Thermochronological constraints on the Cambrian to recent geological evolution of the Argentine passive continental margin

SEBASTIAN KOLLENZ, ULRICH A. GLASMACHER, EDUARDO A. ROSSELLO, DANIEL F. STOCKLI, RICARDO E. PEREYRA

TECTONOPHYSICS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 p. 182 - 203

0040-1951

Passive continental margins are geo-archives that store information from the interplay of endogenous and exogenousforces related to continental rifting, post-breakup history, and climate changes. The recent South Atlantic passive continentalmargins (SAPCMs) in Brazil, Namibia, and South Africa are partly high-elevated margins (~ 2000 m a.s.l.), andthe recent N-S-trending SAPCM in Argentine and Uruguay is of low elevation. In Argentine, an exception in elevation isarising from the higher topography (> 1000 m a.s.l.) of the two NW-SE-trending mountain ranges Sierras Septentrionalesand Sierras Australes. Precambrian metamorphic and intrusive rocks, and siliciclastic rocks of Ordovician to Permian agerepresent the geological evolution of both areas. The Sierras Australes have been deformed and metamorphosed (incipient- greenschist) during the Gondwanides Orogeny. The low-temperature thermochronological (LTT) data (< 240 °C) indicatedthat the Upper Jurassic to Lower Cretaceous opening of the South Atlantic has not completely thermally reset thesurface rocks. The LTT archives apatite and zircon still revealed information on the pre- to post-orogenetic history of theGondwanides and the Mesozoic and Cenozoic South Atlantic geological evolution. Upper Carboniferous zircon (U-Th/He)-ages (ZHe) indicate the earliest cooling below 180 °C/1 Ma. Most of the ZHe-ages are of Upper Triassic to Jurassicage. The apatite fission-track ages (AFT) of Sierras Septentrionales and the eastern part of Sierras Australes indicate theSouth Atlantic rifting and, thereafter. AFT-ages of Middle to Upper Triassic on the western side of the Sierras Australesare in contrast, indicating a Triassic exhumation caused by the eastward thrusting along the Sauce Grande wrench. Thecorresponding t-T models report a complex subsidence and exhumation history with variable rates since the Ordovician.Based on the LTT-data and the numerical modelling we assume that the NW-SE-trending mountain ranges received theirgeographic NW-SE orientation during the syn- to post-orogenetic history of the Gondwanides.