Stratigraphic Analysis Of The Lower New Scotland Formation: An Episodic Perspective

Abstract

Application of the PAC Hypothesis to the deep shelf carbonate facies of the lower New Scotland Formation (Lower Devonian) results in the complete division of this interval into IO PACs that may be correlated throughout the Hudson Valley of Eastern New York State. These deep water PACs primarily consist of terrigenous black shale alternating with limestone beds, the black shale being concentrated at the bases of PACs. Sedimentological analysis suggests that the shales represent "background" deposition of fine suspended sediment and the limestones are event deposits, possibly turbidites and/or tempestites. In contrast to PACs recognized in much shallower facies, a shallowing-upward motif is absent in lower New Scotland PACs. The absence of a shallowing facies pattern suggests that abrupt base-level rises had little direct depth related impact on the deep lower New Scotland shelf. Instead facies change within these PACs was an indirect response related to the supply of transported carbonate sediment into the deep shelf. Comparative analysis of the magnitude of facies change at the base of each lower New Scotland PAC indicates that the sequence of PACs in the study interval is the result of 1 major punctuation event followed by 10 minor punctuation events. General vertical patterns of facies change from PAC to PAC suggest that the deepest point in the lower New Scotland is reached at the base of PAC 7. Lateral facies analysis within PACs leads to the recognition of a proximal to distal trend from Kingston to Callanan Quarry (south to north), a distance of approximately 50 miles. Lower New Scotland PACs at Kingston are characterized by relatively shallower facies, while at Callanan Quarry, these PACs are characterized by deeper, more basinal facies. The lateral persistence of the 10 New Scotland deep water PACs over 50 miles precludes an autogenic origin of these cycles. Rather, accumulation of the deep shelf facies of the lower New Scotland, like the shallower facies of the Kalkberg, Coeymans, and Manlius Formations was principally controlled by small-scale base-level fluctuations as predicted by the PAC hypothesis.