This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This paper presents a detailed study of the tectonic subsidence evolution during the Late Triassic-Late Jurassic period in the central area of the Neuquén Basin. The methodology consisted of the integration of outcrop and subsurface data, in order to obtain tectonic subsidence curves for the analyzed period in the study area. The origin of the basin was linked to a lithospheric mechanical extension episode in the Late Triassic-Early Jurassic that, once completed, gave rise to a post-rift stage. The post-rift stage, comprised between Early Jurassic and Early Cretaceous, was classically assumed as dominated by thermal subsidence. Results obtained in this paper show that there is a change in the geometry of the tectonic subsidence curves, which depart considerably from the expected behavior for a basin dominated by thermal subsidence. Therefore, the post-rift stage of the Neuquén Basin for the study area would have had a more complex tectonic evolution than that determined exclusively by the thermal subsidence, and that superposition of mechanisms must be considered. From the available data, a shift from thermal to dynamic subsidence from the Middle Callovian onwards seems to be the most plausible explanation for the subsidence evolution observed in the study area.

We conducted a U–Pb–Hf isotope study on zircon crystals from ignimbrites of the Changhsingian to Olenekian (253–248 Ma) Los Menucos Basin in the North Patagonian Massif (NPM), Argentina, in order to evaluate the age and petrogenesis of the magmas. Additionally, a compilation of whole-rock geochemistry and U–Pb–Hf in zircon isotope data for the Permian to Middle Triassic rocks of the NPM, for comparison with our data, was made to assess whether Patagonia would have been an exotic terrane accreted to SW Gondwana during the late Palaeozoic. We interpret the available U–Pb–Hf data to suggest that northern Patagonia experienced eastward arc expansion from the early Permian, about 273 Ma ago. This ∼820 km arc expansion event involved crustal shortening and magmatism with high-silica adakitic affinity, resulting in Hf-isotopic pull-down. At 253 Ma, slab steepening became associated with the coeval emplacement of ignimbrites of the Los Menucos Basin, which involved post-orogenic to intraplate magmatism. During the Middle Triassic, a slab break-off triggered uplift and basaltic underplating, promoting the emplacement of dike swarms with C-type adakitic signature at 246–244 Ma. The Hf isotope data for SW Gondwana for the same period indicate distinct trends that are explained here by differential slab roll-back since the Guadalupian, in a slab-tearing setting. Therefore, Permian to Middle Triassic magmatism is interpreted as having been associated with an eastward-directed proto-Pacific subduction system, which ultimately supports an autochthonous origin for Patagonia.

No abstract