Ancient examples of beach sandstones
An excellent subsurface example of an offshore bar is present in southeastern Ohio, extending from Gallia County north to Muskingum County (Fig. 31). This bar is composed of “Second Berea” sandstone, which is Early Mississippian. This offshore bar fringes the southeastern part of a large, south- trending deltaic wedge of redbeds (Bedford), which also are Early Mississippian. Both this delta and the “Second Berea” sandstone are described and illustrated by Pepper et al. (1954) in a classic paper. The remarkable part of this study is that it was based almost entirely on drillers’ logs and outcrop data because almost no electric log data were available for this area at the time of the investigation. They used more than 1,300 drillers’ logs in outlining the shape, contouring the variations in thickness, and plotting cross sections of this offshore bar. They (Pepper et al., 1954, p. 56) described the “Second Berea sand” as
… an ancient shoreline deposit strongly resembling a modern barrier bar, such as those along the Gulf Coast of Texas. The sand body is about 185 miles long, 3 to 15 miles wide. The relatively straight eastern margin is the seaward side of the offshore bar, and the irregular western margin is the result of unequal deposition in the lagoon on the landward side of the bar.
Figures & Tables
Though Memoir 21 was first published in 1974, the concepts and illustrations are timeless for those interested in stratigraphic exploration for sandstone reservoirs. Quickly the reader will note the same relationships in sequence stratigraphy recognized by the author. For university earth science majors and less experienced members of the energy industry, the CD is presented as a reference work. The concepts of depositional control on the distribution of sandstone reservoirs is critical to understand no matter the terminology used. With the kind permission of Dr. Daniel A. Busch, this memoir now can become part of your exploration library.