Early-middle Darriwilian graptolite and conodont faunas from the central Precordillera of San Juan Province, Argentina

SERRA F.; FELTES N.A.; ORTEGA, G.; ALBANESI G.L

Harrisonburg

Simposio; 12th International Symposium on the Ordovician System; 2015

IUGS UNESCO

The Precordillera of western Argentina is characterized by lower Paleozoic carbonate rocks, whichincludes conspicuous Lower-Middle Ordovician deposits overlain by Middle-Upper Ordovician blackshales involving a hiatus related to the global Sandbian transgressive event. The relative dating of theunits indicate a diachronous deposition of the succession, which begins in the upper Dapingian(Isograptus maximus Zone) in the north and ranges to the lower Darriwilian (Levisograptusdentatus Zone) in the south. The study sections from the Central Precordillera of San Juan Province,located to the south west and north east of Jáchal City, involve the Las Aguaditas Creek, Las ChacritasRiver, Oculta Creek, Potrerillo Hill and La Chilca Hill (Figure 1A). In the Jáchal area, the OrdovicianSystem is extensively represented and has been the subject of many paleontological and geologicalstudies (references in Albanesi et al. 2013).The present contribution deals with early Darriwilian graptolites and index conodonts recorded from unitsthat overlie the calcareous San Juan Formation (upper Tremadocian-lower Darriwilian), spanning thelower part of the Las Aguaditas, Gualcamayo and Los Azules formations, and the Las ChacritasFormation in their respective areas.