LATE MISSISSIPPIAN SEDIMENTATION ON EASTERN AND EAST-CENTRAL LAURUSSIA: INTERACTIONS BETWEEN NEOACADIAN AND OUACHITA TECTONISM, EUSTASY, AND PALEOCLIMATE

Late Mississippian sediments in east and east-central Laurussia are platform/ramp carbonates (Tuscumbia, Monteagle, Bangor, Newman, Slade, Maxville, and Greenbrier limestones) overlain by marginal-marine/terrestrial clastics (Pennington and Mauch Chunk groups), truncated by a regional unconformity. The carbonates and clastics are part of a larger flexural sequence begun at the Devonian-Mississippian transition with the advent of Neoacadian orogeny, involving dextral transpression between the Carolina terrane and the southeastern margin of Laurussia. The flexural sequence begins with black shales overlain by the extensive Price-Pocono, Grainger, or Borden delta system. This extensive clastic wedge represents the transportation of clastic debris from Neoacadian highlands into the foreland basin and adjacent areas. Deltaic sedimentation continued until the Osage-Meramec (early Viséan) transition, when eustatic lowstand coupled with bulge uplift cut off clastic supply, setting the stage for carbonate deposition. Delta destruction left behind a platform/ramp setting with little clastic influx, which, when combined with lowstand, shallow-water conditions in an evaporative subtropical climate, produced ideal conditions for carbonate deposition. Hence, from the Osage-Meramec transition to mid-Chesterian time (early Viséan–early Serpukhovian), widespread carbonate deposition predominated across the area. These carbonates reflect deep-ramp to paleosol environments, which were locally altered by reactivation of basement faults during coeval northward Ouachita bulge migration. By Late Chesterian time, Neoacadian unloading-type relaxation produced a widespread, cratonward-prograding wedge of largely Upper Mississippian (Serpukhovian; Late Chesterian) marginal-marine and terrestrial clastic sediments in the Pennington and Mauch Chunk groups. The great extent and thickness of these units are probably related to the fact, that by Late Chesterian time, the area had moved into the humid equatorial zone which favored clastic deposition. This clastic deposition continued into earliest Pennsylvanian time when the sequence was truncated on the sub-Absaroka unconformity, marking eustatic drawdown and advent of Alleghanian orogeny. Late Mississippian sediments in east and east-central Laurussia are parts of a complete flexural tectophase cycle that is largely a response to the transpressional nature of Neoacadian orogeny. Paleoclimate, eustasy, and Ouachita tectonism were secondary influences.