Cenozoic provenance history of synorogenic conglomerates in western Argentina (Famatina belt): Implications for Central Andean foreland development

Abstract

In Famatina, at the modern northern fl atslab segment of the Central Andean belt, synorogenic conglomerate facies provide a unique opportunity to reconstruct paleogeography and tectonic setting. Stratigraphically constrained provenance analyses record a multievent history of the Andean foreland and a complex pattern of exhumed uplands, which, in turn, controlled the depocenter history. Western and eastern sources can be differentiated. The western domain was composed of equigranular granitoids and lower and upper Paleozoic volcano-sedimentary and sedimentary units, whereas the eastern domain was mainly formed by porphyrytic granitoids and minor slightly metamorphosed lower Paleozoic clastic rocks. The surrounding regions expose medium-to high-grade metamorphic rocks, which are not recorded in any Cenozoic conglomerate of Famatina. Unroofi ng sequences can be deduced from the compositional trends. Conglomerate composition and paleocurrent data show input from intrabasinal sources and important participation of basement since the beginning of the Neogene. We infer an early Miocene broken foreland during deposition of the Del Crestón Formation. A signifi cant source inversion, with clasts supplied from the eastern basement domain, is recorded ~2000 m from the base, within the middle Miocene Del Abra Formation; reactivation of western granitic thrust sheets occurred by the late middle Miocene and late Miocene, as indicated by provenance studies of the Santo Domingo and El Durazno Formations. In contrast to simple asymmetric foreland models, provenance analysis documents early participation of crystalline rocks, suggesting early development of intraforeland basement highs within the southern Central Andes. At a regional scale, basement thrusting and associated intermontane basin development were diachronous. This interpretation is supported by broad propagation of basement thrusting from the northern Sierras Pampeanas (and Famatina) toward the central and eastern Sierras Pampeanas between early-middle Miocene and late Miocene-Pliocene time. Early Miocene reconstructions of the Juan Fernandez Ridge position on the Central Andean margin suggest that during this interval, shallow subduction was likely unrelated to oceanic plateau subduction under the Sierras Pampeanas.

Magnetostratigraphy and paleomagnetism of early and middle Miocene synorogenic strata: basement partitioning and minor block rotation in Argentine broken foreland

“…The Cenozoic stratigraphy of Famatina is composed of over 3,500-m-thick alluvial strata represented by the Del Crestón Formation, overlain by the Mio-Pliocene Angulos Group and the Pleistocene Santa Florentina Formation Dávila and Astini 2007). In this work, we focus on the two megasequences recorded in the Del Crestón Formation, MS1 and MS2.…”

“…In this region, within the Famatina belt, a thick Early Miocene synorogenic megasequence, known as the Del Crestón Formation Astini 2002, 2003a, b;Dávila et al 2004), underlays the widespread Mio-Pliocene successions of the NW Sierras Pampeanas. This unit has been recently dated and interpreted to record the initiation of sedimentation within the Andean broken foreland (Dávila et al 2004;Dávila and Astini 2007). This succession also records the magmatic broadening in the southern Central Andes, probably associated with the initiation of shallow subduction and changes in the convergence rates of the South American and Nazca plates (Dávila and Astini 2007;Dávila 2010).…”

“…This unit has been recently dated and interpreted to record the initiation of sedimentation within the Andean broken foreland (Dávila et al 2004;Dávila and Astini 2007). This succession also records the magmatic broadening in the southern Central Andes, probably associated with the initiation of shallow subduction and changes in the convergence rates of the South American and Nazca plates (Dávila and Astini 2007;Dávila 2010).…”

“…The southern segment of the Central Andes is characterized by a complex volcanic and tecto-sedimentary evolution, both in time and space (e.g., Jordan et al 1983Jordan et al , 1993Jordan et al , 2001Marrett and Strecker 2000;Kay and Mpodozis 2002;Dávila and Astini 2007). This evolution has been recorded in numerous retroarc foreland basins and subbasins, which contain thousands of meters of clastic continental deposits, frequently intercalated with pyroclastic products from the western volcanic arc (Ramos 1999).…”

Low-grade metamorphism of Cambro-Ordovician successions in the Famatina belt, Southern-Central Andes: Burial-inversion history linked to the evolution of the proto-Andean Gondwana margin

“…Dávila and Astini, 2007). VAS: Valle La Aguadita thrust sheet; SPS: Sierra de Paimán thrust sheet; RS:…”