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Evaporitic paleosols in continental strata of the Carroza Formation, La Popa Basin, Mexico; record of Paleogene climate and salt tectonics

Brenda J. Buck, Timothy F. Lawton and Amy L. Brock
Evaporitic paleosols in continental strata of the Carroza Formation, La Popa Basin, Mexico; record of Paleogene climate and salt tectonics
Geological Society of America Bulletin (July 2010) 122 (7-8): 1011-1026

Abstract

A succession of continental red beds in the Paleogene Carroza Formation, northeastern Mexico, contains an assemblage of evaporite paleosols previously unknown in pre-Neogene strata that record the syndepositional exposure of nearby diapiric evaporite and a climatic shift to increasing aridity. Carroza red beds were deposited in an ephemeral braided-fluvial system in a high-accommodation setting. Paleosols developed in nearly all depositional settings, including channels, crevasse splays, and floodplains, and contain salic/natric, gypsic, baritic, and calcic horizons. Calcic paleosols are limited stratigraphically to the lowermost part of the formation in oyster-bearing estuarine strata and yield upsection to evaporitic paleosols, thus providing a record of increasingly arid conditions as the Paleogene marine shoreline shifted eastward, toward the Gulf of Mexico Basin. The increase in aridity reduced vegetation and residuum thickness on the exposed diapiric salt, consequently increasing the influx of evaporitic minerals into the basin, and driving the development of salic/natric, gypsic, and baritic horizons in all depositional environments. Evaporitic paleosols of the Carroza Formation have characteristics similar to soils forming today in climates with annual precipitation ranging from <80 mm/yr to as much as 450 mm/yr, in apparent conflict with estimates of subhumid to subtropical conditions from Carroza fossil leaf data. Because evaporitic paleosols are persistent throughout the Carroza section, we infer that a combination of spring-fed, high water tables, augmented by flood-basin inundation from high-discharge seasonal fluvial flood events sustained perennial woodlands, and sodium-caused clay dispersion created poor drainage in topographically low parts of a rapidly subsiding salt-withdrawal basin.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 7-8
Title: Evaporitic paleosols in continental strata of the Carroza Formation, La Popa Basin, Mexico; record of Paleogene climate and salt tectonics
Affiliation: University of Nevada-Las Vegas, Department of Geoscience, Las Vegas, NV, United States
Pages: 1011-1026
Published: 201007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 75
Accession Number: 2010-050182
Categories: StratigraphySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2010040
Illustration Description: illus. incl. sects., geol. sketch maps
N25°55'00" - N26°19'60", W101°10'00" - W100°40'00"
Secondary Affiliation: New Mexico State University, USA, United StatesWestern Illinois University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, 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: 201027
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