Sedimentology and sequence stratigraphy of a Tithonian-Valanginian carbonate ramp (Vaca Muerta Formation): a misunderstood exceptional source rock in the Nuequen Basin, Argentina

KIETZMANN, D.A., PALMA, R.M., RICCARDI, A.C., MARTIN-CHIVELET, J., LOPEZ-GOMEZ, J.

SEDIMENTARY GEOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 302 p. 64 - 86

0037-0738

The Vaca Muerta Formation (early Tithonian - early Valanginian) is a rhythmic succession of marls and limestones, outcropping in the southern Mendoza sector of the Neuquén Basin, west-central Argentina. This lithostratigraphic unit was traditionally interpreted as basinal to slope deposits. Detailed facies analysis allows to differentiate seven facies association, which represent basinal to middle ramp facies of an homoclinal ramp system that prograde westward from the eastern margin, and slope facies attributed to a distally steepened ramp system that prograde to the eastward from the Andean volcanic arc in the west. Sequence stratigraphic framework is defined using the trangressive-regressive model, due to lack of subaerial exposure evidences, and the excellent development of flooding surfaces. Two hierarchies of trangressive-regressive cycles are recognized, four large scale transgressive-regressive cycles, and ten small scale depositional sequences. First transgressive-regressive cycle TR-1 starts in the lower Tithonian (Virgatosphinctes mendozanus Biozone) with a regional flooding surface, which overlap late Kimmeridgian continental/transitional deposits by microbialite dominated outer ramp deposits, and ends in the uppermost middle Tithonian (Windhauseniceras internispinosum Biozone). Second transgressive-regressive cycle develops between the middle Tithonian and the uppermost upper Tithonian (Windhauseniceras internispinosum to Substeueroceras koeneni Biozones). Third transgressive-regressive cycle includes upper Tithonian to upper Berriasian deposits (Substeueroceras koeneni to Spiticeras damesi Biozone), while fourth transgressive-regressive cycle includes upper Berriasian to lower