Bannock Basin, Sirte Abyssal Plain and Conrad Spur: structural relationships between Mediterranean Ridge and its western
- PDF / 3,065,664 Bytes
- 32 Pages / 595.276 x 790.866 pts Page_size
- 14 Downloads / 224 Views
ORIGINAL RESEARCH PAPER
Bannock Basin, Sirte Abyssal Plain and Conrad Spur: structural relationships between Mediterranean Ridge and its western foreland and implications on the character of the accretionary complex (eastern Mediterranean) W. Hieke • A. Camerlenghi • M. B. Cita • G. A. Dehghani • N. Fusi • H. B. Hirschleber L. Mirabile • C. Mu¨ller • A. Polonia
•
Received: 28 July 2008 / Accepted: 6 October 2009 / Published online: 28 November 2009 Springer Science+Business Media B.V. 2009
Abstract In previous publications, the relationship between the Sirte Abyssal Plain as foreland and the Mediterranean Ridge as accretionary complex was considered to be simple: the foreland is undeformed, the accretionary complex consumes the foreland, the Messinian evaporites control the internal structure of the growing complex. The compilation of our own and published data results in a more complex tectonic pattern and a new geodynamic interpretation. The Sirte Abyssal Plain is imprinted by extensional tectonics which originated independently from and prior to the approaching process of accretion. The structural setting of the pre-Messinian and Messinian Sirte Abyssal Plain is responsible for the highly variable thickness of Messinian evaporites. The foreland setting in the Sirte Abyssal Plain also controls the internal structure of the Mediterranean Ridge, at least between the deformation front and Bannock Basin, following sediment deformation within the accretionary wedge with a dominating inherited SW-NE
orientation. The taper angle of the post-Messinian Mediterranean Ridge is unusually small compared with other accretionary wedges. In the studied area, within a distance of about 45 km from the deformation front, there is no appreciable dip in the de´collement. Therefore, the slope of the outer 45 km of the Mediterranean Ridge is considered to be caused only by gravitational spreading of Messinian evaporites deposited on the slope of pre-Messinian accretionary wedge. As a consequence, the Mediterranean Ridge underlying such slope is interpreted to belong to the foreland. The allochthonous evaporites overlie autochthonous evaporites of the Sirte Abyssal Plain. The NE-dipping de´collement (and thus of the true tectonically driven deformation front) is expected to initiate at about the present position of Bannock Basin. The Sirte Abyssal Plain, the adjacent Cyrene Seamount and neighbouring seafloor relief on the African continental margin are considered to be the product of tectonic segmentation of the continental crust.
L. Mirabile—deceased. W. Hieke (&) Lehrstuhl fu¨r Ingenieurgeologie (formerly: Lehrstuhl fu¨r Allgemeine, Angewandte und Ingenieur-Geologie), Technische Universita¨t Mu¨nchen, Arcisstr. 21, 80290 Mu¨nchen, Germany e-mail: [email protected] A. Camerlenghi ICREA c/o Departament d’Estratigrafia, Paleontologia i Geocie`ncies Marines, Facultat de Geologia, Universitat de Barcelona, C/Martı´ i Franque`s, s/n, 08028 Barcelona, Spain M. B. Cita Dipartimento di Scienze della Terra ,,Ardito Desio’’, Universita`
Data Loading...
