Subsidence history, crustal deformation & subsurface architecture of Musandam Peninsula & Pabdeh foreland basin

  • Sanat Sakenovich Aidarbayev

Student thesis: Master's Thesis

Abstract

The Musandam Peninsula at the northern end of the Oman Mountains marks a transition zone between the Late Cretaceous oceanic-to-continent collision recorded with the Semail Ophiolite obduction in the Oman Mountains and the Late Tertiary continent-to-continent collision tectonics as seen along the Zagros Fold Belt in southern Iran. Both plate collisions led to an evolution of the Aruma and Zagros foreland basins, respectively. However, in this study we conduct an integrated and thorough research to check the hypothesis that the mid-Tertiary Musandam culmination caused a load on top of the northeastern Arabian plate similar as the two collisional events and, as a result, a minor Pabdeh foreland basin is developed. The research starts from the quantitative evaluation of the subsidence and uplift history of the northeastern Arabian Plate. A modern and powerful basin analysis technique, backstripping, has been applied to seventeen exploration wells located within and around the Musandam Peninsula. The backstripping technique uses biostratigraphic data extracted from the wells and quantitatively determines the depth that basement would be in the absence of subsidence due to water and sediment loading. As a result, the tectonically-driven subsidence/uplift data allowed us to determine at least three major tectonic events since the Late Permian. Firstly, two rift episodes were formed in response to continental breakup and opening of Neo-Tethys Ocean, approximately from ~ 260 to ~ 93 Ma. Heating and stretching of the continental lithosphere at the time of the rifting episodes caused the lithosphere to subside. After these rifting events, the tectonic subsidence curves indicate that the studied area was subjected to two compressional uplift events around ~ 93 (2nd tectonic event) and ~ 25 Ma (3rd). We refer these uplifts to the Late Cretaceous Semail Ophiolite obduction and the Late Tertiary Musandam culmination, respectively, whereby both of them produced lithospheric loads on the top of northeastern Arabian plate and led to the evolution of two foreland basins, Aruma (~ 80 to 25 Ma) and Pabdeh (~ 20 to present day; Figure 27). The research continues with a detailed evaluation of the two rift episodes (1st tectonic event) using a modified McKenzie's uniform stretching model. During the rifting episodes, the northeastern Arabian lithosphere stretched and thinned from 31.2 to 25.45 km to the north (Hagil-1x) while the magnitude of thinning is slightly more in the south (Jiri-1 and SAJAA-1 wells), having 24.8 km thick lithosphere after the two rift episodes. Furthermore, the study constructs a subsurface architecture of the western side of the Musandam Peninsula emphasizing on the Pabdeh foreland basin with help of the seismic interpretation. The available composite seismic lines captured a wedgeshaped geometry of the basin that thickens up to ~ 4 km (2 s TWT) next to Hagab thrust and thins to ~ 800 m (0.4 s TWT) towards the offshore Sharjah (Figure 21 and Figure 22). In terms of structural complexities, the major Hagab thrust forms westverging and east-dipping reverse faults which cause the repetition of stratigraphic layers. The fault tips terminate within the Pabdeh group below the mid-Miocene Unconformity which marks the end of the Musandam Culmination. Moreover, a forward flexure modelling helped to determine the elastic thickness, Te, of the northeastern Arabian lithosphere which predicted the flexural geometry of the Pabdeh foreland basin. Lithospheric flexure calculations could not explain the observed base of the Pabdeh foreland basin using only a surface (topography) load. However, the combination of surface and subsurface (buried) loads could obtain satisfactory fit between the lithosphere flexure with Te of ~ 20–25 km and the observed base of the Pabdeh foreland basin from regional seismic lines and wells. The calculated Te of the Arabian lithosphere beneath the Musandam Peninsula predicted probable shallow but broad shape of the Pabdeh foreland basin. This case puts some confidence to the hypothesis that the Musandam culmination in fact carried all the overlying obducted thrust sheets of Semail in a piggy-back style. With the rise of interest for unconventional resources, we have to better evaluate the essential petroleum system elements during the petroleum exploration phase. Normally, the total subsidence (tectonically-driven plus sediment & water loading) is used to construct the burial history of a basin. Since the backstripping method is able to separate the tectonically-driven subsidence from the total subsidence, we can exactly pinpoint the deposition time of deep-water sediments which can act as a source rock or an impermeable seal. In addition, the tectonic subsidence curve was able to identify precise ages of two uplifts which actually mark the critical timing of potential structural traps and migration pathways for hydrocarbons.
Date of Award2014
Original languageAmerican English
SupervisorMohammed Ali (Supervisor)

Keywords

  • Earth sciences
  • Petroleum Geology
  • 0583:Petroleum Geology

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