Characterization and stratigraphic review of the upper Jurassic – Lower Cretaceous Mendoza Group in the Blanco river valley (∼33°SL)

MOREL, LUCIANO; FENNELL, LUCAS M.; NAIPAUER, MAXIMILIANO; PÉREZ FRASETTE, MAXIMILIANO; FOLGUERA, ANDRÉS

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2023

0895-9811

The Jurassic-Cretaceous Mendoza Group is one of the most distinctive lithostratigraphic units of the widely surveyedNeuquén basin. This work focuses on its development in the Aconcagua basin, which crops out at theAconcagua fold-and-thrust belt in the Principal Cordillera, and contrasts with its evolution in the main Neuquénbasin by remarkable differences. By logging a series of stratigraphic sections, we performed a detailed revision ofthe Mendoza Group´s stratigraphy and contact relations along the Blanco River valley (∼33°S). We reassignedseveral outcrops to the Mendoza Group based on our field observations and recent research, updating the currentgeological map of the study area. We identified an irregular development of the lower contact relation with theAuquilco Formation that denotes the existence of a paleo-topography at the time of deposition of the upper bedsof the Mendoza Group. Moreover, we dismissed previous proposals of a lateral interfingering relation with theJuncal Formation, and in place, we describe an angular unconformity with an overlying Upper Miocene volcanicunit. Additional insight from the redefinition of the upper contact is brought by the characterization of an erosivesurface at the top of the Mendoza Group, and the identification of a period of subaerial platform exposition anderosion. A previous paleogeographical model shows a good fit with the observed facies along the Blanco Rivervalley and can be extended towards southern latitudes. Differences in the development of the Mendoza Group inthe Aconcagua basin and the main Neuquén basin have been acknowledged, and a potential origin of this unusualbehavior has been explored in the reactivation of an Early Jurassic structural high.