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Stratigraphy and depositional history of the Aguja Formation (Upper Cretaceous, Campanian) of West Texas, southwestern USA

Thomas M. Lehman, Steven L. Wick, Craig C. Macon, Jonathan R. Wagner, Karen J. Waggoner, Alyson A. Brink and Thomas A. Shiller
Stratigraphy and depositional history of the Aguja Formation (Upper Cretaceous, Campanian) of West Texas, southwestern USA
Geosphere (Boulder, CO) (March 2024) Pre-Issue Publication

Abstract

Although the Aguja Formation (West Texas, southwestern USA) and its fossil vertebrate fauna have been known for over a century, its basic stratigraphic requisites (type area and type section) have not been formally documented. The formation is herein subdivided into a series of formal members, and a lectostratotype section is proposed. Lithostratigraphic and biostratigraphic subdivisions are documented and integrated with geochronologic data to provide an age model for the formation. Four terrestrial vertebrate biozones are proposed. There are at least four major depositional intervals represented in the Aguja and intertonguing Pen Formations. An initial progradational deltaic succession is recorded by the La Basa Sandstone and lower part of the Abajo Shale Members of the Aguja Formation. A second phase of deposition resulted in a retrogradational shoreface succession that includes the upper part of the Abajo Shale, overlying Rattlesnake Mountain Sandstone Member, and lower part of the McKinney Springs Tongue of the Pen Formation, up to a skeletal phosphate bed interpreted to represent the maximum flooding surface. The third phase of deposition comprises a progradational deltaic succession that includes the upper part of the McKinney Springs Tongue, Terlingua Creek Sandstone Member of the Aguja Formation, and lower part of the Alto Shale Member of the Aguja Formation. This third succession records eastward migration of the strandline and withdrawal of the Western Interior Seaway from the Big Bend region. The fourth phase of deposition comprises a series of aggradational fluvial channel and floodplain successions that form the upper part of the Alto Shale Member and is coincident with redirection of stream flow to the southeast. This interval is much thicker in the central part of the Big Bend region, thins to the southwest and northeast, and likely records initial subsidence in the Laramide Tornillo Basin. The upper part of this succession was also contemporaneous with a series of basaltic pyroclastic eruptions, the westernmost expression of the Balcones igneous province. A dramatic constriction in the southern entrance to the Western Interior Seaway through the Gulf of Mexico occurred during this final phase in deposition of the Aguja Formation and corresponds to a shift of stream flow southeastward and to an outbreak of local pyroclastic eruptions. Regional uplift associated with this episode of magmatism is likely responsible for closing the southern aperture of the Western Interior Seaway.


EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: Pre-Issue Publication
Title: Stratigraphy and depositional history of the Aguja Formation (Upper Cretaceous, Campanian) of West Texas, southwestern USA
Affiliation: Texas Tech University, Department of Geosciences, Lubbock, TX, United States
Published: 20240320
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 190
Accession Number: 2024-032206
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., strat. col., 1 table, geol. sketch map
N29°00'00" - N29°45'00", W103°30'00" - W103°15'00"
Secondary Affiliation: Texas Vertebrate Paleontology Collections, USA, United StatesBullock, Bennett & Associates, USA, United StatesUniversity of Southern Mississippi, USA, United StatesSul Ross State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2024, 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: 2024
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