The Vaca Muerta transgression (Upper Jurassic), Neuquén Basin, Argentina: Insights into the evolution and timing of aeolian–marine transitions

Abstract

Considering the evolution of aeolian to marine transitions for the geological record, either catastrophic or gradual transgressive scenarios showing high or low rates of coastal migration have been proposed. A critical evaluation of modern analogues suggests that a catastrophic transgression shares many characteristics with Holocene transgressions, yet they are caused by different rates of sea-level rise. The present study provides insights into the evolution of aeolian to marine transitions in order to discuss these alternative scenarios of sea-level rise. For this purpose, a sedimentological and ichnological analysis was carried out on ten stratigraphic sections of the Pic un Leuf u area, Argentina. There, marine deposits of the Vaca Muerta Formation accumulated over the aeolian deposits of the Quebrada del Sapo Formation during the early Tithonian. The sedimentary evolution of the transition can be summarized in: (i) a shutdown of aeolian dune field deposition, generating a planation surface in somewhat elevated areas and reworked megadunes in lowlands; (ii) beach sedimentation caused by episodic marine flooding that contributed to megadune reworking; and (iii) deposition in an embayed marginal-marine setting at the coast, recorded by bay margin bindstone, proximal bay and distal bay sedimentation. This transition indicates very rapid coastline migration and a condensed Transgressive Systems Tract succession throughout the study area. Rates of sea-level rise similar to Holocene ones (millimetres to centimetres per year) may have produced the transition between the Quebrada del Sapo and Vaca Muerta formations. The Late Jurassic represents a non-glacial time, and the global sea-level maximum highstand pre-dated the Vaca Muerta 2732

Authigenic‐cemented pebbles formed during Pleisto–Holocene transgression of gently inclined coastal plains

“…Particularly, low‐relief coastal areas are still in geomorphological disequilibrium because even small vertical changes in sea‐level resulted in extremely rapid migration of the coastline (e.g. Wetzel et al ., 2017; Paz et al ., 2021). Consequently, MDAC‐cemented pebbles may mark rapid transgressions (= rapid landward migration of coastline) across a low‐gradient coastal plain, which was subsequently covered by a thin sediment layer only and, thus, have not only environmental but also morphological significance.…”

Microbial mats and their palaeoenvironmental analysis in offshore – shelf facies of the Los Molles Formation (Toarcian – Lower Callovian) in the Chacay Melehue area, Neuquén Basin, Argentina

“…Fossil records of microbial activity in shallow coastal environments is well known (Carmona et al., 2012; Homann et al., 2015; Noffke, 2010; Noffke et al., 2008, 2013; Paz et al., 2021, 2022; Schieber et al., 2007; Seckbach & Oren, 2010; Tang et al., 2012). However, they are less common in deeper settings such as offshore or shelf environments (Banerjee & Jeevankumar, 2005; Logan et al., 1999; Noffke et al., 2002, 2003; Noffke, Beukes, et al., 2006; Noffke, Eriksson, et al., 2006; Pflüger, 1999).…”

“…Fossil records of microbial activity in shallow coastal environments is well known (Carmona et al, 2012;Homann et al, 2015;Noffke, 2010;Noffke et al, , 2013Paz et al, 2021Paz et al, , 2022Schieber et al, 2007;Seckbach & Oren, 2010;Tang et al, 2012).…”

“…Although there are mentions of fossil microbial mats in some formations in the Neuquén Basin (Comerio et al, 2014;Kietzmann et al, 2011;Paz et al, 2021;Tunik et al, 2009), those studies are mostly focused on a regional scale. For this reason, the importance of this contribution is that it represents the first study focused particularly on the description and characterization of the fossil microbial mats in the Los Molles Formation, in offshore to shelf environments, affected by storms, and density currents (Campetella et al, 2020;Ponce et al, 2015).…”

Organic-rich, fine-grained contourites in an epicontinental basin: The Upper Jurassic-Lower Cretaceous Vaca Muerta Formation, Argentina

“…In terms of sedimentary environments, the succession in the study area encompass beach, open bay, basin, slope and contourite drift environments (Paz, 2021). The beach and open bay deposits occur at the base of the Vaca Muerta Formation, and comprise massive, parallel-, low-angle and current-ripple cross-laminated, medium-to coarse-grained sandstone with local mudstone drapes, overlain by bindstone, and massive (bioturbated) to wavy, calcareous to mixed mudstone (Paz, 2021;Paz et al, 2021).…”