Using basin thermal history to evaluate the role of Miocene–Pliocene flat‐slab subduction in the southern Central Andes (27° S–30° S)

Abstract

Studies in both modern and ancient Cordilleran-type orogenic systems suggest that processes associated with flat-slab subduction control the geological and thermal history of the upper plate; however, these effects prove difficult to deconvolve from processes associated with normal subduction in an active orogenic system. We present new geochronological and thermochronological data from four depositional areas in the western Sierras Pampeanas above the Central Andean flat-slab subduction zone between 27°S and 30°S evaluating the spatial and temporal thermal conditions of the Miocene-Pliocene foreland basin. Our results show that a relatively high late Miocene-early Pliocene geothermal gradient of 25-35°C km À1 was typical of this region. The absence of along-strike geothermal heterogeneities, as would be expected in the case of migrating flat-slab subduction, suggests that either the response of the upper plate to refrigeration may be delayed by several millions of years or that subduction occurred normally throughout this region through the late Miocene. Exhumation of the foreland basin occurred nearly synchronously along strike from 27 to 30°S between ca. 7 Ma and 4 Ma. We propose that coincident flat-slab subduction facilitated this widespread exhumation event. Flexural modelling coupled with geohistory analysis show that dynamic subsidence and/or uplift associated with flat-slab subduction is not required to explain the unique deep and narrow geometry of the foreland basin in the region implying that dynamic processes were a minor component in the creation of accommodation space during Miocene-Pliocene deposition.

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

“…Conversely, the hot sample requires minimum geothermal gradients of 42 °C/km during the Miocene. These values agree more with the values presented by Stevens Goddard and Carrapa () and are higher than the values suggested by Dávila and Carter () (Figure d). In our model, the absence of Cenozoic AHe and AFT ages is explained by the thin sedimentary cover, the lack of basement erosion, and the increase of the AHe system retentivity due to the accumulation of radiation damage during long residence at low temperatures (<120 °C).…”

“…Moreover, these models do not account for possible partial Miocene reheating despite the documented Miocene‐Pliocene strata in the Sierras Pampeanas (Davila et al, ; Schmidt et al, ; Sobel et al, ). Radiation damage controls and Miocene reheating can significantly modify the thermal modeling results, as has been shown here and in previous contributions (Sobel & Strecker, ; Stevens Goddard & Carrapa, ). Additionally, the model presented in Bense et al () implies that the Pampean paleosurfaces formed after the development of the relief without explaining the formation mechanisms.…”

“…(c) Exhumation histories of the Cuevas range calculated from the MMS; details of the calculations are presented in the Text S4 and Table S5. The black boxes denote the thermal gradient estimates in the Sierras Pampeanas from other studies (Dávila & Carter, ; Stevens Goddard et al, ; Stevens Goddard & Carrapa, ). Calculations of the exhumation history and the thermal gradients are discussed in section and presented in detail in Text S3 and Table S5.…”

Effects of Miocene–Pliocene global climate changes on continental sedimentation: A case study from the southern Central Andes

“…Here, paleoclimate proxies confirm that global Miocene-Pliocene climate changes are recorded in the sedimentary record (Latorre et al, 1997;Ruskin and Jordan, 2007;Bywater-Reyes et al, 2010;Amidon et al, 2017). Geochronologic controls make it possible to calculate Miocene-Pliocene sedimentation rates at nine independent depocenters throughout the basin (Beer, 1990;Jordan et al, 1990;Reynolds et al, 1990;Carrapa et al, 2006Carrapa et al, , 2008Levina et al, 2014;Amidon et al, 2016;Stevens Goddard and Carrapa, 2017). Precise constraints on the timing of tectonic forcing, as well as drainage Publisher: GSA Journal: GEOL: Geology DOI:10.1130/G40280.1 reorganization, provide the context to isolate the effects of climatic changes on the sedimentation rate.…”

“…We used published geochronology constraints from magnetostratigraphy (Johnson et al, 1986;Reynolds et al, 1990;Malizia et al, 1995) and U-Pb geochronology (Amidon et al, 2016;Stevens Goddard and Carrapa, 2017) to calculate sedimentation rates from nine depositional areas located between 27°S and 32°S. We used locations within a single connected depocenter (Bermejo foreland basin) in order to avoid possible local structural complexities.…”