Distinguishing Similar Volcanic Source Areas From An Integrated Provenance Analysis: Implications for Foreland Andean Basins

Abstract

The Mata Amarilla Formation marks the onset of the foreland stage of the Austral basin, which is composed of mostly nonmarine and littoral siliciclastic sediments, thus providing an opportunity to study the detrital record of the Late Cretaceous southern foreland Andes. Our dataset provides, for the first time, a comprehensive picture of the Late Cretaceous evolution of the Austral foreland basin, constituting a possible analogue to other foreland basins at the foot of the Andes. Sandstones from the Mata Amarilla Formation testify to variable contributions from Jurassic bimodal volcanic rocks of the Deseado Massif and the Patagonian fold-and-thrust belt, in the context of an eastward-advancing orogen. Sandstone petrography shows an overall feldspathic litharenite composition, whereas sandstones coming from the northeast (Deseado Massif) have higher Lv and lower Qp proportions than samples coming from the west (Patagonian fold-and-thrust belt). In the central part of the study area, sandstones are characterized by higher proportions of Qt associated with a greater distance and time of transport relating to its position in the Austral foreland basin. In spite of the increased maturity of sandstone in the central area, X-ray analyses permit recognition of the compositional signature of Mata Amarilla Formation, in which four claymineral assemblages were identified: S (rich in smectite), S-K (rich in smectite and kaolinite), Pg (rich in palygorskite), and I/S (rich in illite-smectite mixed layers). S-assemblage evidences well-crystallized smectite, characteristic of volcaniclastic origin. Most smectite was formed during early diagenesis through alteration of labile tuffaceous material derived from the Southern Andes. The stratigraphic variations in clay-mineral assemblages reveal a strong environmental control on their distribution. The transformation of smectite into illite and kaolinite is considered as product of pedogenesis, whereas the presence of palygorskite indicates a coastal environment with paleosol development under poorly drained conditions.

Refining stratigraphy and tectonic history using detrital zircon maximum depositional age: an example from the Cerro Fortaleza Formation, Austral Basin, southern Patagonia

“…(b) ‘Fluvial’ model after Varela et al . (,b, ). The towns of El Calafate and El Chalten are displayed to give spatial reference.…”

Cretaceous evolution of the Andean margin between 36°S and 40°S latitude through a multi‐proxy provenance analysis of Neuquén Basin strata (Argentina)

“…In the Central Andes of Argentina and Bolivia a clear regional foreland basin has been recognised since the Palaeogene; to the west in Chile evidence of contractional deformation and foreland basin deposition are described in the upper Cretaceous strata in the Atacama region (Mpodozis et al ., ; Arriagada et al ., ). In the Malargue region (northern Neuquen basin) foreland basin deposition started in the late Cretaceous and in the southern Andes of Patagonia the development of a foreland basin associated with the Patagonian fold and thrust belt has been described starting in the late Cretaceous (Wilson, ; Fildani & Hessler, ; Fosdick et al ., ; Varela et al ., ).…”

Fossil forests in the Austral Basin (Argentina) marking a Cenomanian heterogeneous forced regressive surface

“…It extends over the southernmost end of Argentina and Chile, and is surrounded to the east by the Deseado Massif (Macizo del Deseado) and to the west by the Patagonian-Fuegian Andes (Fig. The Mata Amarilla Formation displays the best outcrops of the lower Upper Cretaceous deposits in the Austral Basin, thus marking both the closure of the previous Marginal Rocas Verdes Basin and the beginning of the foreland stage of the Austral Basin (Varela et al, 2012b(Varela et al, , 2013. Three main tectonic stages of the Austral Basin have been identified (Biddle et al, 1986;Rodr ıguez & Miller, 2005;Richiano et al, 2012;Varela et al, 2012b): a rift stage, a stage of thermal subsidence, and, finally, a foreland stage.…”

“…The lower section of the Mata Amarilla Formation is characterized by mudstones with subordinate sandstones in the west attributed to distal fluvial environments, whereas towards the east it consists of a fining-upward succession of mudstones, heterolithic sediments with mixed-structures and sandstones with herringbone cross-bedding assigned to littoral environments (Fig. Finally, the upper section is also characterized by mudstones with subordinate fine-to medium-grained sandstones (Varela et al, 2013). The middle section is characterized by conglomerates to coarse-grained sandstones with subordinate mudstones in the west, whereas towards the east, it consists of medium-to coarse-grained sandstones with subordinate mudstones (Fig.…”

“…In the eastern part of the basin, six FAs were recognized: large-scale complex ribbon bodies, small-scale simple ribbon bodies, tabular mudstones and fine-grained sandstones, lobe-shaped bodies, fine-grained deposits and heterolithic deposits with continental fossils: plants, insects, freshwater fishes and dinosaurs Petrulevi cius et al, 2014). The LSM is the main fluvial system within the drainage network and has a north-east-south-west orientation, flowing towards the basin depocentre in the south-west (Varela et al, 2013;Varela, 2015). The braided fluvial system transitionally changes eastward to a HSM fluvial system with a sandy bedload.…”