Late Cretaceous Uplift in the Malargüe fold-and-thrust belt (35ºS), southern Central Andes of Argentina and Chile

Abstract

ABSTRACT. The Cordillera de los Andes is the typical example of a subduction-related orogen. Its present topography is the result of post-Miocene uplift, however, Andean compressional deformation and uplift started in the Late Cretaceous, as increasingly recognized in different sectors of the mountain belt. We present evidences of a Late Cretaceous event of compressional deformation in the southern Central Andes (35ºS), reflected in syn-orogenic foreland basin deposits assigned to the Neuquén Group in Argentina and the Brownish-Red Clastic Unit in Chile. Comparison of the facies of these units allows us to recognize a sector proximal to the Late Cretaceous orogenic front, a distal sector with sediment provenance from the forebulge and a western sector where the sediments where deposited within the Late Cretaceous mountain belt. On this basis, we assign the orogenic front to an inverted Jurassic normal fault, the Río del Cobre fault, and reconstruct the structure of the easternmost Late Cretaceous Andes at this latitude. The change in the location of the orogenic front north and south of 35ºS allows us to recognize a long-lived change in behavior in Andean evolution in this sector, which correlates with a change in the shape and the deposits of Mesozoic Neuquén basin. RESUMEN. Levantamiento Cretácico Tardío en la faja plegada y corrida de Malargüe (35ºS), Andes Centrales del sur, Argentina y Chile. La Cordillera de los Andes es el ejemplo típico de un orógeno asociado a subducción. Si bien su topografía actual es el resultado del levantamiento posterior al Mioceno, la deformación y el levantamiento ándicos comenzaron a partir del Cretácico Tardío, como se reconoce actualmente en diversos sectores de la faja montañosa. En este trabajo se presentan evidencias de un evento de deformación compresiva durante el Cretácico Tardío en los Andes Centrales del sur (35ºS) reconocido a partir de los depósitos sinorogénicos asociados, que se asignan al Grupo Neuquén en Argentina y la ʻUnidad Clástica Café-Rojiza' (BRCU) en Chile. Mediante las variaciones de facies en estos depósitos se pueden reconocer un sector proximal cercano al frente orogénico Cretácico Tardío, un sector distal con aporte desde el dorso periférico, y un sector occidental en el que los depósitos se produjeron dentro del cordón montañoso. De esta manera, se puede ubicar el frente orogénico Cretácico Tardío, el que asignamos a la inversión tectónica de una falla normal jurásica, la falla Río del Cobre. El cambio en la ubicación del frente orogénico Cretácico al norte y sur de 35ºS permite reconocer a este sector como un límite entre sectores con diferencias en su evolución andina, que se interpreta como heredado de la evolución de la cuenca Neuquina.

Tectonic Regimes of the Central and Southern Andes: Responses to Variations in Plate Coupling During Subduction

“…A Late Cretaceous onset of Andean orogenesis is recorded by a shift to nonmarine synorogenic sedimentation in Argentina and Chile (Neuquén Group, Las Chilcas Formation, and equivalent units). Although provenance data show continued derivation from both the arc and craton (Balgord & Carrapa, ; Mescua et al, ; Tunik et al, ), a sharp increase in sediment accommodation accompanied by thrust‐related growth strata and focused exhumation demonstrate the contractional nature of the episode (Fennell et al, ; Folguera, Bottesi, et al, ; Horton & Fuentes, ; Horton et al, ). This initial foreland basin is defined by proximal clastic deposits in the Central Valley (Las Chilcas Formation; Boyce, ; Charrier et al, ) and the Principal Cordillera (Brownish‐Red Clastic Unit; Charrier et al, , ).…”

The fracture network, a proxy for mesoscale deformation: Constraints on layer parallel shortening history from the Malargüe fold and thrust belt, Argentina

“…Even though the onset of the compressive deformation is not well constrained, in the study area between 35°S and 36°S, sedimentological evidence supports the initiation of a foreland stage at the end of the Cretaceous times, possibly produced by the early uplift of an adjacent early back‐arc belt [ Mescua et al ., ; Ramos and Folguera , ; Ramos et al ., ; Tunik et al ., ]. Indeed, Late Cretaceous uplift in the western Malargüe fold and thrust belt (MFTB) has been recently identified, reflected in the sedimentation of synorogenic foreland basin deposits assigned to the Neuquén Group and its equivalent in Chile, known as the Brownish‐Red Clastic Unit [ Mescua et al ., ]. Clast composition suggests that the exhumation of Late Jurassic strata occurred in Late Cretaceous times and probably also in Paleogene times.…”

Cretaceous Intraplate Contraction in Southern Patagonia: A Far‐Field Response to Changing Subduction Dynamics?

“…Understanding the tectonic evolution of the Deseado FTB has paleogeographical, evolutionary, and even oil exploration implications. For instance, decoding early orogenic activity in Patagonia would contribute to the general discussion between studies favoring an early development of the whole Andes in Cretaceous times (e.g., Fildani et al, ; Folguera & Iannizzotto, ; Jaimes & De Freitas, ; Martin‐Gombojav & Winkler, ; Mescua et al, ; Mpodozis et al, ; Sempere, ; Soler & Bonhomme, ; Tunik et al, , among others) and works that only contemplate Cenozoic Andean mountain building stages (e.g., Armijo et al, ; Faccenna et al, ; Husson et al, ; Oncken et al, , among others). In addition, it is crucial to understand sediment source areas to neighboring Austral and San Jorge Gulf oil‐bearing basins (e.g., Barberón et al, ; Limarino & Giordano, ; Malkowski et al, ; Figure a) and to shed light into Mesozoic paleobiogeography in Patagonia which has the richest fossil record of South America (Wilf et al, ).…”