4ª edición del PhD Student Presentation Award

Hola a todos:
El próximo lunes 19 de Diciembre a las 11:00 h se celebrará en el Salón de Actos del ICTJA-CSIC el 4º PhD Student Presentation Award (PSPA) de nuestro instituto. 

En este mismo blog ya se pueden empezar a leer (y compartir) los resúmenes de las diferentes presentaciones que optan al PSPA de este año. 


A lo largo de esta semana los pósters que se presentan también se irán exponiendo en el pasillo de la planta baja (al lado del Laboratorio Polivalente, el antiguo LARX).

Salud!

2016 PSPA - Juvenal Andrés - Curie-depth and thermal gradient map of the Iberian Peninsula and surrounding areas

The distribution of temperature at depth is a combination of past and present processes such as, collisions, thickening and thinning of the crust or subduction. Furthermore, the thermal structure of an area is dependent on the physical properties of the rocks (e.g. petrology, radiogenic heat production and thermal conductivity), hindering its understanding. The Curie point (CP) is the temperature at which magnetic minerals become paramagnetic. For the upper part of the lithosphere, the most abundant magnetic mineral is the magnetite, which has a CP of 580°C. Therefore, if we can calculate the depth at which we lose the magnetic signal we can get the depth of 580ºC isotherm. 

In this study, we have calculated a complete map of the Curie-Depth Point (CDP) (Fig.1) from a compilation of aeromagnetic data for the Iberian Peninsula and surrounding offshore areas by means of spectral analysis. The final magnetized layer appears on the range of 13 km to 27 km depth below topography onshore and bathimetry offshore. As expected, this isotherm is shallow in offshore zones, where the crust is thinner while in continental areas, the CDP appears deeper. 

We have compared our results with a Moho depth map of the same area. Offshore, the CDP is usually located beneath the Moho which may imply a magnetic upper mantle, partly formed by serpentinites. This serpentinized upper mantle might have played an important role in the evolution of some areas like the Western Mediterranean. On the contrary, for continental areas the CDP is located above the Moho, with NW Iberia featuring the deepest CDP values. We correlate these values with the late orogenic Variscan evolution that led to crustal thinning and intense thermal metamorphism that melted and re-equilibrated the crust. Finally, we have derived a complete map of the thermal gradient of the Iberian Peninsula and offshore areas.

Figure 1. Final distribution of calculated CDP (black dots) overlapped on ETOPO1 with major geological boundaries.

This work is supervised by Ramon Carbonell (ICTJA-CSIC) and Puy Ayarza (USAL). Economic support has been provided through CGL2014-56548-P project funded by the Spanish Ministry of Science and Innovation. We acknowledge GETECH Group Plc. for providing the magnetic data for the study.

2016 PSPA - Mar Moragas Rodriguez - Diapiric architecture controlled by syn- and post-extension prograding sedimentary wedges

Why rocks are not always deformed in the same way? How mountain chains are formed? Why rivers are distributed in specific patterns in a mountain region? How the plate tectonics are deformed in a subduction boundary? Some geological processes are difficult to understand when direct observations are limited or almost impossible to obtain. Some million years is quite a long period to waiting for check how a mountain belt is formed. In the same way, it would be amazing to go deep into the planet to check the subduction of a tectonic plate, but it is impossible for the moment.

In order to reach a better understanding about the earth dynamics, geologists have been using analogue models since the end of the 19th century to simulate geological processes in a more affordable temporal and dimensional scale. In the present work, we have used analogue modelling techniques in order to study the evolution of diapirs.

Diapirs are a type of geological structures formed due to the upward movement of mobile and less dense material (salt or shales) through more brittle rocks. Diapirs can display a large variety of geometries due to different acting parameters. Can sedimentation be one of the major mechanisms controlling the final diapir geometry? The objective of this work is to use analogue models to understand how diapiric structures are influenced by sedimentation. To do so, and according to their physical properties, we used silicone to simulate less dense material constituting diapirs and coloured sand as brittle rocks and sediments. 

To analyse the impact of sedimentation on the evolution of diapirs, we design a set of analogue models with different sedimentation patterns. From all models we highlight the model with homogeneous sedimentation (Model 1 in Figure 1) and the model with a homogeneous sedimentation phase followed by a prograding sedimentation phase, which implies differential sedimentation along the model device (Model 2 in Figure 1). In areas with high sedimentation, diapirs are well-developed with vertical walls as the one shown in Figure 1. Contrarily, the diapiric structures are less developed and remain in an early diapiric phase in areas with low sedimentation. This would be linked to the loading associated to sediments that would cause a major silicone withdrawal from beneath the sedimentary pile towards diapirs in areas with higher sedimentation. This silicone withdrawal is lower in areas with limited sedimentation.

Thus, the comparison among all the models shows that the amount of sedimentation and how and when this sedimentation occurs have a major impact in the final geometry of diapiric structures. Applying the knowledge obtained from our models to real diapiric basins, it is possible to understand better the dynamics of salt-related basins and improve the interpretation of the geological history of diapiric structures worldwide.

Figure 1: Top view of models 1 and 2 showing the different sedimentary pattern applied. Sedimentation in model 1 is homogenous along the entire model and model 2 is composed of a first phase of homogeneous sedimentation as model 1 and a second phase with a prograding sedimentation that implies high sedimentation in the right-side part of the model and low sedimentation in the left-side part of the model. Last picture show an example of the resulting diapiric geometry in the high sedimentation area of model 2.

This work is supervised by Jaume Vergés (ICTJA-CSIC) and Thierry Nalpas (Geosciences Rennes, Université Rennes 1). This study is funded by Statoil Research Centre, Bergen (Norway) and by the CSIC-FSE 2007-2013 JAE-DOC postdoctoral research contract (E.S.). Additional funding was provided by the Generalitat de Catalunya (2014SGR251). Special thanks to J.J. Kermarrec and Pascal Rolland from Experimental Tectonics Laboratory of Geosciences Rennes (Université de Rennes 1, France). We are grateful to Statoil for its support and permission to publish this research.