Márgenes costeros híbridos de la Cuenca Neuquina (Formación Allen, Cretácico Superior, Argentina).

Abstract

ABSTRACT. The Allen Formation records the first Ingression Atlantic to the Neuquén Basin during the Late Cretaceous. The definition of lithofacies and facies associations interpretation for stratigraphic sections in Paso Córdoba and Salitral Moreno area, Río Negro, Argentina allowed to establish the depositional system that characterized this transgression in the northeastern edge of the Basin. In this paper we present sedimentological analysis of conglomeratic, sandstone, heterolithic and pelitic facies, which allowed the interpretation of tidal channels (TC), intertidal flats (ITF), stormsinfluenced tidal flat (SITF), subtidal flat (STF) and shoreface deposits (SF) parts of the depositional environment. These deposits represent a sedimentary records preserved example of hybrid systems, in which, the base of the sequence has greater tidal influence, while the upper portion is dominated by wave action. The paleocurrent data indicating a NNW-SSE direction to the shore and correlations and spatial distribution of facies associations propose paleogeographic and paleoenvironmental interpretations to Malargüe Group base. Then in this paper the relationship of this coastal environment presents with wind systems previously defined in this area for the Allen Formation.

Vertebrate tracks from the Paso Córdoba fossiliferous site (Anacleto and Allen formations, Upper Cretaceous), Northern Patagonia, Argentina: Preservational, environmental and palaeobiological implications

“…unconformity (e.g., Hugo and Leanza, 2001;Leanza et al, 2004;Leanza, 2009;Garrido, 2010). However, there is no uniformity of criteria regarding this limit in the Paso C ordoba area, so both a transitional (see Paz et al, 2014;Armas and S anchez, 2015) and an erosive discordance (Hugo and Leanza, 2001) have been suggested.…”

“…The Huantraiquican unconformity is well exposed in the area of Cinco Saltos and Lago Pellegrini, both in the Río Negro province (Leanza, 2009), but in Paso C ordoba its existence is discussed. Hugo and Leanza (2001) suggested that, in fact, there is an erosive discordance between the red/purple mudstone of the Anacleto Formation and the yellowish sandstones of Allen Formation, but Paz et al (2014) and Armas and S anchez (2015) have recently studied some stratigraphical sections in that area and proposed a transitional passage between both formations, which would owe to the gradual evolution of the depository system. According to the stratigraphical, facial and palaeoenvironmental analyses presented in this contribution, we observed no clear changes or unconformities in the Cañad on del Desvío, which would allow a reinforce the proposal of transitional passage between both formations.…”