Peritidal cyclic sedimentation from La Manga Formation (Oxfordian), Neuquén Basin, Mendoza, Argentina

Abstract

The La Manga Formation consists of marine carbonates and represents most of the sedimentary record of the Callovian-Oxfordian in the Neuquén Basin. Three localities in the southern Mendoza province were studied and their cyclicity was determined by means of facies analysis and their vertical arrangement. Facies of inner ramp, that were deposited in extremely shallow-water environments with intermittent subaerial exposures have been broken down into shallow subtidal, and intertidalesupratidal environ-ments. Shallow subtidal facies are arranged into decimetre scale upward-shallowing cycles composed of marls, laminated or massive mudstones or bioclastic wackestones and intraclastic wackestone-pack-stones. Intertidal-supratidal centimetre-scale cycles consist of an upward-shallowing succession of restricted facies, overlaid by horizontal or crinkle microbial laminites, flat pebble conglomerates or breccias beds. The defined cycles show a shallowing upward trend in which the evidence of relative sea-level lowering is accepted. The interpretation of Fischer plots allowed the recognition of changes in accommodation space. (R.M. Palma), diegokietzmann@gl.fcen.uba.ar (D.A. Kietzmann), gbressan@gl.fcen.uba.ar (G.S. Bressan), j.m.chivelet@geo.ucm.es (J. Martín-Chivelet), jlopez@geo.ucm.es (J. López-Gómez), mefarias@proimi.org.ar (M.E. Farias), mpiglesia@gl.fcen.uba.ar (M.P. Iglesias Llanos).

Palaeoenvironmental significance of middle Oxfordian deep marine deposits from La Manga Formation, Neuquén Basin, Argentina

“…(middle Oxfordian). Also, these shallower facies are similar to those observed in the upper part of La Manga Formation in the localities of Yeseras Grandes and Arroyo La Manga, and are interpreted as intertidal-supratidal deposits (Palma et al, 2012(Palma et al, , 2013.…”

“…However, in zones close to Arroyo La Manga and Codo del Blanco (Palma et al, 2012(Palma et al, , 2013 time-equivalent deposits correspond to outer ramp facies.…”

“…It should be mentioned that deposits laterally equivalent to those of Arroyo Los Blancos, but consisting of much shallower facies, occur in the proximities of the section under study (Palma et al, 2013) and contain specimens of Mirosphinctes sp. (middle Oxfordian).…”

“…Interestingly, in all outcrops, the deposits of the top of La Manga Formation are characterized by low-energy, subtidal and peritidal facies (Palma et al, 2013), showing a sharp, non-transitional, contact between deep marine/outer ramp deposits and peritidal deposits.This probably reflects an interval of rapidly decreasing accommodation causing a regional forced regression (Palma et al, 2010(Palma et al, , 2013.…”

“…These deposits include outer carbonate ramp, middle ramp, inner ramp margin (patch reef), and inner ramp facies (Legarreta, 1991;Palma et al, 2007Palma et al, , 2009Palma et al, , 2011Palma et al, , 2013. Due to economic interests, these carbonate ramp sediments have been extensively investigated and many sequence stratigraphic and palaeogeographical data are available (Mitchum and Uliana, 1985;Legarreta and Uliana, 1996; among others).…”