Detailed Lithostratigraphy And Faunal Distribution Through A Sequence Of Punctuated Aggradational Cycles (PACS) In The Manlius Formation Of Central New York State

Abstract

A portion of the Upper Olney and Elmwood Members of the Manlius Formation (Lower Devonian, Helderberg Group} in central New York State was deposited as a sequence of upward-shallowing units, 1.5 to 10.5 feet thick, separated by transgressive (deepening) sur­faces. These cycles of deposition have been called Punctuated Agg­radational Cycles, or PACs, after Goodwin and Anderson (1980b). With each rapid transgression, pronounced changes in paleogeography occurred episodically over the entire study interval (a lateral dis­tance of 50 miles oblique to the basin axis). After each rapid trans­gression, gradual changes in paleogeography occurred as sediments and/or stromatoporoid bioherms aggraded towards a static sea level. The highest occurrence of vertical burrows and/or the lowest occurrence of well-formed algal laminites defines the maximum normal high sea level position achieved in a PAC. Correlation of PAC sequences on the basis of relative spacings of these maximum high tide positions, resulted in recognition of actual paleotopographies ·developed following each rapid transgression. Shallow marine, level bottom paleocommunities of this study interval were developed allogenically in response to sea level changes associated with the formation of PACs. Long-term, upward-decreasing diversity of taxa occurred within each PAC 8:s the "climax" community of transgressive, short-term succession was modified or replaced in re­sponse to a gradual shallowing of the environment. The shallowing was caused by sediment aggradation and/or stromatoporoid growth.