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High frequency subtidal-peritidal cycles of the Callovian Calabozo Formation (Neuquén Basin, Western Argentina): preliminary approach
Palma, R.M. (Universidad de Buenos Aires. Departamento de Ciencias Geológicas)
Lo Forte, G.L. (UBA-CONICET. Departamento de Ciencias Geológicas)
Medhli, M. (Université Ibn Tofail. Department de Geologie)
Piethé, R.D. (Universidad de Buenos Aires. Departamento de Ciencias Geológicas)

Data: 2005
Resum: The Calabozo Formation (Cuyo Mesosequence, Neuquén Basin) is made up by a thin, up to 30-m thick Middle Jurassic carbonate-dominated sequence. The minor, thin siliciclastic facies in this formation (i. e. lowermost granule-pebble shoreface conglomerate and fine-grained sandstones interbedded among the lower carbonates) record early transgressive shoreline and shallow lagoonal-subtidal sedimentation, respectively. The major carbonate deposits have been split into six facies and seven microfacies on the base of macroscopic field observation and petrological analysis. The carbonate facies have been grouped into three major assemblages: 1) Tidal flat facies assemblage (including the planar laminated algal boundstone facies; 2) Inner platform facies assemblage (including peloidal and bioclastic wackestone, coral floatstone and bioclastic and intraclastic packstone facies; and 3) Platform margin assemblage (including oolitic-peloidal packstone-grainstone facies). Afossil algal record made up by dasycladacean species (Salpingoporella annulata, Cylindroporella sp. and Heteroporella sp. ) and blue-green algae (Cayeuxia (Rivularia) piae, and Cayeuxia (Rivularia) kurdistanensis) has been reported for the first time in this unit. The analysis of the intracycle facies and microfacies arrangements, as well as the nature of the cycle bounding surfaces, enabled one to identify two kinds of cycles. 1) Widespread subtidal cycles capped by shallow to intermediate subtidal facies, with no evidence of subaerial exposure at cycle tops; and 2) a minor subtidal cycle with similar shallowing-upward trend but capped by peritidal facies. The stacking pattern and thickness trend of these cycles was studied to determine possible allocyclic and autocyclic controls on their evolution. The Fischer plots reveal that the deposition of the Calabozo Formation subtidal-peritidal cycles took place under upward decreasing accommodation space conditions which may be related to eustatic lowering.
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Llengua: Anglès.
Document: article ; recerca ; publishedVersion
Matèria: Subtidal-Peritidal Cyclicity ; Carbonate facies and microfacies ; Jurassic
Publicat a: Geologica acta, Vol. 3, Núm. 2 (2005) , p. 119-132, ISSN 1696-5728

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DOI: 10.1344/105.000001401

14 p, 911.6 KB

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