Abstract

Eleven depositional sequences are present in the Middle and Upper Ordovician of the Nashville Dome. All but one lack lowstand systems tracts, and many display evidence of subaerial exposure such as paleokarst or regional erosional truncation at their sequence boundaries, which are combined with transgressive surfaces. Features formed during the transgression, such as hardgrounds, are more prominent at most sequence boundaries than are those features related to subaerial exposure. All sequences have maximum flooding zones with aggradational stacking rather than discrete maximum flooding surfaces. Condensation features are much more common at transgressive surfaces than within the maximum flooding zone. The expression of these parasequences and sequences changes with the onset of the Taconic orogeny. Although parasequences from equivalent depositional environments can be recognized before and after the onset of the orogeny, their facies composition changes completely. Sequences following the orogeny display fewer paleokarst features, more pyritized and iron-stained hardgrounds at flooding surfaces and transgressive surfaces, and more phosphatic lags and mineralization at transgressive surfaces than those preceding the orogeny. A relative sea-level curve for the Nashville Dome has a long-term (> 5 m.y.) component presumably dominated by subsidence and a short-term (1-3 m.y.) component consisting of 10-50 m fluctuations that is primarily the result of eustasy.

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