tripartite division of the Memphis Sand into lower, middle, and upper informal members, as proposed by Hundt (2008) and Waldron and others (2011). The predominance of massive to trough and planar cross-bedded fine- to medium-grained sand with common intraclasts of root-trace bearing clay and minor interbedded laminated to massive silty clay with root traces indicate fluvial depositional environments ranging from meandering to low-sinuosity low-gradient stream existed in the study area. The Memphis Sand is disconformably overlain by 1 to 2 m of late Cenozoic (Pliocene?) fluvial terrace deposits that represent reworking of Memphis Sand and other Mississippi embayment strata. Postdepositional weathering and paleosol development on both the Memphis Sand and overlying fluvial terrace deposits indicates two periods of landscape stability and soil development under warm, humid conditions during the late Cenozoic. The presence of overlying Quaternary loess and accumulation of silicate clay and iron oxides in the two paleosols present impediments to recharge to the Memphis aquifer, the hydrostratigraphic equivalent to the Memphis Sand, beneath upland surfaces in western Tennessee.

Publication Title

Southeastern Geology

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