And the SPA winners are...

Yesterday (Friday 19th) we announced the 2014 Student Presentation Awards at ICTJA. It was a difficult task, choosing among the 10 top research presentations we received, but the final decision has been:

• Best Oral Presentation for María Jesús Rubio de Inglés, for "Reconstructing the past climate using the lipidic fraction".

• Best Poster Presentation for Jan Globig, for his study on the "African lithosphere: Geoid and elevation constraints on Moho and LAB topography"

Congratulations everyone for the good quality of the presentations!

2014 SPA Contest - Siddique Akhtar Ehsan - From the surface Topography to the Upper mantle beneath Central-Iberian-Zone. The ALCUDIA Seismic Experiments

Seismic (from the Greek word Seismos for “shake, vibration of Earth”) wave is the energy that moves through and around the Earth. The seismic waves are messengers that convey information about the interior of the Earth. They are caused by the sudden break of a rock mass within the Earth or they can also be generated by an explosion. The Earth’s outermost shell contains solid and rocky layer called lithosphere. The lithosphere can be divided into the crust and uppermost mantle. The deep seismic reflection data set provide high quality images of the crust and upper mantle. The seismic experiments are also used in hydrocarbon (Oil/Gas) industry to place key constraints on the subsurface geological structures and composition.

In summer 2007 and 2012, multi-seismic experiments namely ALCUDIA, which include normal incidence and wide-agnle data sets were acquired across the central and southern part of the Iberian Peninsula. The seismic experiments provided a new insight into the structure and nature of the lithosphere beneath these areas. A high quality image, ~230 km long, down to 45 km depth (~15 s TWTT) is provided by the normal incidence data set. Based on the reflectivity characteristics, the image can be divided into an upper and mid-lower crust, ~13 km and ~18 km thick, respectively. The wide-angle seismic transect extended the crustal section towards the north across the Madrid Basin. This, latter data set also sample the CIZ until the CU. This is ~280 km long profile which provides very strong constraints on the distribution of physical properties (P wave and S wave velocities, Poisson's ratio) of the upper lithosphere. The PiP and PmP seismic phases constrain two discontinuities: the brittle to ductile discontinuity at ~13-19 km and the Moho boundary at ~31-35.5 km. 

The normal incidence deep seismic reflection image is shown below. Along the x-axis, top and bottom, are the Common depth point (CDP) locations and distance of the image, respectively. Along the y-axis, is the depth. The crust (~31 km thick) is more reflective than the upper mantle.

(a) Uninterpreted poststack time migrated (15 s) and depth converted section. The black arrows highlight the migration artifacts. (b) The geological cross section along the ALCUDIA normal incidence (NI) deep seismic reflection profile. (c) The suggested interpretation of the migrated and depth converted ALCUDIA-NI profile. The black thick lines have been interpreted as faults and/or major shear zones; the red lines are indicative of the trends of the most prominent reflectivity fabric. A blue line highlights the crust mantle transition. Abbreviations: UC, Upper crust; MC,Middle crust; LC, Lower crust; DL, Decollement level; HW, Hanging wall; FW, Footwall; DLCR, Dense lower crustal reflectivity; DFWR, Dense footwall reflectivity; x, y, z, imbricate thrust systems.

2014 SPA Contest - Lavinia Tunini - Looking at the roof of the world: modelling the lithospheric structure of the Himalayan-Tibetan orogen and the present-day deformation

