Correlation of late Cenozoic sequences of southeastern Buenos Aires province: Biostratigraphy and magnetostratigraphy

Abstract

Correlations among stratigraphic sequences of the continental late Cenozoic of southeastern Buenos Aires province have been historically based on lithostratigraphy and paleontological content. Recent magnetostratigraphic studies supplied new evidence which, together with biostratigraphy, allowed improvement of the chronostratigraphic framework. Recent studies were conducted at four localities of southeastern Buenos Aires province: Playa Santa Elena, Punta Hermengo, Mar del Sur and Centinela del Mar. The studied sequences at Santa Elena and Mar del Sur show normal magnetic polarity, while Punta Hermengo and Centinela del Mar display levels of reverse polarity. Discontinuities in the sequence of Mar del Sur might explain the absence of sediments of reverse polarity. Thus, some units (the lower ones) could correspond to the normal magnetic events C1r1n and/or C2n, as the fossil fauna collected here has no typical Pliocene components that could suggest an age older than the Gauss?Matuyama boundary (i.e., >2.58 Ma). The basal levels of the profile at Punta Hermengo, with reverse polarity, display Ensenadan fauna. This may be the most recent section of C1r (C1r1r, 0.90?0.78 Ma), which took place after the normal Jaramillo event (C1r1n). The lower unit of Playa Santa Elena, of normal polarity (C1n), bears mammal remains suggesting a late Ensenadan age (<0.78 Ma). The base of the Centinela del Mar sequence that shows reverse polarity levels and bears bones of mammals probably is of undifferentiated Pleistocene age.