Mineralogical and geochemical analyses of the Vaca Muerta-Quintuco system (Tithonian-Valanginian) in the Chacay Melehue area, Neuquén Basin, Argentina

CAPELLI, I.; ADATTE, T.; FOLLMI, K.; SCASSO, R.A.; KIETZMANN, D.A.; REUBI, O.; CRAVERO, M.F.; CATALANO, J.P.

Congreso; 27th Meeting of Swiss Sedimentologists; 2019

The Vaca Muerta-Quintuco system is an organic-rich, marine, shale succession deposited during the Tithonian-Valanginian in the Neuquén Basin, western Argentina. During that time, the basin was a semi-restricted back-arc basin, located to the east of a volcanic-arc and periodically flooded by the Paleopacific Ocean (e.g., Legarreta and Uliana 1996).The Vaca Muerta Formation constitutes an outstanding unconventional oil and gas reservoir, and has received worldwide attention during the last decade, because of its high organic matter content (up to 12 %, average 4 %) and its exceptional petrophysics properties.The Vaca Muerta-Quintuco system is 884 m thick in the well-exposed surface section of Chacay Melehue, located in the northern part of the basin. The basal deposits are characterized by basinal facies of the Vaca Muerta Formation (carbonate ramp), progressively covered by pro-deltaic/offshore deposits of the Quintuco Formation (see Kietzmann et al. 2016, Capelli et al. 2018).50 samples of the Chacay Melehue section were analysed to determine major and trace elements, bulk and clay mineralogy, as well as organic matter content (TOC) and maturity. This mineralogical and geochemical study, with special focus on organic matter accumulation and detrital input shows how the sedimentary environment changed, allowing us to infer major paleoclimatic changes through the Tithonian-Valanginian.