Análisis estratigráfico y paleoambiental del Ordovícico Inferior (Formaciones Acoite y Sepulturas) al oeste de Purmamarca, Cordillera Oriental argentina

ASTINI, R.A.; WAISFELD, B.G,

Mendoza

Congreso; XII Congreso Geológico Argentino y II Congreso de Exploración de Hidrocarburos; 1993

The Acoite and Sepulturas Formation wich crop out in the western side of the Cordillera Oriental, in northwester Argentina, permit the examination of the depositional enviroments during the lower Ordovician in the region. The Acoite Formation consistS of several upward-thickening and coarsening siliciclastic marine cycles deposited in an increasingly shallow shelfenviroment, indicative of an active prograding shoreline. The high sediment rates, spectrum of facies and the abundance of wave-formed features (HCS-SCS and wave ripples) allow to relate it with wave, storm-dominated deltaic system, Successive shoaling sequences comparable to a parasequences sets imply relatively frequent progradation of the deltaic system, caused by relative sea level changes. The Sepulturas Formation represents the upper most associations in which distributary channels and interdistributary fines show evidences of tidaly controled sedimentation. These facies association is considered to be the final prograding stage before a sea-level drop. Finally, a regional correlation with similar sequences otucropping in the Famatina Range is suggested. This allows us to settle probable causes for the different depositional system built on the western margin of Gondwana for Arening to Llanvirn times, assuming their autochthony.