The evolution of the high‐elevated depocenters of the northern Sierras Pampeanas (ca. 28˚ SL), Argentine broken foreland, South‐Central Andes: the Pipanaco Basin

Abstract

The Pipanaco Basin, in the southern margin of the Andean Puna plateau at ca. 28°SL, is one of the largest and highest intermontane basins within the northernmost Argentine broken foreland. With a surface elevation >1000 m above sea level, this basin represents a strategic location to understand the subsidence and subsequent uplift history of high‐elevation depositional surfaces within the distal Andean foreland. However, the stratigraphic record of the Pipanaco Basin is almost entirely within the subsurface, and no geophysical surveys have been conducted in the region. A high‐resolution gravity study has been designed to understand the subsurface basin geometry. This study, together with stratigraphic correlations and flexural and backstripping analysis, suggests that the region was dominated by a regional subsidence episode of ca. 2 km during the Miocene‐Pliocene, followed by basement thrusting and ca. 1–1.5 km of sediment filling within restricted intermontane basin between the Pliocene‐Pleistocene. Based on the present‐day position of the basement top as well as the Neogene‐Present sediment thicknesses across the Sierras Pampeanas, which show slight variations along strike, sediment aggradation is not the most suitable process to account for the increase in the topographic level of the high‐elevation, close‐drainage basins of Argentina. The close correlation between the depth to basement and the mean surface elevations recorded in different swaths indicates that deep‐seated geodynamic process affected the northern Sierras Pampeanas. Seismic tomography, as well as a preliminary comparison between the isostatic and seismic Moho, suggests a buoyant lithosphere beneath the northern Sierras Pampeanas, which might have driven the long‐wavelength rise of this part of the broken foreland after the major phase of deposition in these Andean basins.

Dynamic uplift during slab flattening

“…This episode temporally matches the formation of the foreland landscapes in Peru and Argentina (Espurt et al, 2007;Dávila et al, 2012) ). The subduction angles vary along strike from flat (0˚) to a typical (30˚) for South America and the density contrasts (∆) of the slab (with respect to the mantle) are controlled by the slab age, the inferred crustal thickness and the Benioff zone geometry ( Fig.…”

“…1b): the Sierras Pampeanas broken foreland (often used as a modern analogue for the US Laramide, Jordan and Allmendinger, 1986). The Sierras Pampeanas are isostatically uncompensated and have associated high-elevation depocenters >1 km above sea level (Dávila et al, 2012). These features date to the latest Miocene-Pliocene, coeval with the advent of flat subduction (Ramos, 2009).…”

Using a Paleosurface to Constrain Low‐Temperature Thermochronological Data: Tectonic Evolution of the Cuevas Range, Central Andes

“…Bense et al () have suggested that most of the relief formation and rock exhumation took place during the Permo‐Triassic based on thermal modeling of these old thermochronologic ages. In contrast, several studies have proposed Miocene relief development based on the Miocene stratigraphic record and thermal modeling (Bense et al, ; Davila et al, ; Mortimer et al, ; Sobel & Strecker, ; Zapata et al, ).…”

An Ecological Overview of Halophytes from Arid Inland Environments of Argentina

“…1000 m a.s.l. ), located in the northern part of the Sierras Pampeanas (Dávila et al 2012) (Fig. 1B).…”

“…1B). It is an intermontane hydrological system of about 10,000 km 2 , where the presence of a tangential fluvial system (Colorado River) gives it a more complex character (Vervoorst 1954;Sosic 1973;Morlans 1995;Zarantonello and Mamani 1999;Alonso 2006;Dávila et al 2012). This basin is the groundwater discharge area of an important hydrographic network, making its aquifers valuable resources (Sosic 1973).…”