Sedimentology, palaeontology, biostratigraphy and correlation of the Late Cretaceous Vilquechico Group of southern Peru

Abstract

Detailed analysis of the Late Cretaceous Vilquechico Group (formerly Vilquechico Formation) of the Southern Andes allows the recognition of three major sedimentary sequences, defining Lower, Middle and Upper Vilquechico lithologic formations (LVF, MVF and UVF respectively). Some of them (MVF and UVF) include in turn minor sedimentary sequences. In addition to dinosaur trackways, they contain a marine fauna (selachians, actinopterygians, molluscs) in their transgressive basal parts, and lacustrine fossils (charophytes, ostracods, gastropods) in their regressive continental upper parts. Two charophyte biozones characterize the MVF and the UVF respectively. The lithologic and sedimentary features of the major sequences, as well as their palaeontological contents allow large-scale correlations with other Andean series. Such correlations permit us to tentatively ascribe the unfossiliferous LVF to the Coniacian-early Santonian (?) time-span, and the MVF to the Santonian late Campanian interval. The UVF is of latest Campanian-late Maastrichtian age. As a consequence, the assumed correlations between the Vilquechico Group and some of the vertebrate-bearing Andean localities are revised.