Effective elastic thickness in the Central Andes. Correlation to orogenic deformation styles and lower crust high-gravity anomaly

Abstract

strong spatial correlation with the styles and mechanisms of deformation in the easternmost sector of the Central Andes. In the Santa Bárbara system T e values less than 10 km predominate, whereas in the Subandean system high T e values were observed. Such high values correlate with the orogenic curvature and with an shallower gravity Moho zone, which breaks the regional trend of the Central Andes. This shallower gravity Moho is linked to a high-gravity anomaly located in the east part of the Eastern Cordillera and Subandean system. These results are also correlated with a high-velocity zone in the upper mantle previously found by receiver functions studies. This correlation could indicate changes in the properties of the lower crustal rocks that justify the shallower gravity Moho zone and explain in part the highest T e values.

Crustal and Mantle Structure Beneath the Southern Payenia Volcanic Province Using Gravity and Magnetic Data

“…Working in the wave number domain with module k (Watts, ), a Python code of forward modeling was implemented in order to calculate the effective elastic thickness T e (García et al, , ; Soler, ), where the basins are considered as buried loads using the term ρ t gh − (( ρ c sup − ρ sed ) gh sed ) instead of ρ t gh , when it corresponds. The code requires two inputs: the topography and the complete Bouguer anomaly with the correction of the sedimentary effect for the Neuquén Basin area.…”

“…No significant differences in T e values were found using this range of windows size. A more detail description of the method and code can be found in García et al (). For any particular chosen window several hypothetic values of T e were considered and the respective deflection W local was calculated.…”

“…The forward modeling code used in this work has the advantage of determining the deflection generated by the topographic load of the study area along the x ‐ y plane, where each value of selected T e represents a single and minimum rms. Finally, it is possible to choose a higher resolution window (70–200 km 2 ) looking for a better fit between the deflection of the elastic plate (which is calculated considering the influence of the entire topographic load of the area, even bigger than the interest area) and the inverted gravimetric deflection (García et al, ). Results are described in section and shown in Figure b.…”

GRASS GIS for topographic and geophysical mapping of the Peru-Chile Trench

“…Deep correlation between the geophysical settings and height elevation as effects of topography and geoid on gravity anomalies are reported recently by Pivetta & Braitenberg, (2020). Furthermore, García et al (2018) report example for the mountainous areas of Central Andes with rugged topography of the relief and show correlation between the geoid undulations, orogenic deformation and lower crust high-gravity anomaly, as well as the elastic thickness and heat flow, proving interplay between the geophysical and topographic settings.…”

Bouguer Gravity Anomaly in the Andean Orogenic Belt and its Dynamic Implications for Regional Tectonic Evolution

“…The belt has formed mainly by interactions between the South American and Nazca plates as well as the Antarctic plate (Pardo-Casas and Molnar, 1987). Various aspects of the lithospheric structure of the Andean orogenic belt have been investigated in previous studies, including crustal structure (Gans et al, 2011;Assumpcã o et al, 2013;Heit et al, 2014;Ryan et al, 2016;Sanchez et al, 2017) and Moho depth (ANCORP, 2003;Gans et al, 2011;Ryan et al, 2016;Idá rraga-Garcí a and Vargas, 2017), interpretation of gravity and magnetic anomaly distributions (Alvarez et al, 2012(Alvarez et al, , 2014(Alvarez et al, , 2015Sanchez et al, 2017;Garcia et al, 2018;Meessen et al, 2018;Tamay et al, 2018;Ibarra et al, 2019), P-and S-wave velocities (Vp and Vs) (Gailler et al, 2007;Heit et al, 2008Heit et al, , 2014Bianchi et al, 2013;Chulick et al, 2013;Ward et al, 2013;Liang et al, 2014), and Vp/Vs ratios (Heit et al, 2008(Heit et al, , 2014. Crustal thicknesses in the Andean orogenic belt reach ~75 km in southern Peru and the Bolivian Altiplano, whereas they are close to ~40 km in Ecuador and southern Colombia (Assumpcã o et al, 2013;Chulick et al, 2013).…”