U-Pb and Lu-Hf zircon geochronology of the Cañadón Asfalto Basin, Chubut, Argentina: Implications for the magmatic evolution in central Patagonia

Abstract

The Cañadón Asfalto basin, central Chubut, Argentina, comprises a volcano-sedimentary sequence related to the opening of the Atlantic Ocean during Mesozoic times. The Lonco Trapial, Cañadón Asfalto and Cañadón Calcáreo formations are the main units related to the evolution of this basin. The Las Chacritas and Puesto Almada members are distinguished in the Cañadón Asfalto Formation. LA-HR-ICP-MS U-Pb and Lu-Hf data on zircon were obtained on these units. The Lonco Trapial Formation gave a weighted average age of 172.3±1.8 Ma. A pyroclastic level from the Las Chacritas Member gave a weighted average age of 168.2±2.2 Ma. Two U-Pb concordant ages of 160.3±1.7 Ma on a laminated tuffite and 158.3±1.3 Ma on a pyroclastic level were obtained for the Puesto Almada Member. Two maximum depositional ages constrain the sedimentary provenance areas for the basin: 1) A sample from the Sierra de la Manea range, where a

Cretaceous-Cenozoic growth of the Patagonian broken foreland basin, Argentina: Chronostratigraphic framework and provenance variations during transitions in Andean subduction dynamics

“…Prior to the main phase of Andean shortening, prolonged Late Triassic-Early Cretaceous extension was associated with Gondwana breakup and opening of the South Atlantic (Franzese et al., 2003;Ramos, 2009). Mesozoic normal faults bounding extensional basins (e.g., the Early Jurassic Cañadón Asfalto Basin; Hauser et al, 2017) were later reactivated during Andean shortening in hinterland and foreland regions (Bilmes et al, 2013;Echaurren et al, 2016).…”

“…8B From the detrital zircon samples, 4 samples (17PDS04, 17TQT01, 17CUS02, 17ESQ01) were selected for Hf isotope analyses in order to assess Mesozoic-Cenozoic crustal evolution and magmatic patterns from to 10 Ma (e.g., Pepper et al, 2015;Balgord, 2017). A total of new analyses are combined with 43 published Hf isotopic results from samples of sandstones (Hauser et al, 2017) and modern river sand results (Pepper et al, 2015) into a single Hf evolution diagram (Fig. 7).…”

Phylogenetic analysis of Gondwanan basal eusauropods from the Early-Middle Jurassic of Patagonia, Argentina

“…This position does confi rm the original assessment of Bonaparte (1986a), in that Patagosaurus and Cetiosaurus share a close phylogenetic affi nity. Both are from roughly the same age; Patagosaurus from the early Middle Jurassic (likely Aalenian-Bajocian), Cetiosaurus oxoniensis from the Bathonian, and the Rutland Cetiosaurus being Bajocian in age (Cox et al, 1992;Upchurch & Martin, 2002Liston, 2004aListon, , 2004bBarrett, 2006;Noè, et al, 2010;Cúneo et al, 2013;Hauser et al, 2017). Further research, especially on the Rutland Cetiosaurus, might give more information on the precise relationships between these taxa and whether or not the 'cetiosaurs' as a group are in need of revision.…”

Lower Jurassic felsic diatreme volcanism recognized in central Patagonia as evidence of along-strike rift segmentation

“…A second extensional phase is recorded in the South CPB domain, and it is represented by pull-apart sedimentation (Cañadón Asfalto Formation) during the Toarcian and Bajocian ages (Bouhier et al 2017;Hauser et al 2017). Continental fluvial and deep lacustrine sedimentary rocks were deposited interdigitated with andesitic and dacitic lavas (Figari and Courtade, 1993;Cortinas, 1996;Cuneo et al 2013;Figari et al 2016;Hauser et al 2017;Bouhier et al 2017). The dacitic ignimbrites facies are subordinated to the effusive ones (Figari et al 2016;Bouhier et al 2017).…”