Faulting and erosion in the Argentine Precordillera during changes in subduction regime: Reconciling bedrock cooling and detrital records

Abstract

The Argentine Precordillera is an archetypal retroarc fold-and-thrust belt that records tectonics associated with changing subduction regimes. The interactions between exhumation and faulting in the Precordillera were investigated using apatite and zircon (U-Th-Sm)/He and apatite fission track thermochronometry from the Precordillera and adjacent geologic domains. Inverse modeling of thermal histories constrain eastward insequence rock cooling associated with deformation and erosion from 18 to 2 Ma across the Central Precordillera tracking thrusting during this time. The youngest AHe ages (5-2 Ma) and highest erosion rates are located in the eastern and western extremities of the Precordillera and indicate that recent denudation is concentrated at its structural boundaries. Moreover, synchronous rapid Pliocene cooling of the Frontal Cordillera, Eastern Precordillera, and Sierra del Valle Fértil was coeval with initiation of basementinvolved faulting in the foreland. Detrital zircon U-Pb geochronology from the ca. 16-8.1 Ma Bermejo foreland basin strata suggests fluvial connectivity westward beyond the Frontal Cordillera to the Main Cordillera and Coast Range followed by an important shift in sediment provenance at ca. 10 Ma. At this time, we suggest that a substantial decrease in

Thermochronologic Evidence for Late Eocene Andean Mountain Building at 30°S

“…(left) Shaded relief map of the Andes between 22° and 35°S showing the regional extension of the Eocene relief. After Hong et al () and Oncken et al () between 23° and 27°S, Rossel et al () between 28° and 29°S (Valeriano Fault zone), and Fosdick et al () (Colangüil Range), and this work at 30°S (Guanta and Colangüil ranges). PrC: Precordillera; PR: Pampean Range; SBS: Santa Bárbara System.…”

“…By the early to middle Miocene, the magmatic arc was established over the El Indio Belt (Figure b) and was accompanied by tectonic inversion of the Oligocene extensional faults and the development of new structures concentrated within this region (Giambiagi et al, ; Martin, Clavero, & Mpodozis, ; Rodríguez, ; Winocur et al, ). Finally, during middle to late Miocene magmatic activity diminished as the Nazca plate shallowed, and the deformation front migrated eastward, sequentially exhuming the Colangüil range (Fosdick et al, ) and the Precordillera (Suriano et al, ) on the eastern slope of the Andes. Since ~5 Ma active shortening has been located in the easternmost Precordillera and Pampean broken foreland, as a consequence of the established flat slab setting (Ramos et al, ; Siame, Bellier, & Sebrier, ).…”

Mio-Pliocene aridity in the south-central Andes associated with Southern Hemisphere cold periods

“…C exhumation is the amount of 10 Be in the sample acquired during recent exhumation. At Huaco it is estimated using long-term exhumation rates derived from apatite U-Th/He dating (29). At Toro Negro it is estimated from exhumation rates computed from the concentration of muogenic 36 Cl in K-rich feldspars.…”

“…Likewise, most terrestrial sediments are deposited in association with active mountain belts, creating the additional challenge of deconvolving regional climatic signals from local tectonic-orographic signals. These issues are especially challenging in the south-central Andes where a regionally extensive climate transition in the latest Miocene (14, 27, 28) appears synchronous with significant tectonic uplift at this time (29)(30)(31)(32). It thus remains unclear whether the timing and extent of latest Miocene landscape ecologic changes in the south-central Andes were primarily controlled by tectonic-orographic effects or by globalscale changes in climate (e.g., refs.…”

Cenozoic Shift From Compression to Strike‐Slip Stress Regime in the High Andes at 30°S, During the Shallowing of the Slab: Implications for the El Indio/Tambo Mineral District

“…On the other hand, Bissig et al () argue that gold deposition occurred several million years after this shortening phase. Indeed, by the time of ore deposition in the metallogenic belt, crustal shortening was focused eastward, in the Argentine Precordillera fold‐and‐thrust belt (Allmendinger & Judge, ; Fosdick et al, ; Japas et al, ; Levina et al, ; Mardonez et al, ; Suriano et al, ), and few studies describe structures other than those accommodating Miocene‐Holocene contraction along the arc and backarc regions. In yet another interpretation, Charchaflié et al () describe normal faults in the northern sector of the belt, in the Veladero area (29.3°S), generated during the 15 to 10 Ma period, apparently controlling the emplacement of ore deposits.…”