The Devonian Catskill Sea of the Appalachian region was stratified much of the time as recorded by the deposition in it of black shale and evaporites. Submarine topography which developed along the southeastern perimeter of the sea consisted of a basin margin and a gently sloping clinoform constructed by sediment progradation. Intersection of the surface of stratification (pycnocline) with the seafloor marked the basin margin-clinoform junction and it caused a separation of sedimentary processes. Shoreward of the intersection, on the basin margin, bottom flow driven by various current-producing phenomena, transported, deposited and reworked sediment. A complex mosaic of facies resulted, including a typical suite of lenticular sandstone, bioturbated shales and mudstones, most of which are abundantly fossiliferous. Basinward of the intersection, on the clinoform, density currents originating at or shoreward of the intersection moved down the clinoform onto the basin floor. Relatively simple facies accumulated, including turbidites and other, pelagic sediments, with very few fossils. At the intersection, internal waves moved along the pycnocline, shoaled, broke and reworked sediment, leaving a record of relatively thick sandstones, some with hummocky cross-bedding. This separation of process is likely to have been a hallmark of sedimentation in epicontinental seas where stratification can be inferred.
Figures & Tables
The Shelfbreak: Critical Interface on Continental Margins
The shelfbreak is that point where the first major change in gradient occurs on the outermost edge of the continental shelf. Although this environment delimits the boundary between two principal and well-defined provinces, the continental shelf and slope - and thus is of the first order of importance on continental margins - it has received surprisingly little specific attention in either modern oceans or in the rock record. This volume, the first compendium dedicated specifically to the shelfbreak, was derived from an SEPM Research Symposium convened at the joint Annual Meeting of SEPM and AAPG on June 2, 1981. The material is organized in a manner to illustrate examples of the shelfbreak in both modern oceans and the rock record.