Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina

The Lower Cretaceous Chachao Formation in the Malargüe anticline area consists of wackestone, packstone, and minor grainstone and mudstone rich in benthic fauna which were deposited in a shallow carbonate ramp. These shell beds are composed of a low-diversity molluscan fauna mostly dominated by oyst...

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Autores principales: Palma, R.M., Lanés, S.G.
Formato: JOUR
Materias:
Cretaceous
depositional environment
paleoenvironment
shell bed
stratigraphy
taphonomy
Argentina
Mendoza Province
Neuquen Basin
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_08912556_v16_n2_p168_Palma
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_08912556_v16_n2_p168_Palma2023-10-03T15:41:17Z Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina Palma, R.M. Lanés, S.G. Cretaceous depositional environment paleoenvironment shell bed stratigraphy taphonomy Argentina Mendoza Province Neuquen Basin The Lower Cretaceous Chachao Formation in the Malargüe anticline area consists of wackestone, packstone, and minor grainstone and mudstone rich in benthic fauna which were deposited in a shallow carbonate ramp. These shell beds are composed of a low-diversity molluscan fauna mostly dominated by oysters, other benthic pelecypods (Eryphila sp., Ptychomya sp., Pecten sp., Pinna sp., Trigonia sp., Cucullaea sp.), serpulids (Sarcinella sp., Parsimonia sp.), and occasional ammonites (Olcosthepanus curacoensis). Most skeletal accumulations range from 15 to 70 cm in thickness. Shell beds exhibit a sharp, flat and commonly undulating base. In some cases the tops were bioturbated principally by Thalassinoides isp. Some shell beds show a densely packed biofabric (bioclastic-supported) but most of them have dispersed or loosely packed biofabric (mud-supported). Bioclasts include articulated or disarticulated shells, fragmented valves and shell debris. The analysis of shell concentrations of the Chachao Formation allow to recognize four taphofacies according to their taphonomic attributes. Different kind of processes, such as low-energy storm currents and waves, were interpreted, whose deposits are arranged into a coarsening- and thickening-upward and then fining- and thinning upward trends. According to their biostratinomic features shell beds of Chachao Formation have been interpreted as parautochthonous to autochthonous skeletal concentrations, mainly of sedimentologic origin. Towards the end of the Valanginian, the drowning of the carbonate ramp took place, related to a relative sea level rise and environmental stress. This drowning event was recorded by the alternating thin- to medium bedded dark gray carbonate and black shales (Agrio Formation) of Late Valanginian-Late Hauterivian age. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_08912556_v16_n2_p168_Palma
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Cretaceous
depositional environment
paleoenvironment
shell bed
stratigraphy
taphonomy
Argentina
Mendoza Province
Neuquen Basin
spellingShingle Cretaceous
depositional environment
paleoenvironment
shell bed
stratigraphy
taphonomy
Argentina
Mendoza Province
Neuquen Basin
Palma, R.M.
Lanés, S.G.
Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina
topic_facet Cretaceous
depositional environment
paleoenvironment
shell bed
stratigraphy
taphonomy
Argentina
Mendoza Province
Neuquen Basin
description The Lower Cretaceous Chachao Formation in the Malargüe anticline area consists of wackestone, packstone, and minor grainstone and mudstone rich in benthic fauna which were deposited in a shallow carbonate ramp. These shell beds are composed of a low-diversity molluscan fauna mostly dominated by oysters, other benthic pelecypods (Eryphila sp., Ptychomya sp., Pecten sp., Pinna sp., Trigonia sp., Cucullaea sp.), serpulids (Sarcinella sp., Parsimonia sp.), and occasional ammonites (Olcosthepanus curacoensis). Most skeletal accumulations range from 15 to 70 cm in thickness. Shell beds exhibit a sharp, flat and commonly undulating base. In some cases the tops were bioturbated principally by Thalassinoides isp. Some shell beds show a densely packed biofabric (bioclastic-supported) but most of them have dispersed or loosely packed biofabric (mud-supported). Bioclasts include articulated or disarticulated shells, fragmented valves and shell debris. The analysis of shell concentrations of the Chachao Formation allow to recognize four taphofacies according to their taphonomic attributes. Different kind of processes, such as low-energy storm currents and waves, were interpreted, whose deposits are arranged into a coarsening- and thickening-upward and then fining- and thinning upward trends. According to their biostratinomic features shell beds of Chachao Formation have been interpreted as parautochthonous to autochthonous skeletal concentrations, mainly of sedimentologic origin. Towards the end of the Valanginian, the drowning of the carbonate ramp took place, related to a relative sea level rise and environmental stress. This drowning event was recorded by the alternating thin- to medium bedded dark gray carbonate and black shales (Agrio Formation) of Late Valanginian-Late Hauterivian age.
format JOUR
author Palma, R.M.
Lanés, S.G.
author_facet Palma, R.M.
Lanés, S.G.
author_sort Palma, R.M.
title Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina
title_short Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina
title_full Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina
title_fullStr Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina
title_full_unstemmed Shell bed stacking patterns in the Chachao formation (Early Valanginian) in Malargüe area, Mendoza Province, Neuquen Basin-Argentina
title_sort shell bed stacking patterns in the chachao formation (early valanginian) in malargüe area, mendoza province, neuquen basin-argentina
url http://hdl.handle.net/20.500.12110/paper_08912556_v16_n2_p168_Palma
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