Using Fischer plots to identify third-order sequences in the Middle Devonian, mixed carbonate-siliciclastic strata of West Virginia
Using Fischer plots to identify third-order sequences in the Middle Devonian, mixed carbonate-siliciclastic strata of West Virginia (in The Appalachian geology of John M. Dennison; rocks, people, and a few good restaurants along the way, Katharine Lee Avary (editor), Kenneth O. Hasson (editor) and Richard J. Diecchio (editor))
Special Paper - Geological Society of America (August 2020) 545: 55-65
- Appalachian Basin
- carbonate rocks
- correlation
- Devonian
- Hamilton Group
- lithofacies
- lithostratigraphy
- Mahantango Formation
- Marcellus Shale
- Middle Devonian
- North America
- Onondaga Limestone
- outcrops
- Paleozoic
- Preston County West Virginia
- sedimentary rocks
- sequence stratigraphy
- siliciclastics
- thickness
- Tully Limestone
- United States
- well logs
- West Virginia
- Wetzel County West Virginia
- Burket Shale
This study examines the usefulness of accommodation plots (Fischer plots) as a means of correlating mixed carbonate-siliciclastic strata in the subsurface. Fischer plots have been widely used to extract accommodation changes from carbonate platforms, but there are few published studies of siliciclastic or mixed carbonate-siliciclastic environments. The Middle Devonian of the Appalachian Basin is penetrated by thousands of wells, is exposed in numerous exceptional outcrops, and is an excellent place to test the usefulness of accommodation history plots as correlation tools. In the past, researchers have used cores, well cuttings, well logs, and outcrop gamma-ray profiles to correlate between outcrop and subsurface data, but all these methods have their limitations. Gamma-ray logs for wells penetrating the Middle Devonian from eight locations, from Preston County in the east to Wetzel County, West Virginia, in the west, were used in this study. Accommodation cycle thicknesses were measured from gamma-ray logs, printed at a vertical scale of one inch per ten feet (2.5 cm/3 m). The accommodation cycle thickness data were entered into Antun Husinec's FISCHERPLOTS program to produce accommodation plots. Next, well-documented, outcrop-based sequence stratigraphy was used to help interpret the results of the accommodation plots. This study demonstrates that using accommodation plots is a novel way of overcoming the uncertainties and biases of other methods. The use of this approach in other mixed carbonate-siliciclastic successions with abundant subsurface data would help to demonstrate that Fischer plots are a novel and useful approach that can help remove many of the uncertainties and biases encountered in stratigraphic correlation.