A Sub-Pennsylvanian Paleovalley System in the Central Appalachian Basin and its Implications for Tectonic and Eustatic Controls on the Origin of the Regional Mississippian-Pennsylvanian Unconformity
Jack D. Beuthin, 1994. "A Sub-Pennsylvanian Paleovalley System in the Central Appalachian Basin and its Implications for Tectonic and Eustatic Controls on the Origin of the Regional Mississippian-Pennsylvanian Unconformity", Tectonic and Eustatic Controls on Sedimentary Cycles, John M. Dennison, Frank R. Ettensohn
Download citation file:
Paleodrainage mapping of the Mississippian-Pennsylvanian unconformity in northwestern West Virginia verifies the existence of an incised, sub-Pennsylvanian paleovalley system there that extends for over 130 km. The paleovalleys are filled mostly with quartzose sandstones of the New River Formation. This paleovalley system was carved by a southwest-draining network of rivers that was rejuvenated during the mid-Carboniferous. Bedload-dominated streams that occupied the paleovalleys deposited most of the valley-fill sediment.
Regional paleodrainage data indicate that the sub-Pennsylvanian paleovalleys in northwestern West Virginia form the middle reach of a major paleoriver system which includes the Middlesboro paleovalley in eastern Kentucky, the Sharon paleovalley in eastern Ohio, and the Perry paleovalley in southeastern Ohio. This regional paleodrainage network (herein named the Middlesboro-Sharon-Perry paleovalley system) transported sediment from the craton north of the central Appalachian basin to the mid-Carboniferous depocenter in southwestern Virginia. Although it has been previously suggested that maximum erosional development of the Mississippian-Pennsylvanian unconformity occurred during the Early Pennsylvanian, paleoslope considerations rule against an Early Pennsylvanian age for carving of the Middlesboro-Sharon-Perry paleovalley system. Existing biostratigraphic data from the mid-Carboniferous depocenter in southern West Virginia support the existence of an Upper Mississippian (Chokierian-Alportian stages of the Namurian Series) hiatus there, suggesting that incision of the Middlesboro-Sharon-Perry paleovalley system was dominantly a Late Mississippian (Chokierian-Alportian) event.
Uplift of the craton north of the central Appalachian basin combined with subsidence within the basin that increased in rate toward the mid-Carboniferous depocenter in southern West Virginia created the generally south-dipping paleoslope which the Middlesboro-Sharon-Perry paleoriver system drained. The regional paleodrainage picture rules against tectonic uplift of the Cincinnati arch as a key factor in driving the incision of the Middlesboro-Sharon-Perry paleovalley system. Carving of this paleovalley system apparently was driven by a previously documented, Late Mississippian (Chokierian-Alportian) eustatic sea-level drop. Regional tectonic uplift during the Early Pennsylvanian may have influenced erosional development of the Mississippian-Pennsylvanian after the Late Mississippian incision of the Middlesboro-Sharon-Perry paleodrainage system.
Figures & Tables
The collected volume begins with a brief perspective by one of the conveners, followed by articles in order of increasing stratigraphic age. Eustatic sea-level changes and tectonic warpings of basins are competing mechanisms for explaining many stratigraphic patterns. The model for sea-level changes should be developed first for a basin, since it is allocyclic and leads to a series of time bands in the strata. The residual effects should then be modeled for tectonic patterns affecting the depositional processes. Doing the reverse limits time constraints on the tectonic warping models and will blur the resolution of detailed time surfaces in the strata. Case histories of situations with both tectonic warping and time surfaces marked by sea-level events will lead to improved interpretations of earth history.