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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 8. (August)

First Page: 1176

Last Page: 1177

Title: A Model for Faunal Succession and Reef Growth in Edgecliff Bioherms (Middle Devonian Onondaga Formation): ABSTRACT

Author(s): Thomas H. Wolosz

Article Type: Meeting abstract

Abstract:

Two small bioherms from the Edgecliff Member of the Onondaga Formation in Greene County, eastern New York, have been studied in order to formulate a model for Edgecliff reef development. Roberts Hill reef is approximately 720 ft (220 m) in length and 50 ft

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(15 m) thick, while Albrights reef (an erosional remnant) is 480 ft (146 m) in length and 13 ft (4 m) thick. Both exhibit an overall faunal succession showing both lateral and vertical trends which closely agree with the description of subsurface pinnacle reefs from south-central New York by Kissling (1979). Similar to these larger structures, the absence of stromatoporoids, and the subordinate role of massive favositids result in the lack of a true framestone core. Mound development was due almost entirely to the abundant growth of colonial rugosans which created a bafflestone core.

The core of the mound was constructed by a succession of three genera of colonial rugosans, all of which exhibit the same spreading phaceloid morphology, but with corallite branches being small and delicate in Acinophyllum, thick and robust in Cyathocylindrium, and intermediate in size in Cylindrophyllum. Initial core growth began on the carbonate mud sea-floor of the basal Edgecliff with the formation of thickets of Acinophyllum which developed into low bafflestone mounds. Core growth was continued by Cylindrophyllum, then capped by Cyathocylindrium. Surrounding this rugosan core, low-angle (8 to 10°) crinoidal packestone flanks developed which were colonized by large favositid colonies which show a dominance change from Emmonsia in the fore-reef to Favosites in the back-reef. H wever, these favositids acted only as minor sediment stabilizers.

The final stage of reef growth at Roberts Hill consisted of a recolonization of the fore-reef crinoidal packestones by the original core building fauna, with Cyathocylindrium acting as the initial recolonizer, followed by a mixed assemblage of Cylindrophyllum and Eridophyllum (another phaceloid rugosan). A repeated cycle of crinoidal flank formation, followed by rugosan colonization of these flanks, could extend both the lateral and vertical growth of the mound and result in large structures similar in size to those found in the subsurface in south-central New York.

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