Gravimetric determination of the continental–oceanic boundary of the Argentine continental margin (from 36°S to 50°S)

Abstract

This paper presents the gravimetric analysis together with seismic data as an integral application in order to identify the continental-oceanic crust boundary (COB) of the Argentine continental margin from 36 • S to 50 • S in a continuous way. The gravimetric and seismic data are made up of large grids of data obtained from satellite altimetry and marine research. The methodology consists of three distinct methods: (i) the application of enhancement techniques to gravimetric anomalies, (ii) the calculation of crustal thinning from 3-D gravity inversion modelling of the crust-mantle discontinuity and (iii) 2-D gravimetric modelling supported by multichannel reflection and refraction seismic profiles. In the first method, the analytic signal, Theta map, and tilt angle and its horizontal derivative were applied. In the second method, crustal thickness was obtained as the difference in the depths of the crystalline basement and the crust-mantle discontinuity; the latter was obtained via gravimetric inversion. Finally, 2-D modelling was performed from free-air anomalies in two representative sections by considering as restriction surfaces those coming from the interpretation of seismic data. The results of the joint application of enhancement techniques and 2-D and 3-D modelling have enabled continuous interpretation of the COB. In this study, the COB was determined continuously from the integration of 2-D profiles of the enhancement techniques, taking account of crustal thickness and performing 2-D gravimetric modelling. The modelling technique was complemented by regional studies integrated with multichannel seismic reflection and seismic refraction lines, resulting in consistent enhancement techniques.

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

“…We calculated the five‐dimensional inversion of the regional Bouguer anomaly prolonged 25 km upward, using a five‐layer model with densities increasing with depth, for determining the Moho topography (Figure a; Arecco et al, ; Introcaso, ). We used for the crust a density of δ c = 2,650 kg/m 3 , for the mantle δ m = 3,300 kg/m 3 , and for the transitional zone between the crust and mantle, three layers with increasing densities δ 1 = 2,700 kg/m 3 , δ 2 = 2,800 kg/m 3 , and δ 3 = 2,900 kg/m 3 every 10 km.…”

“…We considered Gardner's empirical velocity‐density relation (Brocher, ; Chulick et al, ; Gardner et al, ) for the Neuquén Basin geological correction and crustal‐mantle densities. Seismic velocities coming from the adjacent Atlantic passive margin were used since no vertical velocity models are available for the Neuquén Basin (Arecco et al, ). Results are described in section and shown in Figure a.…”

Profundidad del Punto de Curie y Flujo Térmico en la Zona de Cuencas Offshore de Argentina

“…Los SDRs se encuentran asociados a anomalías isostáticas y relacionados con la anomalía magnética mesozoica G (Rabinowitz y LaBrecque, 1979) que marcaría el inicio de la transición corteza continental-oceánica (COT, Continental-Oceanic Transition) (Arecco et al, 2016a), la discontinuidad magnética del Colorado limita dos zonas de diferente actividad volcánica. La expresión magnética de la anomalía G se desplaza hacia el este al sur de la discontinuidad y se hace menos intensa (Figura 1) (Ghidella et al, 1995(Ghidella et al, y 2017Arecco et al, 2016aArecco et al, , 2016bArecco et al, y 2018. El borde oceánico-continental (COB, Continental-Oceanic Boundary) (Figuras 1, 2, 6 y 7), es el límite entre el COT y la corteza oceánica, se encuentra sobre el margen oriental de la anomalía magnética G, su existencia y ubicación ha sido determinada a través de estudios sísmicos y gravimétricos (Arecco et al, 2014(Arecco et al, , 2016a(Arecco et al, y 2016bPizarro et al, 2016).…”

“…El borde oceánico-continental (COB, Continental-Oceanic Boundary) (Figuras 1, 2, 6 y 7), es el límite entre el COT y la corteza oceánica, se encuentra sobre el margen oriental de la anomalía magnética G, su existencia y ubicación ha sido determinada a través de estudios sísmicos y gravimétricos (Arecco et al, 2014(Arecco et al, , 2016a(Arecco et al, y 2016bPizarro et al, 2016). Estos métodos geofísicos también se emplearon para confeccionar modelos de profundidad de la discontinuidad corteza-manto superior (Arecco et al, 2016b) y espesores sedimentarios (Pizarro et al, 2016).…”

“…Se utilizaron datos satelitales de topografía del fondo oceánico (batimetría) con una resolución de 15 segundos de arco (Sandwell et al, 2014), disponibles en <http://topex.ucsd.edu/marine_grav/ mar_grav.html>. Lo que representa una resolución promedio para el área de estudio de 460 m en la dirección N-S y 390 m en la dirección E-W. También se contó con modelos gravimétricos 3D de la discontinuidad corteza-manto superior de (Arecco et al, 2016b) y espesores sedimentarios de las cuencas offshore (Pizarro et al, 2016).…”