New dinoflagellate cyst records from the uppermost part of the Vaca Muerta Formation (uppermost Jurassic) in the Picún Leufú area, Neuquén Basin, Patagonia, Argentina

Abstract

This contribution presents a new palynological record from the uppermost Vaca Muerta Formation in the Picún Leufú area, Neuquén Basin, Argentina. A 76 m section was measured, and seven mudstone samples from the top of the Vaca Muerta Formation and the base of the Picún Leufú Formation were collected. Seventy-three palynomorph species were recognised and specimens of the dinoflagellate cyst genera Dingodinium, Gochteodinia, Ambonosphaera, Diacanthum, Systematophora, Tubotuberella, Wrevittia and Canningia were described and illustrated. The following taxa are mentioned for the first time: Tubotuberella in the Vaca Muerta Formation; Gochteodinia in Argentina; and Wrevittia in the Jurassic of Argentina. The dinoflagellate cyst content, integrated with previous studies, constrain the top of the Vaca Muerta Formation in the southern part of the basin, to the lower upper Tithonian. This study extends the basal limit of Pseudoceratium notiale to the lower upper Tithonian and Cribroperidinium reticulatum to the Tithonian. From a paleobiogeographic perspective, the presence of Thalassiphora robusta could provide evidence of its migration from the Volga Basin. Besides, taxa shared with the Tithonian of southeast Tanzania could be reflecting the connection between the Neuquén and the Mandawa basins via the Mozambique Corridor. The dinoflagellate cyst content of the uppermost Vaca Muerta Formation shows a relative decrease in previously reported species for this unit approaching the formational contact, alongside an increase in those species previously documented for the Picún Leufú Formation. The distribution of Pseudoceratium notiale, Dichadogonyaulax culmula and Pilosidinium cactosum was extended to the uppermost Vaca Muerta Formation.