JURASSIC ORGANIC-WALLED MARINE MICROPLANKTON FROM THE NEUQUÉN BASIN. DISTRIBUTION, BIOSTRATIGRAPHY AND PAlEOBIOGEOGRAPHY. A REVIEW

MARTÍNEZ, MARCELO A.; OLIVERA, DANIELA

Publicacion Electrónica de la Asociación Paleontológica Argentina

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2016 vol. 16 p. 106 - 128

2469-0228

The Mesozoic era is crucial for analyzing the replacement of microplanktonic lineages resulting from the beginning of the break-upof Pangea. The paleogeography of south America, and hence of Argentina, underwent successive changes since this time. The opening ofdifferent seaways, mainly during the Jurassic, affected the global circulation pattern of the oceans which determined the composition of theorganic-walled marine microplankton associations of the Neuquén Basin. These Jurassic marine palynofloras are summarized here, based onthe information from outcrop samples of 12 units, which were analyzed from a paleobiogeographic point of view. The configuration of thebasin during the early Jurassic was characterized mainly by partially interconnected depocenters, with restricted marine circulation that favoredthe development of associations dominated by components of the green lineage (acritarchs and prasinophytes). The Cuyo and lotenagroups (Middle Jurassic) were accumulated during two important flooding episodes which generated the paleoecological conditions for anincrease in the diversity of the red lineage (dinocysts). since the late Callovian the hispanic Corridor connected the Neuquén Basin with theTethyan realm allowing the free interchange of species. The late Jurassic marine palynofloras are best characterized in the Vaca Muertaand Picún leufú formations. The anoxic condition that prevailed during the accumulation of the Vaca Muerta formation marked the return tothe dominance of the green lineage. Conversely, the Picún leufú formation represents neritic more oxygenated bottom waters that favoreda relative increase in the abundance and diversity of dinoflagellate cysts.