Abstract

Deltaic sediments are common in the stratigraphic record, but they have not been well documented. An exception is the Devonian Catskill deltaic complex of southeastern New York and northeastern Pennsylvania, which has been studied by literally hundreds of geologists and was classically described by Barrell in the early part of this century. The Mississippi Delta has been generally taken as a model of Recent deltaic sedimentation and the Catskill complex as the ancient type example.

This paper briefly reviews the geology of the Catskill deltaic complex, restates the concepts of Barrell, and contrasts the Catskill deltaic plain with that of some modern deltas. In the constructional phases of some recent deltas, such as the Mississippi Delta, sand bodies, comprise only a minor part of the total sediment, but in the Catskill complex they are the dominant component. This is a function of the proximity of the Catskill deltaic plain to the source terrain, in contrast to some of the recent deltas, which are adjacent to low-relief coastal plains.

The term, "tectonic delta complex," is proposed for a deltaic complex built into a marine basin contiguous to an active mountain front and dominated by orogenic sandstones.