Stratigraphy of the El Jarillal Member (Chiquimil Formation, Upper Miocene), Sierra de Hualfin, province of Catamarca (Argentina)

Abstract

?Stratigraphy of the El Jarillal Member (Chiquimil Formation, Upper Miocene), Sierra de Hualfin, province of Catamarca (Argentina)?. El Jarillal Member is the upper member of the Chiquimil Formation in the surrounding area of Hualfin Range, which has an important fossil mammal association of Huayqueriense age (Late Miocene). This member is made up of a fining upward succession (760 m thick), with laminated fine-grained sandstones and interbedded fine conglomerates and coarse sandstones; the finer-grained facies prevail in the upper half of the member, with laterally continuous, tabular beds (Rio Villavil section). Facies analysis provided elements to define low-sinuosity graveled channel systems interbedded with sandy sheetflood deposits, continuing to the upper section in a playa lake or a muddy alluvial floodplain, with scarce slope. Latter bears the most vertebrate fossil fauna.

El Durazno section (900m thick) presents a coarser succession of conglomeradic lens, with tangential and trough-cross stratification. This section represents distal alluvial fan sedimentation with progradation to more proximal facies in the upper part of the member.

Both sections are included in the Hualfin depocentre into the Santa María-Hualfin Basin. Five tectosedimentary stages were defined in this basin: the first three include rifting processes and two stages of tectonic inversion. El Jarillal Member belongs to the third rifting stage.