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Recognition of fossil nebkha deposits; clues from neoichnology and sedimentology

M. Cristina Cardonatto and Ricardo Nestor Melchor
Recognition of fossil nebkha deposits; clues from neoichnology and sedimentology
Palaios (July 2020) 35 (7): 277-291

Abstract

This study includes the first neoichnologic characterization of the burrow systems of Tympanoctomys barrerae (Rodentia: Octodontidae) and also considers sedimentologic features of the modern nebkhas where they occur. Tympanoctomys is a South American solitary and fossorial rodent that has ecomorphofunctional adaptations for living in saline environments and constructs its burrow in nebkhas with halophyte shrubs. The purpose of this work is to identify the ichnologic signatures of T. barrerae burrow systems and to provide combined ichnologic-sedimentologic criteria for identification of Cenozoic nebkha deposits. Tympanoctomys barrerae burrow systems are subhorizontal, typically with ten or more entrances, two or three levels, closed circuits, average complexity of 48, average tortuosity of 3.25, and an average ratio of total chamber volume to total tunnel volume of 0.04. The size of the tunnels averages 85 mm in horizontal diameter and 64 mm in vertical diameter, and cross-section shape ranges from elliptical flattened to plano-convex with incipient bilobed floor. Surface ornamentation is typified by a coexistence of primary (sets of four claw traces forming an arcuate pattern produced during digging) and secondary (numerous arthropod burrows excavated from the burrow lumen) surface ornamentation. Nebkha deposits in upper Cenozoic sequences can be recognized by the combination of ichnologic and sedimentologic features: fossil burrows having the ichnologic features characteristic of T. barrerae burrow systems and presence of rhizoliths of shrubby plants occurring in well-sorted sandy deposits with low-angle crossbedding. These criteria can be potentially applied to fossil sequences dating back to the early Oligocene.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 35
Serial Issue: 7
Title: Recognition of fossil nebkha deposits; clues from neoichnology and sedimentology
Affiliation: Universidad Nacional de La Pampa, Departamento de Geologia, Santa Rosa, Argentina
Pages: 277-291
Published: 202007
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 83
Accession Number: 2021-006440
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 1 plate, 1 table, geol. sketch map
S37°23'60" - S37°23'60", W67°13'00" - W67°13'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 202105
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