3D tectonostratigraphic analysis of the Messinian evaporites in the Levant Basin, Eastern Mediterranean

Doctoral thesis English OPEN
Bertoni, Claudia.
  • Subject: QE

This thesis uses industry seismic (3D and 2D) and well data to investigate the depositional and deformational processes of the Messinian evaporites in the Levant Basin, Eastern Mediterranean. Detailed interpretation of the geometry, structural and stratigraphic context of the evaporites has been undertaken in order to improve our understanding of the events occurring during the Messinian Salinity Crisis in the region. The Messinian evaporites form a wedge up to 1.8km thick that pinches out towards the continental margin, where they pass laterally to a prominent erosional surface. The 3D seismic data have allowed the complete basinal evaporitic series to be imaged in three dimensions for the first time. Investigations showed that clastic bodies and focused incisional pattern developed at their base. The internal part of the evaporites is composed of parallel and continuous seismic reflections, alternating with transparent seismic facies. These internal reflections are truncated at the top of the Messinian evaporites, against a widespread erosional unconformity. The analysis of the 2D seismic data permitted the connection of these morphological features with a regional system of canyons, developed on the Levant continental margin since the Oligocene. The canyons acted during the Messinian Salinity Crisis as clastic fairways, erosional loci and depocentres for the evaporites. The morpho-structural observations collected have been compared to the pre- and post-evaporitic setting, in order to infer the depositional environment and post-depositional behaviour of the evaporites. Relative sea-level changes in the basin have been interpreted in relation with two major erosional events developed at the base and at the top of the evaporites. Finally, the three-dimensional analysis also allowed an early (Messinian) stage of deformation of the evaporites to be identified, and the discovery of the occurrence of evaporite dissolution during the Pliocene.
  • References (38)
    38 references, page 1 of 4

    2. Controls on the architecture o f the Messinian evaporites................................ 2 - 1 2.1 A bstract...........................................................................................................................2 - 1 2.2 Introduction.................................................................................................................... 2 -2 2.3 Geological setting......................................................................................................... 2 - 5 2.4 M ethodology..................................................................................................................2 - 8 2.5 Seismic stratigraphy......................................................................................................2 - 6 2.5.1 Unit 1 (Late Cretaceous - late M iocene) 2 - 10 2.5.2 Unit 2 (Messinian evaporites) 2 - 10 2.5.3 Unit 3 (Pliocene to Recent) 2 - 13 2.6 Interpretation o f tectonic and topographic controls 2 - 13 2.6.1 Time-thickness o f Unit 2 2 - 15 2.6.2 Morpho-structural analysis 2 - 20 2.6.2.1 Tectonic structures 2 - 20 2.6.2.2 Geomorphological features 2 - 25 2.7 Discussion 2 - 29 2.7.1 Summary o f the main observations 2 - 29 2.7.2 Linear edge o f evaporites 2 - 30 2.7.3 Salients and embayments 2 - 31 2.7.4 Implications for the MSC....................................................................................2 - 32 2.8 Summary and conclusions 2 - 35

    3. C lastic system s in the M essinian evaporites......................................... 3 - 1 3.1 A bstract 3 - 1 3.2 Introduction 3 - 2 3.3 Geological setting 3 - 4 3.4 Seismic analysis 3 - 4 3.4.1 Detailed 3D seismic description o f HAB1 3 - 6 3.5 Interpretation 3- 19 3.6 D iscussion....................................................................................................................3- 21 3.6.1 Distribution o f clastic sediments within the Messinian evaporites 3- 21 3.6.2 Depositional environment - submarine or subaerial? 3- 22 3.6.3 Sea-level position................................................................................................. 3- 25 3.7 Conclusions 3- 26

    4. U nconform ity at the top of the M essinian evaporites...........................................4 - 1 4.1 A bstract 4 - 1 4.2 Introduction 4 - 2 4.3 Geological background 4 - 3 4.4 Dataset and methodology 4 - 5 4.5 Seismic stratigraphy o f the Messinian evaporites 4 - 6 4.6 Geometry o f the evaporitic u n it 4 - 11 4.6.1 Geometry o f the intra-evaporitic horizons 4 - 11 4.6.2 Intra-evaporitic seismic packages 4 - 18 4.6.3 Structural deformation o f the intra-evaporitic horizons 4 - 20 4.7 Interpretation 4 - 21 4.7.1 Intra-evaporitic deform ation 4 - 21 4.7.2 Structural deformation o f the intra-evaporitic horizons 4 - 22 4.8 Discussion 4 - 25 4.8.1 Depositional geometry o f the Messinian evaporites 4 - 25 4.8.2 Mechanism o f structural deformation 4 - 28 4.8.3 Implications for the Messinian erosional events in the Mediterranean Basin..... ............................................................................................................................................ .4-29 4.9 Conclusions 4 - 31

    5. Dissolution stru ctures in the M essinian evaporites 5 - 1 5.1 A bstract 5 - 1 5.2 Introduction 5 - 2 5.3 Regional framework 5 - 3 5.4 Dataset and methodology 5 - 5 5.5 Seismic stratigraphic fram ework................................................................................ 5 - 7 5.5.1 Unit 1 ...................................................................................................................... 5 . 7 5.5.2 Unit 2 5 - \ \ 5.5.2.1 Well calibration o f Unit 2 5 - 11 5.5.3 Unit 3 5 - 13 5.6 Description o f the circular structures 5 - 13 5.6.1 General features 5 - 13 5.6.2 Circular structure CS-1: detailed 3D seismic interpretation 5 - 18 5.6.2.1 Morphology 5 - 18 5.6.2.2 Stratigraphic architecture 5 - 19 5.6.2.3 Structural analysis 5 - 20 5.6.2.4 Faults 5 - 20 5.6.2.5 Onset and tim ing 5 - 22 5.6.3 Circular structure CS-2 to CS-10: detailed 3Dseismic interpretation 5 - 26 5.7 Discussion 5 - 27 5.7.1 Observations and identification 5 - 27 5.7.2 G enesis 5 - 29 5.7.2.1 Mechanism o f dissolution 5 - 29 5.7.2.2 Origin o f fluid flow 5 - 29 5.8 Conclusions 2 - 35

    7. Conclusions..................................................................................................................... 7 - 1 7.1 General conclusions......................................................................................................7 - I 7.2 Controls on the architecture o f the Messinian evaporites........................................7 - 2 7.3 Clastic deposits at the base o f the Messinian evaporites.........................................7 - 3 7.4 Nature o f the top o f the Messinian evaporites.......................................................... 7 - 3 Abdel Aal, A., El Barkooky, E., Gerrits, M., Meyer, H., Schwander, M. & Zaki, H., (2000) Tectonic evolution of the Eastern Mediterranean Basin and its significance for hydrocarbon prospectivity in the ultradeepwater of the Nile Delta. The Leading Edge, 19, 1086-1102.

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