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Early Paleocene magnetostratigraphy and revised biostratigraphy of the Ojo Alamo Sandstone and lower Nacimiento Formation, San Juan Basin, New Mexico, USA

Andrew G. Flynn, Adam J. Davis, Thomas E. Williamson, Matthew Heizler, C. William Fenley, Caitlin E. Leslie, Ross Secord, Stephen L. Brusatte and Daniel J. Peppe
Early Paleocene magnetostratigraphy and revised biostratigraphy of the Ojo Alamo Sandstone and lower Nacimiento Formation, San Juan Basin, New Mexico, USA
Geological Society of America Bulletin (March 2020) Pre-Issue Publication

Abstract

The lower Paleocene Ojo Alamo Sandstone and Nacimiento Formation from the San Juan Basin (SJB) in northwestern New Mexico preserve arguably the best early Paleocene mammalian record in North America and is the type location for the Puercan (Pu) and Torrejonian (To) North American land mammal ages (NALMA). However, the lack of precise depositional age constraints for the Ojo Alamo Sandstone and lower Nacimiento Formation has hindered our understanding of the timing and pacing of mammalian community change in the SJB following the Cretaceous-Paleogene mass extinction. Here we produced a high-resolution age model for the Ojo Alamo Sandstone and lower Nacimiento Formation combining magnetostratigraphy and (super 40) Ar/ (super 39) Ar geochronology spanning the first approximately 3.5 m.y. of the Paleocene. Mean sediment accumulation rates during C29n were relatively low (<50 m/m.y.) and equalized from basin center to basin margin indicating an accommodation minimum; sediment accumulation rates approximately double (>90 m/m.y.) during C28r and are highest in the basin center and lowest on basin margin, which indicates high accommodation and an increase in basin subsidence near the C29n/C28r boundary (ca. 64.96 Ma). Puercan fossil localities were restricted to C29n, Torrejonian 1 localities to C28n, and lower Torrejonian 2 localities to C27r. Our revised age model for the SJB suggests that the first appearance of To1 mammals may have been diachronous across North America, with the Torrejonian 1 mammals first appearing in the north (Montana and North Dakota) during C29n, then in middle latitudes (Utah) in C28r, and lastly in southern North America (New Mexico) in C28n.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: Pre-Issue Publication
Title: Early Paleocene magnetostratigraphy and revised biostratigraphy of the Ojo Alamo Sandstone and lower Nacimiento Formation, San Juan Basin, New Mexico, USA
Affiliation: Baylor University, Department of Geosciences, Waco, TX, United States
Published: 20200310
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 84
Accession Number: 2020-028721
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository iten 2020127
Illustration Description: illus. incl. 5 tables, geol. sketch map
N36°00'00" - N37°00'00", W108°30'00" - W107°00'00"
Secondary Affiliation: New Mexico Museum of Natural History and Science, USA, United StatesNew Mexico Bureau of Geology & Mineral Resources, USA, United StatesUniversity of Nebraska-Lincoln, USA, United StatesUniversity of Edinburgh, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202009
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