Conodontes de la Formación Las Chacritas (Darriwilliano) y su significado tecto-sedimentario en el bloque de la Sierra de La Trampa-Los Blanquitos, Precordillera de San Juan

HEREDIA, S.; ROSALES, C.V.; PERALTA, S.H.; BERESI, M.S.

La Plata

Congreso; XVI Congreso Geológico Argentino; 2005

Asociación Geológica Argentina

Las Chacritas Formation in the type section at the Sierra de La Trampa, Central Precordillera (San Juan Province) was deposited in an outer carbonate ramp setting that evolved from relatively deep to shallow water. Samples from this well-exposed Middle Ordovician section yielded collections of low-diversity conodont faunas stratigraphically significant. The top of the underlying San Juan Formation and the lower and middle parts of the Las Chacritas Formation contain conodonts representative of the Lenodus variabilis Zone, and the upper part of the Las Chacritas Formation yields to the top the Paroistodus horridus subzone of the upper part of the Lenodus variabilis Zone, Eoplacognathus pseudoplanus/Dzikodus tablepointensis Zone, and Eoplacognathus suecicus Zone.  Conodont biofacies are analyzed trough the entire section, and they support a regressive event to the top.  A forced regressive event is stated, controlled by uplifting of the Sierra de La Trampa-Los Blanquitos structural belt placed in the Central Precordillera.