Abstract

DEL HUERTO BENITEZ, María. Facial And Paleoenvironment Study Of The Coquena Formation (Upper Tremadocian) At The Purmamarca Region, Cordillera Oriental Of Jujuy. Ser. correl. geol. [online]. 2013, vol.29, n.2, pp.7-20. ISSN 1666-9479.

The upper Tremadocian Coquena Formation at the Chalala Creek (Purmamarca, northwestern Argentina) is a heterolithic dominantly sandy sequence. A 350 m thick section was relevated, its base is no exposed, while its top is unconformably covered by modern sediments. The succession is represented by fve sedimentary facies, which are dominated by sand sediments, showing wave-and current-structures, and subordinate shaly levels. The psamitic levels are composed of very fine to fine, greenish gray, very consistent sandstones. The geometry of these beds is tabular or lenticular characterized by having abundant bioclastic horizons. The finest material, present primarily in the lower to middle part of the profile, corresponds to greenish shales and sandy siltstones, highly alterated. The study of theses facies refect different subenvironments of platform affected by storms, firom middle shoreface to offshore, where the sandy material was transported and re-worked by numerous episodic events. The description and interpretation of these sedimentary facies in association with the biostratigraphic information available, allowed us understanding the sedimentary dynamic of the Ordovician shelf and correlate the Chalala Creek with the others localities of the Eastern Cordillera.

Keywords : Facies; Paleoenvironment; Coquena Formation; Upper Tremadocian.

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