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Title: Stratigraphic characterization and evolution of a Mid-tertiary age deep water system, Holok area, SW Gulf of Mexico
Author: Sánchez Hernández, Hilarión
ISNI:       0000 0004 2745 9006
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2013
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The Oligo-Miocene strata of the Holok area in the SW Gulf of Mexico are dominated by turbidite deposits. These sequences are made up importantly of submarine channel deposits that resulted in sequences mainly erosional at the base and more aggradational upward. The systematic analysis of this deep-water succession within a chronostratigraphic framework reveals that the architectural stratigraphy was formed in three main stages. Chattian-Aquitanian mud-rich sedimentary systems consisting of submarine channel complexes with development of levees and crevasse splays developed in a basin floor setting. These were followed by Aquitanian-mid-Burdigalian sand-rich systems with development of straight channel feeders that spread out in form of radial distributary channels that empty their sediment load to form frontal splays. The Late Burdigalian systems are marked by abundant volcanoclastic deposits. Whereas eustatic control was the main driving force for the Chattian-Aquitanian deep-water systems, the sediment supply and tectonic-related margin changes became more influential in the sedimentary cycles of the Burdigalian. The increase of volcanoclastic input in the sediment compositions for the Oligo-Miocene sandstones, demonstrate the progressive influence of an in-board magmatic province that was more evident at about ~18 Ma. Likewise the increase in the sediment grain size, straighter submarine channels, the contemporary 40Ar/39Ar cooling ages obtained for volcanoclastics and some changes in the basin margin morphology confirm the important role of tectonics and sediment supply as controlling factors. These deep-water systems were fed by multiple sediment sources that delineate a proximal sediment catchment zone (200-300 km) and a relatively small river drainage system in the continent. Besides, sediment compositional changes in conjunction with palynological data suggest a progressive climate change to arid in the climate through the Oligo-Miocene that influenced the sediment type delivered. The sand-rich turbidite system of the sequence E (Late Aquitanian) hosts the best hydrocarbon reservoirs to explore. These reservoirs consist of feldespathic litharenites and litharenites that show lack of compaction and lack of cementation. Aditionally, this kind of sandstone enhance its property as hydrocarbon reservoir in the form of amalgamated structureless sandstones that typically form the main channel fills. Geophysical modelling of the seismic response for each group of facies predicts that volcaniclastic-rich sandstones create amplitude anomalies similar to DHI´s. Highly vesicular volcaniclastics in sandstones reduce considerably their bulk density and consequently the acoustic impedance. Therefore, better understanding of the rock physics has revealed the amplitudes to be controlled by the low-density character of the volcaniclastics rather than a hydrocarbon fluid effect. In conclusion, Oligo-Miocene deep-water systems were originally developed under conditions of a passive margin typical of the Gulf of Mexico and then they were progressively influenced by a combination of sediment supply and tectonic activity of an active margin, the Pacific margin. So, this is an example of perturbation of deepwater systems of passive margins by geological processes closely linked to active margins.
Supervisor: Not available Sponsor: Consejo Nacional de Ciencia y Tecnología (Mexico) ; Petróleos Mexicanos
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geology