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

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

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2023

0895-9811

The Jurassic-Cretaceous Mendoza Group is one of the most distinctivelithostratigraphic units of the widely surveyed Neuquén basin. This work focuses on itsdevelopment in the Aconcagua basin, which crops out at the Aconcagua fold-and-thrust beltin the Principal Cordillera, and contrasts with its evolution in the main Neuquén basin byremarkable differences. By logging a series of stratigraphic sections, we performed adetailed revision of the Mendoza Group’s stratigraphy and contact relations along the BlancoRiver valley (∼33°S). We reassigned several outcrops to the Mendoza Group based on ourfield observations and recent research, updating the current geological map of the studyarea. We identified an irregular development of the lower contact relation with the AuquilcoFormation that denotes the existence of a paleo-topography at the time of deposition of theupper beds of the Mendoza Group. Moreover, we dismissed previous proposals of a lateralinterfingering relation with the Juncal Formation, and in place, we describe an angularunconformity with an overlying Upper Miocene volcanic unit. Additional insight from theredefinition of the upper contact is brought by the characterization of an erosive surface atthe top of the Mendoza Group, and the identification of a period of subaerial platformexposition and erosion. A previous paleogeographical model shows a good fit with theobserved facies along the Blanco River valley and can be extended towards southernlatitudes. Differences in the development of the Mendoza Group in the Aconcagua basinand 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.