Supplemented graphic correlation; a powerful tool for paleontologists and nonpaleontologists

The graphic correlation technique of Shaw (1964) is not restricted to biostratigraphic applications. Supplemented graphic correlation (SGC) expands the original technique to include nonunique events (log patterns) to add to the understanding of the geologic history of an area. Nonunique events are evaluated in light of the biostratigraphic data and may be used to refine correlations provided that (1) the investigator has reason to believe that the log patterns respond to time-significant phenomena over the areal extent of the specific problem at hand, and (2) all nonunique events to be considered are tested for geologic reasonableness before they are used. Dinocyst and acritarch occurrence data and single-point resistance electric logs from three Paleocene to Eocene cores in the Virginia Coastal Plain illustrate the method. The two western cores show similar geologic histories, but the thickness in the northernmost core is approximately 30% greater. SGC reveals four episodes of deposition in the easternmost core relative to the western cores, During late Paleocene time, relative accumulation rates increased in an easterly direction. A major change in sediment source and supply occurred in early Eocene time when relative accumulation rates increased to the north. Graphic correlation combining biostratigraphic events and time-significant log-type data can increase resolution in correlation. Possible correlations are tested and refined during the graphic procedure and multiple lines of evidence are used to produce geologically reasonable, and informative, results.