Abstract

DEL HUERTO BENITEZ, María. Depósitos de Tormenta en la Formación Coquena (Tremadociano superior) de la Quebrada de Chalala, Cordillera Oriental jujeña. Rev. Asoc. Geol. Argent. [online]. 2013, vol.70, n.2, pp.183-192. ISSN 0004-4822.

The Upper Tremadocian Coquena Formation at the Chalala Creek (Purmamarca, northwestern Argentina) is a heterolithic dominantly sandy sequence that is characterized by having abundant bioclastic horizons. It is represented by five sedimentary facies, which are dominated by sandstones, showing wave-and current- generated structures, and subordinate pelitic levels. These facies reflect different subenvironments of a platform affected by storms, from middle shoreface to upper offshore, where the sandy material was transported and re-worked by numerous episodic events. Proximal amalgamated, proximal nonamalgamated and distal tempestites were recognized in the succession. Proximal amalgamated storm deposits are characterized by their sandy beds with hummocky cross stratification, basal bioclastic horizons and erosional tops, without any intervening pelitic layer. Proximal non-amalgamated storm deposits are represented by thick sandy beds with hummocky cross stratification, bioclastic accumulations and ripples at the top intercalated with thin shaly levels. Distal storm deposits are laminated o silty to sandy beds intercalated in shaly intervals.

Keywords : Tempestites; Storms; Coquena Formation; Ordovician; Shelf.

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