Moorefield Formation

Moorefield Formation
Name	Moorefield Formation
Type	Geological formation
Period	Mississippian
Prilithology	Shale, limestone
Otherlithology	Sandstone, siltstone
Region	Oklahoma, Arkansas, Kansas
Country	United States

Moorefield Formation

Introduction

The Moorefield Formation is a Mississippian stratigraphic unit recognized in Oklahoma, Arkansas, and parts of Kansas and the Ouachita Mountains. Its succession of shales, limestones, and subordinate sandstones preserves marine and nearshore records that have been studied by geologists from institutions such as the United States Geological Survey, University of Oklahoma, and Arkansas Geological Survey. Researchers including Charles DeFord, A. W. Grabau, and later workers associated with the American Association of Petroleum Geologists and the Society for Sedimentary Geology have mapped and correlated the unit with regional Mississippian stratigraphy.

Geologic Setting and Stratigraphy

The Moorefield Formation lies above the Chesterian Series equivalents and below Pennsylvanian units in parts of the mid-continent. It is commonly placed within the late Meramecian to early Chesterian interval of the Mississippian and shows lateral gradation into units recognized in the Ardmore Basin, Arkoma Basin, and the central Midcontinent Rift influence. Stratigraphic work by teams from the Pennsylvania Geological Survey, Kansas Geological Survey, and the Oklahoma Geological Survey has emphasized marker beds, biostratigraphy using conodonts and brachiopods, and correlation with classic sections studied near Fort Smith and Little Rock.

Lithology and Sedimentology

Lithologies in the Moorefield include dark, organic-rich shales, thin-bedded to nodular limestones, calcareous siltstones, and occasional bioclastic sandstones. Petrographic studies conducted at Massachusetts Institute of Technology and University of Kansas laboratories show micritic matrices, sparry calcite cement, and clay mineral assemblages similar to contemporaneous units described by researchers at Harvard University and the Smithsonian Institution. Sedimentologic features such as laminations, burrow traces, and storm beds have been compared with facies models developed by scholars affiliated with the International Association of Sedimentologists and the Geological Society of America.

Paleontology and Fossil Content

The Moorefield yields a diverse marine fossil assemblage including brachiopods, crinoids, bryozoans, bivalves, gastropods, cephalopods, trilobites, echinoderm fragments, and microfossils such as conodonts and foraminifera. Collections deposited in the National Museum of Natural History, University of Arkansas Museum of Paleontology, and Sam Noble Museum include taxa comparable to those described by paleontologists from Yale University and the University of Chicago. Biostratigraphic work using conodont zones and ammonoid correlations has been informed by regional faunal lists published in journals like Palaeontology and Journal of Paleontology.

Age and Correlation

Radiometric and biostratigraphic constraints place the Moorefield within the middle to late Mississippian (approximately the Visean–Serpukhovian interval in global chronostratigraphy). Correlations have been drawn with European Mississippian basins studied by researchers at University of Cambridge and Imperial College London, and with North American units such as the Greenbrier Formation and the Chesterian Series. International correlation frameworks used by the International Commission on Stratigraphy and comparative charts from the Paleobiology Database assist in placing the Moorefield in a global context.

Depositional Environment and Paleogeography

Sedimentological and paleontological evidence indicates deposition in a shallow epicontinental sea influenced by eustatic changes and regional tectonics associated with the late Paleozoic evolution of the Laurentia craton. Paleogeographic reconstructions by teams from Purdue University, University of Texas at Austin, and the University of Colorado Boulder depict the region as a broad shelf with episodic siliciclastic influx from highlands related to deformational events in the Ouachita Orogeny and accommodation controlled in part by sea-level fluctuations recognized in sequences correlated with work from the Stratigraphy Commission and the International Geoscience Programme.

Economic Resources and Uses

The Moorefield Formation has been evaluated for hydrocarbon potential, shale gas, and as a source-rock candidate by energy companies and researchers at the Energy Information Administration and the Bureau of Land Management. Its organic-rich shales have been compared with productive intervals in the Appalachian Basin and Anadarko Basin in assessments published by the American Chemical Society and industry partners. Locally, limestone beds have been quarried for aggregate and construction purposes, with studies by the Federal Highway Administration and state transportation departments documenting use in infrastructure projects.

Category:Geologic formations of the United States Category:Mississippian geology Category:Stratigraphy