Speaker: Jeremie Giraud

Date: Thursday 12th of January 2023, 1:15pm.

Abstract:

We present a case study using geological and geophysical data from the Western Pyrenees. We use an inversion algorithm integrating an automated geological modelling component to perform geometrical gravity inversion. Starting from a pre-existing geological model of the study area, we deform it using our inversion algorithm to fit the gravity data while accounting for geological data to maintain geological realism. We then investigate different geological scenarios through the removal or insertion of rock units and consider uncertainties in the recovered geometries using a series of geophysically equivalent models generated with the so-called Hamiltonian null-space shuttles.

The area we consider is located in the subduction zone forming the western Pyrenees across France and Spain in a region centred on the Mauleon basin. The subduction was generated during the Iberian and Eurasian collision, with a probable partial uplift of the upper mantle. Using a geophysical inversion driven approach, we focus on the potential presence of shallow mantle material. We assess the geophysical consistency of different geological and geophysical scenarios using the null-space shuttles to transition between several geophysically valid yet geologically different models. Results corroborate previous hypotheses about the presence of a probable mantle wedge, but suggest that its interpreted geometry may need to be revisited.