Abstract

The Greenwich slice of the Hamburg klippe, a Taconic allochthon in the central Appalachian orogen, is part of an inferred subduction complex related to early Paleozoic crustal convergence. It is composed chiefly of fault-bounded, coarsening-upward sequences of pelagic deposits (Lower to Middle Ordovician) overlain by thick sequences of channelized turbidite sandstone and hemi-pelagic mudstone (Middle Ordovician). The coarsening-upward sequences are interpreted to reflect migration of a site on oceanic lithosphere into a trench where turbidites and hemipelagic mudstone accumulated in Middle Ordovician time. Paleoflow in the channelized turbidite facies was predominantly longitudinal (northeast-southwest). Additionally, basin plain and outer-fan turbidite facies are conspicuously absent, and there are no proximal-to-distal sedimentologic variations along the length of the Greenwich slice. The turbidite deposits may have been transported in axially deflected channels that were part of an elongate submarine fan that occupied the floor of the trench. Alternatively, sedimentologic characteristics of these deposits can be explained by transportation of sediment in laterally migrating channels along the floor of a large trench axis channel.

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