Hallo! I’m Lavinia Tunini, and I’m in the last year of my PhD in the Institute of Earth Sciences Jaume Almera. Since almost two years I’m studying the lithospheric structure in the Himalaya-Tibetan Plateau, which is the largest orogenic system on Earth. The dramatic global-scale geologic event occurred around 55 million years ago when the northward drifting Indian sub-continent collided against the southern margin of Eurasia plate. Today, India plate is still advancing towards the north-east, bulldozing Eurasia plate at a rate of ~4cm/yr and the Indian lower crust continues to be pushed underneath the Tibetan Plateau. Beside the compressive regime related to the tectonic convergence, stress data show also extensional features in the middle of the Tibetan Plateau and to the east of the eastern Himalaya syntaxis (i.e. India’s eastern indentation). Why? The mechanism is still hotly debated in the scientific community. The removal of the lithospheric root in the north-eastern Tibetan Plateau and changes in the mechanical properties of the lithosphere have been proposed to explain the current deformation patterns and the outstanding elevation of the plateau (around 5000 m). By using a geophysical-petrological method I also find that the north-eastern Tibetan Plateau is underlined by a thinner lithosphere (lithospheric base at ~120 km depth) with respect to its southern sector (lithospheric base at ~280 km depth) (Fig. 1). 
Now, I’m investigating which is the relation between the deep lithospheric structure and the deformation patterns at surface. I’m modelling the whole Central Asia but with a special focus on the eastern and south-eastern sector of the Himalaya-Tibetan region (Fig. 2), which is one of the most active intra-continental areas on Earth. Velocity vectors from GPS data image a sort of glacier-like flow of material around the eastern Himalaya syntaxis, and stress data indicate compression and strike-slip regimes in Burma and Yunnan provinces. In addition, the region is densely populated and the level of seismicity is very high, therefore the study of the present-day deformation is of extreme importance for the area! By using a finite-element method which simulates the Earth’s lithosphere as a thin shell, I’m investigating the mechanism responsible for the observed deformation. The results, so far, suggest that a strong lithosphere can explain the eastward extrusion of material from the eastern Tibetan Plateau. However, the clockwise rotation of the velocity vectors around the syntaxis can be realistically explained only by imposing a weak rheology for the lithospheric mantle, and southward and/or south-westward velocities at the boundary nodes of Sunda-Eurasia border. Is the observed deformation related to a retreat of the suducting slab or to a lower crust channel flow? Work is still in progress...

Figure 1. Location and lithospheric structure of the C-D profile crossing the eastern Himalaya and Tibetan Plateau.

Figure 2. The study region of Central Asia. The numerical model, from the lithospheric (crust + lithospheric mantle) and thermal structure, and by assigning a ductile or brittle behaviour to the lithosphere depending on the temperature, provides surface velocities (green arrows) which are compared with GPS data (blue arrows). We’re trying to explain the clockwise motion of material around the eastern syntaxis in the south-eastern sector of the Himalaya-Tibetan orogen (black squared region).

The study has been supported by ATIZA (CGL2009-09662-BTE), TECLA (CGL2011–26670), Topo-Iberia CSD2006-0004 and TopoMed/GASAM (CGL2008-03474-E/BTE/07-TOPO-EUROPE-FP-006) projects.

 

 

 

2014 SPA Contest - María Jesús Rubio de Inglés - Reconstructing the past climate using the lipidic fraction: insights for the future climate.

If you ignore your past, you’ll jeopardize your future… 

It was one of the useful insights given in Star Wars but, it can also be applied to describe the near-future climate scenarios carried out by prestigious climate organizations, like the Inter-Governamental Panel for the Climate Change (IPCC). The present Global Warming is one of the cutting edge topics that is now focussing many scientists but, are we sure that we have not faced any similar climatic trend in the recent climatic past of the Earth? We can use many natural climatic records, like the sediment records retrieved from lakes, to reconstruct past climate oscillations. My name is Maria Jesus Rubio Inglés and the work I am performing at the Institute of Earth Sciences Jaume Almera (ICTJA-CSIC) for my phD thesis is the reconstruction of climatic history for the last 1000 years recorded in Lake Azul (Azores archipelago, Portugal) sediments using the lipidic fraction. The lipids can be produced by bacteria, archaea, tree leaves, or even humans. Each particular fraction of these lipids have been used to track back changes in environmental (pH, human impact) and climatic (temperature, precipitation) oscillations. The different weight of the hydrogen molecules contained in the leaves wax has been used to infer temporal evolution of the amount of precipitation or its origin. In the work presented for ICTJA student presentation Awards, we have used bacterial and archaea lipidic compounds to reconstruct the past temperature in our study site capturing the widely known global warming the last century (Figure). And last, but not least, we are unraveling when humans arrived to Sao Miguel island by analysing the lipids contained on its faeces. All these studies are allowing us to reconstruct climate, environment and history in our Atlantic island and, therefore, to provide both a wider perspective of the present Global Warming and a guide for the future.
The present work has been funded by the projects PALEONAO and RAPIDNAO

                                                         .