Smith, Gerald J.1, Robert D. Jacobi1
(1) SUNY at Buffalo, Buffalo, NY
ABSTRACT: Upper Devonian Sands in New York State: Examples of Storm-Generated Offshore Sand-Ridges
The major sandstone bodies within the Upper Devonian Canadaway and Conneaut groups have been described as lenticular sands for well over 100 years. These sands include the historically productive Bradford, Sugar Run and Chipmunk reservoirs in New York and Pennsylvania. The lenticular nature of the deposits, combined with growth faults and erosion, has made correlation of these sands extremely difficult. Using key marker units, we have utilized outcrops and well-logs to describe 7 major lenticular sandstones in these groups. The sandstones we focus on herein lie stratigraphically above the shoreface sandstones of the Rushford Formation.
All of the sandstones are sharp-based; all exhibit thickly-bedded, swaly-cross stratification. Internal erosional surfaces are commonplace, as are sporadic, thin lenses of coquinite. The maximum thickness of a sandstone body ranges from 3 to 12 meters, individual sandstone packets thin and become interbedded with gray shales and siltstones laterally. Sporadic occurrences of load-casts and rip-up clasts suggest rapid deposition in a high energy environment. The sandstones contain bi-directional paleoflow indicators, but lack mud-drapes and herringbone bedding that would indicate a dominating tidal influence. The surrounding interbedded gray shales, silts and thin sandstones that surround the sandstone lenses commonly contain storm-related structures.
The sandstones appear to be comprised of several separate storm deposits that have spatially coincident maximum sandstone thicknesses with the accumulation of many events occurring over an initial ridge. As the change in relative sea-level does not appear to be major, we conclude that the sand-ridges mark the bases of parasequences.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.