Introduction
The tectonostratigraphic of the south-eastern Gulf of México and surrounding areas is closely related to different geological events (Figure 1) that include the impact of the Chicxulub asteroid at the Cretaceous-Tertiary boundary (K/T boundary). Other important events were the precipitation of evaporites during the middle Jurassic and the main source of rock deposition during the Upper Jurassic (CNH,2015). Intense contraction during Cenozoic times has generated numerous structures that have trapped a good number of hydrocarbon accumulations, such as the Cantarell-Sihil supergiant field.
Regional Geology Review
Along the Campeche sub-basin, most of the shallow structures are associated with salt-tectonics, presenting contractional and extensional deformations which include salt-detached structures, squeezed salt-diapirs, and thrust diapirs (Ysaccis et al., 2018). Padilla y Sánchez (2007; Figure 2) illustrates Neogene saltdetached structures and Chiapas uplift along a NE-SW cross-section running from SW to NE and parallel to Macuspana half-graben. Cantarell-Sihil structure is projected along this cross-section.
Towards the NW, shale-detached structures developed since the Late Miocene are a major characteristic along Mexican Ridges Fold and Thrust Belt. Active extensional and contractional faults have been mapped along this underexplored margin (CNH, 2015; Figure 2) and they are currently under evaluation by PEMEX and international operators.
Across onshore areas, two main deformation fronts have been widely recognized. The oldest one named Zongolica front is part of the Sierra Madre trend, and it was formed during the late Eocene - Early Oligocene contemporaneously to Laramide orogeny. Towards the south, a younger deformation front (Chiapas) is associated with an active orogen that started around the Middle Miocene.
Macuspana and Comalcalco are two major depocenters oriented NE-SW and approximately 600 - 700 kilometers long. These two major structures could have formed in two extensional episodes: Late Miocene - Pliocene and Pliocene - Quaternary (Figure 2). The presence of a salt-related fold-belt (Ysaccis, et al., 2018) towards the northwest, suggests an important salt-withdrawal process that triggered NE-SW extensional faults which delineate Macuspana and Comalcalco troughs. A cross-section orthogonal to both depocenters (CNH, 2015) shown in Figure 3 suggests that salt-withdrawal to the northwest likely started during Late Miocene.
Mitra et al. (2005) suggested around 10 km of shortening along Cantarell-Sihil structure (Thrusts 1 & 2, Figure 3). Normal fault 3 would be contemporaneous to Macuspana extensional episode.
Schematic evolution
3 major deformation events are proposed:
- After Laramide orogeny, a subsequent uplift to the southwest (Zongolica front) triggered saltmobilization between Late Oligocene (?) and Middle Miocene. During this episode, an NW-SE salt-detached fold-belt running parallel to Zongolica's front (red lines in Figure 4a) was formed. Cantarell-Sihil structure should be associated with this deformation stage.
- Chiapas orogeny starting in Middle (?) - Late Miocene is accompanied by salt-withdrawal to the northwest that triggered Macuspana half-graben depocenter (Figure 4b).
- Continuous salt-withdrawal to northwest during Pliocene - Quaternary, is responsible for triggering Comalcalco half-graben depocenter (Figure 4b).
A more complete tectonic evolution analysis must consider the salt-related deformations that occurred during Mesozoic and Paleogene times. Evidence of salt movement such thickness variations underneath the Cantarell-Sihil structure during the Lower Cretaceous (Figure 3) are shown by Mitra et al. (2005). Along Yucatán sub-basin, salt-related structures during Jurassic have been documented by Hudec and Norton (2019).Since there are several different interpretations of the Cantarell-Sihil field structure (timing and tectonics mechanism) in the public domain literature, a thorough analysis with updated seismic data is recommended, as well as new balanced cross-sections of the different possible scenarios.
Conclusions
Neogene's tectonic evolution of the southern Gulf of México (Campeche sub-basin) is associated with intense salt-mobilization, and it can be separated into 3 main episodes:
- Late Oligocene (?) - early Miocene to middle Miocene: salt-rooted thrusts running parallel to the Paleogene Zongolica front that generated a series of northwest-southeast oriented anticlines (i.e., Cantarell-Sihil structure).
- Late Miocene – Pliocene extension: NE-SW Macuspana depocenter.
- Pliocene – Quaternary extension: NE-SW Comalcalco depocenter immediately to west.
These last 2 episodes of extensional deformations are likely triggered by salt withdrawal (“rafting” mechanism?) due to the basin tilting to the northwest. A notorious amount of salt evacuation towards the northwest is responsible for intense salt-related structures (“salt-tectonics”) along deep-water Campeche sub-basin since Miocene times.
Acknowledgments
I´ll like to thank PETRONAS colleagues for fruitful discussions between 2017 and 2020. The ideas presented herein, however, are solely the author’s interpretation.
References
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Hudec, M. and Norton, I. [2019] Upper Jurassic structure and evolution of the Yucatán and ´ Campeche subbasins, southern Gulf of México, AAPG Bulletin, 103 (5), 1133-1151.
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Padilla y Sánchez, R. J. [2007] Evolución geológica del sureste mexicano desde el Mesozoico al presente en el contexto regional del Golfo de México. Boletín de la Sociedad Geológica Mexicana 59, 19–42. doi:10.18268/BSGM2007v59n1a3
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This paper will be published at the 83rd EAGE Annual Conference & Exhibition 2022 In Madrid
