The Catskill Delta complex and the Acadian Orogeny: A model

Abstract

The Catskill Delta complex is interpreted to be the aggregate of delta-alluvial wedges and associated facies that developed in the central Appalachians and on adjacent parts of the stable craton from the Early-Middle Devonian transition to the Middle Mississippian during the Acadian orogeny.Recent interpretations of the Acadian orogeny suggest that it probably was related to oblique convergence and transcurrent movement along a major strike-slip fault zone separating the eastern margin of the North American landmass from a linear continental fragment called the Avalon terrane. Distribution of clastic wedges and basinal deposits resulting from this orogeny support a general southwestward progression of orogeny and indicate that the major clastic wedges emanated from areas near promontories on the continental margin during successive phases of Acadian deformation. Three and possibly four such tectophases have been noted. Each tectophase appears to represent increased convergence or possible collision between a specific continental promontory and the Avalon terrane, but some delta development occurred continually along many parts of the orogen in response to each tectophase. The four tectophases are: (1) Collision near the St. Lawrence promontory during the Early-Middle Devonian transition with initiation of the Catskill Delta complex represented by the Needmore and Esopus shales and associated clastics near promontories. (2) Southward migration of deformation and collision near the New York promontory during the Middle Devonian with the development of a large peripheral basin having an east-dipping, western paleoslope. This basin was filled with cyclic delta clastics and carbonates of the Hamilton Group and Tully Limestone. (3) Southward migration of deformation and collision near the Virginia promontory during the LateDevonian to earliest Mississippian accompanied by intense clastic influx of the Geneseethrough-Canadaway groups. As a result, the basin was progressively filled from the east so that basinal environments migrated westward out of the peripheral basin and onto adjacent parts of the stable craton. Eventually the basin was filled and a regional west-dipping paleoslope was established. (4) Migration of deformation southward from the Virginia promontory during the Early to Middle Mississippian as basinal environments in cratonic seas were destroyed and Pocono and equivalent clastic wedges essentially filled the epicontinental sea. Middle Mississippian carbonates mark the end of the Acadian orogeny and Catskill Delta complex.

Modeling the nature and development of major paleozoic clastic wedges in the Appalachian Basin, USA

“…Closely following the Caledonian cycle of orogeny, however, was the Early Devonian (Pragian; mid-Ulsterian) inception of convergence by one or more Avalonian terranes with the southeastern margin of Laurussia. This episode of convergence, called the Acadian Orogeny, generated some of the best-known and variously interpreted delta complexes in the Appalachian Basin (Friedman and Johnson, 1966;Woodrow and Sevon, 1985;Faill, 1985;Ettensohn, 1985a). Convergence was probably transpressional, and beginning in late Early Devonian (Pragian-Emsian; mid-Ulsterian) time, progressed southwestwardly along the southeastern margin of Laurussia (Ettensohn, 1985a(Ettensohn, , 1987, resulting in a series of thick, clastic sequences that tracked the southwesterly progress of orogeny (Ettensohn, 1985a(Ettensohn, ,b, 1987.…”

“…The word tectophase is used here in the sense of Johnson (1971) to reflect all the events in a particular pulse or phase of orogeny, mostly concentrated at a certain time and place along an orogenic belt. Ettensohn (1985aEttensohn ( , 1987Ettensohn ( , 1994, moreover, showed that each tectophase produced a third-order sequence of sediments, including delta complexes, bound by unconformities, and that the progression of an orogeny could be tracked by mapping the distribution of the sequences, both parallel and perpendicular to the strike of the foreland basin. Despite differing ages, each of the early Appalachian sequences contains a similarly ordered succession of lithologies, suggesting that each broad lithologic type in the sequence results from a specific flexural response to various phases of deformational loading or lithospheric relaxation during a tectophase in the orogen.…”

Joint interaction with embedded concretions: joint loading configurations inferred from propagation paths

“…1). The Geneseo Formation is the basal unit of the Upper Devonian Genesee Group, part of the Catskill Delta complex deposited during the Acadian Orogeny (Ettensohn, 1985). The Geneseo Formation is a homogeneous black shale, about 30 m thick in the study area, that crops out in an E±W-trending band across the central Appalachian Plateau of New York.…”

Characterization of Bedding-Parallel Fractures in Shale - Morphology, Size Distribution and Spatial Organization

“…These promontories served to localize shortening and deformation (Figure 1-7). They went through greater compression which led to greater flexural subsidence, and formed four major depocenters (Ettensohn, 1985(Ettensohn, , 1994(Ettensohn, , 2008Ferrill and Thomas, 1988;Lash and Engelder, 2011;Lavoie, 2008).…”