Role of erosion and isostasy in the Cordillera Blanca uplift: Insights from landscape evolution modeling (northern Peru, Andes)

Abstract

Highlights:-Inversion of the landscape evolution coupled with thermochronological data provides constraints on erosion efficiency factor, uplift rates and geothermal gradient-Isostatic effect of eroding a denser rock mass represent a not negligible contribution to the Cordillera Blanca uplift on a < 5 Ma time scale-Cordillera Blanca drainage divide location is controlled by initial drainage network rather by maximum uplift rates and precipitation distribution

Miocene to modern hydrothermal circulation and high topography during synconvergent extension in the Cordillera Blanca, Peru

“…The CBSZ δ 2 H mica values imply that meteoric water migrated to the BDTZ at depths of 8-13 km (Hughes et al, 2020) during CBSZ formation and resulted in δ 2 H mica values that are inconsistent with hydrogen derived from structurally deep portions of the footwall. Available constraints on CBSZ formation depth, the onset of faulting, and exhumation rates delimit the onset of meteoric water infiltration to between 5.4 Ma and 3.0 Ma (Giovanni et al, 2010;Margirier et al, 2016Margirier et al, , 2018Hughes et al, 2020). Collectively, these relationships suggest that a meteoric-hydrothermal network closely resembling the modern fault and fracture-driven spring network was active during formation of the shear zone mica fish in the Miocene-Pliocene (Fig.…”

“…The CBD has been accommodating synconvergent, orogen-normal extension since ca. 5.4 Ma (Giovanni, 2007;Margirier et al, 2018). CBD-related extension led to net footwall exhumation of 7-14 km (Deverchère et al, 1989;Giovanni et al, 2010;Margirier et al, 2016).…”

“…Exhumation rates along the CBD have been constrained to 1.5-2.5 mm/yr since ca. 5.4 Ma and likely increased after 2 Ma (Margirier et al, 2018). The exhumed footwall consists of Miocene leucogranodiorite intruded into Jurassic and Cretaceous marine sediments and schists (Giovanni, 2007;Margirier et al, 2016).…”

“…Samples >230 m into the footwall at Gatay were 15‰-50‰ higher than samples <130 m but were still less than primary igneous δ 2 H values. This pattern could be explained by juxtaposition of rock-buffered portions of the shear zone against meteorically altered portions during exhumation (e.g., Mulch et al, 2005;Gébelin et al, 2011), changing time-integrated fluid-rock ratios, structural and/or thermal permeability barriers, or the introduction of magmatic fluids during overlap of deformation and batholith crystallization in the central CBSZ (Hayba and Ingebritsen, 1997;Hughes et al, 2019Hughes et al, , 2020Petford and Atherton, 1992;Margirier et al, 2018).…”

Análisis Sedimentológico del Paleolago Jircacocha, Quebrada Cojup, Cordillera Blanca, Perú.

“…In the CB, as valley glaciers passed across the uneven terrain, they carved through the bedrock substrate forming linear valleys and closed topographic depressions that are widespread in this northeast region of the Andes. The form and orientation of the linear valleys is strongly influenced by the tectonic evolution of the region and they lie parallel to E-W trending lineaments that developed perpendicular to the Cordillera Blanca normal fault (Wise and Noble, 2003;Schellart, 2008;Margirier et al, 2018). These lineaments form structural and lithologic weaknesses in the crustal rocks that have been exploited by glacial and fluvial erosion processes and mass wasting.…”