Moulton Formation

Moulton Formation
Name	Moulton Formation
Type	Geological formation
Period	Permian
Lithology	Sandstone, shale, limestone
Namedfor	Moulton, Iowa
Region	Midwestern United States
Country	United States

Moulton Formation The Moulton Formation is a Permian stratigraphic unit exposed in the Midwestern United States, notable for its siliciclastic and carbonate succession and for yielding marine and terrestrial fossils. It has been examined by regional geologists and paleontologists from institutions such as the United States Geological Survey, University of Iowa, Iowa Geological Survey, and referenced in broader syntheses by scholars affiliated with Smithsonian Institution, American Museum of Natural History, and Paleontological Society. The unit forms part of the Permian record that is correlated with sequences studied in contemporaneous basins like the Anadarko Basin, Midcontinent Rift, and exposures in Kansas and Oklahoma.

Overview

The Moulton Formation crops out primarily near Moulton, Iowa and nearby counties, lying within the broader physiographic provinces influenced by the Cedar River drainage and the Iowan Surface. Regional mapping by the Iowa Geological Survey and the United States Geological Survey places the unit between well-known formations that have been compared to sections in Kansas, Nebraska, and Illinois. Field studies have involved researchers from University of Nebraska–Lincoln, Iowa State University, University of Kansas, and consulting geologists from firms with contracts with the US Department of the Interior and the National Park Service for regional resource assessments.

Geology and Lithology

Lithologically, the Moulton Formation comprises interbedded sandstones, shales, and thin limestones, showing siliciclastic input similar to beds described in the Council Grove Group and carbonate horizons comparable to the Chesterian Series in outcrops examined by teams associated with University of Missouri and Kansas Geological Survey. Petrographic and geochemical work has been undertaken using labs at the Geological Society of America-affiliated departments and facilities at Iowa State University and University of Iowa Hospitals and Clinics for sample preparation and isotopic analysis. Grain-size trends and mineral assemblages echo provenance signals traced to paleodrainage systems linked to the Ancestral Rocky Mountains and the Appalachian Orogeny uplift cycles recognized by researchers at Pennsylvania State University and University of Tennessee.

Stratigraphy and Age

Stratigraphically, the Moulton Formation occupies a position within the Permian succession established by chronostratigraphers working with the International Commission on Stratigraphy scales and correlated using conodont biostratigraphy and radiometric tie points calibrated with data from the U.S. Geological Survey and the Geological Society of America. Correlations have been proposed with Permian sections in the Permian Basin and the Midcontinent Platform, with age assignments refined by specialists from Stanford University and Massachusetts Institute of Technology employing detrital zircon U-Pb geochronology. Sequence stratigraphic interpretations reference sea-level curves developed by researchers associated with University of Texas at Austin and regional unconformities mapped in collaboration with the Iowa Geological Survey.

Paleontology

Fossil assemblages reported from the Moulton Formation include brachiopods, bivalves, gastropods, crinoid ossicles, and occasional vertebrate remains, documented by paleontologists affiliated with the University of Iowa, Smithsonian Institution, Field Museum of Natural History, and the Paleontological Research Institution. Microfossils such as conodont elements and foraminifera have been studied by teams from University of California, Berkeley and Yale University to assist biostratigraphic correlation. Trace fossils and plant fragments link to macrofloral records curated by museums including the American Museum of Natural History and the Royal Ontario Museum, and comparative work has drawn on faunal lists from Kansas Geological Survey and collections at Harvard University.

Depositional Environment and Paleoecology

Interpretations of depositional environments integrate sedimentologic data and fossil content to suggest shallow marine shelves, estuarine margins, and proximal deltaic settings influenced by fluctuating Permian sea levels identified in global syntheses by the International Union of Geological Sciences and sea-level studies from University of California, Santa Cruz. Paleoecological reconstructions have been advanced by researchers at Cornell University and Ohio State University, proposing communities dominated by suspension feeders and opportunistic benthos, with episodic terrestrial input reflected in palynological work conducted with laboratories at Michigan State University and Rutgers University.

Economic Importance and Uses

Although not a major hydrocarbon reservoir like the Permian Basin, the Moulton Formation has been assessed for aggregate resources, shallow groundwater aquifers, and local cement raw material potential by state surveys and consultants tied to the Iowa Department of Transportation and the U.S. Environmental Protection Agency regional offices. Engineering geology studies involving Federal Highway Administration standards have evaluated its suitability for roadbed and construction fill in projects coordinated with Iowa DOT and county governments. Paleontological and stratigraphic data have also contributed to regional mineral exploration models used by companies working in the Midcontinent.

Category:Permian geology Category:Geologic formations of Iowa