Late Pleistocene to Recent Deformation in the Thick‐Skinned Fold‐and‐Thrust Belt of Northwestern Argentina (Central Calchaquí Valley, 26°S)

Abstract

The thickskinned fold-and-thrust belt on the eastern flank of the Andean Plateau in northwestern Argentina (NWA) is a zone of active contractional deformation characterized by fault-bounded mountain ranges with no systematic spatiotemporal pattern of tectonic activity. In contrast, the thinskinned Subandean fold-and-thrust belt of northern Argentina and southern Bolivia is characterized primarily by in-sequence (i.e., west to east) fault progression, with a narrow zone of Quaternary deformation focused at the front of the orogenic wedge. To better understand how recent deformation is accommodated across these mountain ranges and the Argentinian portion of the orogen in particular, estimating and comparing deformation rates and patterns across different timescales is essential. We present Late Pleistocene shortening rates for the central Calchaquí intermontane valley in NWA associated with at least three episodes of deformation. Global Positioning System data for the same region reveal a gradual decrease in horizontal surface velocities from the Eastern Cordillera toward the foreland, which contrasts with the rapid velocity gradient associated with a locked décollement in the Subandean Ranges of southern Bolivia. Our new results represent a small view of regional deformation that, when considered in combination with the shallow crustal seismicity and decadal-scale surface velocities, support the notion that strain release in NWA is associated with numerous slowly deforming structures that are distributed throughout the orogen. The thickskinned fold-and-thrust belt of NWA comprises the basement-cored uplifts of the Eastern Cordillera (EC) and the Santa Bárbara System (SBS) (Figure 1) that form unconnected topographic

Identification of Debris‐Flow Channels Using High‐Resolution Topographic Data: A Case Study in the Quebrada del Toro, NW Argentina

“…Our study area is the Eastern Cordillera of the northwestern Argentine Andes where debris flows and landslides are a common phenomenon (e.g., Cencetti & Rivelli, 2011; Hermanns et al., 2001; Olen & Bookhagen, 2018, 2020; Purinton & Bookhagen, 2020; Tofelde et al., 2017; Wayne, 2011). Active tectonic deformation (Figueroa et al., 2021; Marrett & Strecker, 2000) and hydro‐meterological extreme events (Castino et al., 2017) promote slope instabilities and frequently trigger debris flows that can threaten local populations and infrastructure. The high debris‐flow density together with steep gradients of topography, rainfall, and erosion make the Eastern Cordillera representative of many high‐relief regions worldwide and an ideal natural laboratory in which to study the topographic signature of debris flows.…”

Tectonic Control on Drainage Evolution in Broken Forelands: Examples From NW Argentina

“…Many of these longitudinal rivers contain multiple prominent knickpoints (Figures 5a and S4 in Supporting Information S1). The majority of knickpoints are located at lithologic contacts or adjacent to thrust faults (Figures 5a and S4 in Supporting Information S1; Figueora et al., 2020; Olen & Bookhagen, 2020 and references therein; Savi et al., 2016; Trauth et al., 2000). However, we find several knickpoints of “unknown” origin which may be related to stream capture events (Figures 5a and S4 in Supporting Information S1; e.g., Bishop, 1995).…”

“…The modern contractional basin and range style broken foreland is characterized by ongoing shortening accommodated by ∼N‐S‐striking, high‐angle reverse faults that cut through the crust to depths of >25 km (Figure 2a; e.g., Figueora et al., 2020). Uplift along these faults caused fragmentation and compartmentalization of the foreland, with the formation of steep, basement‐cored ranges, separated by wide intermontane flexural basins with limited accommodation space (e.g., Cristallini et al., 2004; Strecker et al., 2012).…”

Seismotectonics of the thick-skinned Santa Bárbara System in northwestern Argentina: implications for regional crustal rheology and structure

“…Major differences between the thin-and thick-skinned sectors of the Andean foreland also exist with respect to geodetically determined, decadal-scale deformation patterns. For example, instead of the steep gradient in horizontal surface velocity documented across the SA [e.g., Brooks et al, 2011;Weiss et al, 2016], GPS data from the thick-skinned sectors including the SBS and adjacent Eastern Cordillera and Andean Plateau morphotectonic provinces display a gradual decrease in horizontal surface velocities from west to east [Figueroa et al, 2021]. This decrease suggests a kinematic style that might be related to either a deep-seated, rheologycontrolled décollement, multiple detachment levels, the complete lack of basal low-angle faulting, faulting across isolated and widely distributed steep, basement-cored faults, or a combination of these factors.…”