Quantification des flux sédimentaires et de la subsidence du bassin ...

tel-00790852, version 1 - 21 Feb 2013
Structure and evolution of the Gulf of Lions : the Sardinia seismic experiment and the GOLD
(Gulf of Lions Drilling) project
D. Aslanian, M. Rabineau, F. Klingelhoefer, M. Moulin, P. Schnurle, A. Gailler, F. Bache, E.
Leroux, C. Gorini, A. Droxler, N. Eguchi, J. Kuroda, K. Alain, F. Roure, B. Haq.
Since the well-known models of McKenzie (1978) and Wernicke (1985), understanding the
formation of passive continental margins, that is to say the way continental lithosphere is thinned
and leads to subsidence, is one of the main challenges in Earth Sciences. These conservational
models, i.e. simple shear, pure shear or polyphase models, which exclude exchanges between lower
continental crust and upper mantle, are usually proposed to explain lithospheric stretching and
consequent crustal thinning of passive continental margins. These models imply huge amount of
horizontal movement, however, these movement are not observed in the field and authors suggested
that lower continental crust may have been removed from its original place and have flowed towards
the middle part of the system (allochthonous domain, part 2 in Figure 1) or/and it may also have
flowed towards both extremities of the system.
Figure 1: Continental crust thinning process: conceptual versus kinematic approaches. Top: Simplified geometries of a
system of conjugate margins. Drawn after the conjugate Angola and Espirito Santo continental passive margins. A)
Conceptual approach (conservational model): The actual area of continental crust is intrinsically strictly equal to the
initial area, the continental crust thinning process can be converted in the horizontal movement. B) Kinematic
Constraints: the horizontal movement is given by precise kinematic reconstruction. A wide thinned basin remains in that
case. The allochthonous domains (part 2) of each margin overlap each other and are not shown on figure B-2. The
quantity of « missing » lower continental crust depends on the nature (lower continental or not) of the allochthonous
domain. After Aslanian & Moulin, GSL, 2012.
Therefore, one of the main impediment to our understanding of margin formation is the unknown
nature of the intermediate domain between the unthinned continental crust and the true oceanic
crust. Another unknown is how do margin evolve from a margin in a high position during all its