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Cenozoic tectono-sedimentary evolution of the onshore-offshore Tunisian Tell: Implications for oil-gas research

A review of the paleogeographic and tectonic reconstruction of the onshore and offshore Tunisian margin during the Cenozoic is discussed. Five unconformities (A to E) and associated stratigraphic gaps of various vertical extents allow subdivision of the stratigraphic record into depositional units in the following time intervals: (i) Paleocene-Oligocene, (ii) Oligocene-early Aquitanian, (iii) early Aquitanian-Burdigalian, (iv) late Burdigalian-Langhian and (v) Langhian-late Miocene. These intervals can in turn be grouped into four main sedimentary cycles (SC1–SC4) dated to the (1) Paleocene-Oligocene, (2) Oligocene–Burdigalian, (3) Burdigalian-Langhian and (4) Langhian-late Miocene. The oldest depositional unit reflects Eo-Alpine tectonics in the Maghrebian Flysch Basin (MFB); the others are related to the Neo-Alpine syn- and late orogenic tectonic deformation affecting the MFB. The uppermost unit represents post-orogenic deposition. Early Miocene synsedimentary tectonism led to (1) deposition of thick successions owing to a large sediment supply and (2) the occurrence of various tectofacies (unconformities, slumps, mega-turbidites, olistostromes, growth folds, chaotic intervals and heterogenous lithofacies), that all, together with the occurrence of lateral change of facies, clearly indicate non-cyclical sedimentation. During the middle Miocene the Tunisian Tell underwent polyphase thrust tectonism, followed by late Miocene strike-slip deformation with contemporaneous rejuvenation of halokinetics and magmatism (the La Galite Archipelago) that may be traced as far as the Algerian Tell. The margin experienced deep-seated compressional tectonism during the Paleogene, a foreland basin during the early Miocene, and nappe stacking during the middle Miocene, with the occurrence of wedge-top sub-basins. The evolution of the region makes the existence of petroleum resources within either the thrust belt, the foredeep and/or the foreland systems plausible. Oil and/or gas may have been trapped in either i) deep buried allochthonous thrust wedges that are located below the Numidian Nappes, and/or in ii) the imbricate Medjerda Valley domain of the Tell foredeep. The offshore area between northern Tunisia and the La Galite Archipelago may also hold potential for large oil/gas fields, as has been confirmed by exploration of the same overthrust belt in other areas such as in Sicily and the Southern Apennines.

Hypothetical Tunisian margin offshore (revised after Belayouni et al., 2013).

Cite as: Belayouni, H., Guerrera, F., Martín-Martín, M., Tramontana, M., Bullejos, M. (2023). Cenozoic tectono-sedimentary evolution of the onshore-offshore Tunisian Tell: Implications for oil-gas research. Marine and Petroleum Geology 156 (2023) 106426

3D modeling of the stratigraphic and structural architecture of the Crotone basin (southern Italiy) using machie learning with Python

The 3D modeling and representation of geological data have experienced significant growth within last years, due to the use of new technologies derived from advancements in land representation methods. These technologies enable interactive, intuitive and clear geological visualizations. This paper shows how, by using the open-source Python software (operable with a simple internet browser) for machine learning (linear and KNN interpolations), together with Geographic Information Systems (GIS), it is possible to achieve interactive 3D visualizations of geological features in sedimentary basins. This study is performed in the onshore-offshore Crotone area (southern Italy) where a large amount of stratigraphic datasets are available from core perforation and seismic profiles due to the presence of a natural gas extraction field. Thanks to a database of 63 drilling lithologic records and 43 check points obtained from 9 interpreted seismic sections, several 3D HTML models were constructed defining three stratigraphic units (Pre-Messinian, Messinian, and Post-Messinian). An overlap of the Post-Messinian top surface and an erosional truncation of the Messinian top surface toward the N were observed, together with a rising of the Pre-Messinian top surface in the northwestern area. This stratigraphic architecture may indicate differential subsidence and/or uplifting due to syn-sedimentary fault kinematics in the whole studied area. The 3D models with the stratigraphic unit boundary surfaces obtained with KNN interpolation (showing stepped and abrupt edges) allowed the interpretation in terms of structural architecture and synsedimentary fault kinematics. Three main sets of faults were deduced: N–S; NNW-SSE, and ENE-WSW. A minorly represented E-W set was added to the main sets. These faults generated a horsts-grabens structure, and in many cases a determinate set of faults caused a progressive lowering or rising of some areas with an “en echelon” arrangement. According to previous works, these deduced sets of faults (most of them strike-slip faults) have a good agreement with the general structural architecture and defined faults in the area.

Vertical sections obtained with KNN interpolation and exported as png files with sketch index map in the right-up corner. A to E) sections A to E.

Cite as: Falsetta, E., Bullejos, M., Critelli, S. and Martín-Martín M. (2024). 3D modeling of the stratigraphic and structural architecture of the Crotone basin (southern Italy) using machine learning with Python. Marine and Petroleum Geology 164 (2024) 106825. https://doi.org/10.1016/j.marpetgeo.2024.106825