T30 Geology across Geographic Boundaries: Identifying Challenges and Opportunities Related to the Creation of a Digital Geologic Map of the United States by the End of This Decade (Posters)

Sunday, 9 October 2022
9:00 AM - 1:00 PM
Exhibit Hall F

RECONCILIATION OF PENNSYLVANIAN STRATIGRAPHIC NOMENCLATURE IN THE MIDCONTINENT, USA

Paper number: T30-6
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

The harmonization of Pennsylvanian stratigraphic nomenclature in the Midcontinent of the US (KS, OK, MO, NE, IA) has been hindered by the varied establishment of formal units by individual states. To come to a unified understanding of Pennsylvanian stratigraphy, a regional working group was created. Here we report working group findings from stratigraphic analysis of the upper Desmoinesian and lower Missourian stages together with proposed nomenclatural revisions for this interval.

Extant stratigraphic nomenclature was developed primarily from outcrop studies. We improve upon these works by incorporating extensive subsurface petrophysical data, drillers logs, and new drill cores. We also re-evaluate the original outcrops. These data include a network of subsurface-to-outcrop petrophysical transvers sections that span 36 adjoining counties. We include over 160 type, principal, and neostratotype sections, spanning 452 miles (~727 km; >120 located in Kansas) from Seminole County, OK, to Appanoose County, IA. Sixteen group and subgroup boundary-defining units were assessed as well as 10 proximal type sections. Together, these data revealed numerous discrepancies in previous correlations.

We proposed significant changes in stratigraphic nomenclature. The Pleasanton Group is demoted in rank to formation and included within the redefined Marmaton Group (MG). The lower boundary of the MG is established at the base of an unnamed limestone that immediately underlies the Excello Shale Member. The redefined MG comprises the Fort Scott, Appanoose/Oologah, and Holdenville subgroups. These subgroups, as presently used by individual states, are either raised in rank or have boundaries extended or restricted to coincide with regionally mappable units, and honor seniority. The Fort Scott Subgroup now includes the Little Osage Formation (raised in rank) and Labette Formation. The Appanoose/Oologah Subgroup includes the Pawnee, Bandera, and Altamont formations. The Holdenville Subgroup includes the Nowata, Lenapah, Memorial, and Pleasanton formations. Due to an inability to map regional boundaries between the Lost Branch, Shale Hill, and Hepler lithostratigraphic units, these units are demoted to members of a redefined Pleasanton Formation and will be retained on a state-by-state basis.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-382965

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