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FRAGILE EARTH: Geological Processes from Global to Local Scales and Associated Hazards (4-7 September 2011)

Paper No. 9
Presentation Time: 15:00

STRUCTURE AND EVOLUTION OF THE COLORADO BASIN, ARGENTINE PASSIVE MARGIN


AUTIN, Julia1, SCHECK-WENDEROTH, Magdalena1, LOEGERING, Markus J.2, ANKA, Zahie3, VALLEJO, Eduardo4, RODRIGUEZ, Jorge F.4, MARCHAL, Denis4, DOMINGUEZ, Fabian4, REICHERT, Christian5 and DI PRIMIO, Rolando3, (1)Section 4.4 Basin Analysis, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg C4, Potsdam, 14473, Germany, (2)Section 4.3 Organic Geochemistry, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, (now at: Fugro Robertson Ltd. Llandudno, LL30 1SA United Kingdom.), Potsdam, 14473, Germany, (3)Section 4.3. Organic Geochemistry, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, 14473, Germany, (4)Petrobras Energía S.A, Buenos Aires, Argentina, (5)Marine Resource Exploration (B1.1), BGR Federal Institute for Geosciences and Natural Resources, Geozentrum Hannover, P.O. Box 51 01 53, Hannover, D-30631, Germany, leni@gfz-potsdam.de

The Argentine margin presents a strong segmentation [e.g. Franke et al., 2007]. We focus on the volcanic segment (between the Salado and Colorado transfer zones), which is characterized by seaward dipping reflectors (SDR) all along the ocean-continent transition [e.g. Gladczenko et al., 1997]. The segment is structured by E-W trending basins, which differs from the South African margin basins and cannot be explained by classical models of rifting. Thus the study of the relationship between the basins and the Argentine margin itself will allow the understanding of their contemporary development. We firstly focus on the Colorado Basin, which is thought to be the conjugate of the well studied Orange Basin at the South African margin.

This work presents results of a combined approach using seismic interpretation and structural, isostatic, gravimetric and thermal modelling highlighting the structure of the crust. The general basin direction is almost orthogonal to the present-day margin trend. The structural interpretation shows two main directions of faulting: margin-parallel faults (~N30°) and rift-parallel faults (~N125°). A specific distribution of the two fault sets is observed: margin-parallel faults are restrained to the most distal part of the margin.

We can recognise 5 main structural parts in the study area. (1) The western segment shows a NNW-SSE trend. (2) The central segment shows a NW-SE trend. (3) The eastern segment presents the thickest syn-rift depocentres (4700 m) with a NW-SE trend. (4) The distal step is bounded by major NE-SW faults and depocentres. (5) The oceanic crust is 6 km-thick and bounded by SDRs corresponding to the Continent-Ocean Boundary.

Starting with a 3D structural model of the basin fill based on seismic and well data the deeper structure of the crust beneath the Colorado Basin can be evaluate using isostasy, gravity and thermal modelling. The evolution of the basin and the subsidence history are strongly linked to the emplacement of a lower crustal body at the base of the crust.

Franke, D., Neben, S., Ladage, S., Schreckenberger, B. and Hinz, K., 2007. Margin segmentation and volcano-tectonic architecture along the volcanic margin off Argentina/Uruguay, South Atlantic. Marine Geology, 244(1-4): 46-67.

Gladczenko, T. P., et al. (1997), South Atlantic volcanic margins Journal of the Geological Society, London 154, 465-470.

Session No. 2

T2D. Evolution of the South Atlantic, Adjacent Continents, and Passive Continental Margins in General
Monday, 5 September 2011: 11:00-17:35
A 125 (Ludwig-Maximilians-Universität München)
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