Las principales discordancias del Mesozoico de la Cuenca Neuquina según observaciones de superficie

Resumen

The main unconformities of the Mesozoic of the Neuquén Basin based on surface
observations. A general summary of the main unconformities which produced major order break-ups during
the evolution of the Mesozoic sedimentary infill of the Neuquén Basin is offered in this paper. Based on its
hierarchy, they are categorized in three groups, as follows: 1) key unconformities widely spread along the whole
basin; 2) «Intracuyan» unconformities related to the Dorsal de Huincul, and 3) «Intraprecuyan» unconformities
restricted to isolated depocentres. Having into account tectonic, eustatic, paleoclimatic and/or paleontological
aspects of the sedimentites situated below- and above of each unconformity, precisions about their ages are
given. The number of the recognized key unconformities sums 10, as follows: Huarpican (Intratriassic),
Rioatuelican (Intraliassic), Lotenican (Intracallovian), Araucanican (ca. Oxfordian/Kimmeridgian boundary),
Huncalican (Intravalanginian), Coihuequican (Intrahauterivian), Pampatrilican (Intrabarremian),
Pichineuquenican (Intraaptian), Patagonidican (ca. Albian/Cenomanian boundary) and Huantraiquican
(Intracampanian). In relationship with the area realated with the Dorsal de Huincul, three «intracuyan»
unconformities were identified, as follows: the Intratoarcian, only recognized at subsurface, the Seguelican
(Intrabajocian 1) and the Lohanmahuidican (Intrabajocian 2). However, the influence of these unconformities
diminish towards northern areas of the basin, as the distance increase with regard to the cited morphostructural
element. The «intraprecuyan» unconformities recorded in the Cordillera del Viento and Chachil depocentres
are of local character and less hierarchy. They are the result of short interruptions in the volcano-sedimentary
infill of these halfgrabens. Given its geographical restriction to the cited depocentres, no formal names were
ascribed to these unconformities. Once defined the key unconformities, a summary in three tables of genetically
related formational units bounded by them, using the classical lithostratigraphic categorization in Groups, the
latter ones basically coincident with the concept of tectosedimentary units (TSU), is presented. The obtained
results lead to suggest some new ideas with regard to the evolution of the Neuquén Basin and to keep attention
on still open nomenclatural problems.