Carboniferous outcrops at La Herradura Creek, San Juan Province (Western Argentina), revisited: age of the transgressions

PEREZ LOINAZE, V.; C.O. LIMARINO,; CÉSARI, S.

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Lugar: Santiago de Chile; Año: 2014 vol. 41 p. 83 - 105

0718-7092

ABSTRACT. At the outcrops of the Tupe Formation in the La Herradura Creek, San Juan Province, two transgressiveevents are recorded, which range from few meters to tens of meters in thickness. These strata correspond to the stratotypeof the faunal Tivertonia jachalensis-Streptorhynchus inaequiornatus Biozone. An evaluation of the timing of the twomarine transgressions is made on the basis of palynological assemblages and available radiometric ages. A short-livedtransgression is recorded in the latest Bashkirian-early Moscovian, and then a substantial sea level fall took place formingan irregular incision surface. Later, a major high eustatic sea-level occurred during the middle Moscovian resulting in amore important marine ingression. The palynological assemblages associated to the older transgressive event indicatethe presence of the Raistrickia densa-Convolutispora muriornata (DM) Biozone (Subzone B). Palynofloras referred tothe Subzone C of the DM Biozone characterize the strata of the younger transgression that also bear marine fauna ofthe Tivertonia jachalensis-Streptorhynchus inaequiornatus Biozone. Correlations with other Pennsylvanian outcrops inthe region give support to the stratigraphic scheme here proposed.