The Abu Dhabi sabkha as a modern analogue to the upper Jurassic Arab C member: A focused comparison of sedimentary evidence

  • Wesley M. Court

Student thesis: Master's Thesis

Abstract

The Abu Dhabi sabkha constitutes the landward portion of the shallow-sloping carbonate ramp situated on the northwestern coast of the United Arab Emirates (UAE). The sabkha sediments in this region are composed of a complex assortment of carbonate, organic, and evaporitic sediments that constitute a shallowing-upward, regressive sabkha sequence. Previous investigations have suggested the employment of the modern sabkha in Abu Dhabi as an analogue for the depositional environment of the Upper Jurassic Arab C member; however, these investigations have generally focused on qualitative interpretations or have lacked adequately constrained data-collection techniques. This study was initiated to address this disconnect between features described from ancient sedimentary sequences and structures observed in the Recent sabkha system. This was achieved by documenting a comprehensive list of sedimentary structures at the Abu Dhabi sabkha surface, in the shallow subsurface, and in the Arab C Member of the Arzanah Field. A comparison of these structures in each setting has revealed that sedimentary features have been heavily influenced by diagenesis: in total, 38 unique structures were observed at the sabkha surface, 13 in the shallow subsurface, and 36 in the Arab C Member of the Arzanah Field. Of the 38 sabkha surface structures, only five are analogous to features the Arab C Member; a further eight structures in the Arab C Member are analogous to structures in the sabkha subsurface. Though limited in number, these genetically related structures confirm the interpretation of a typical regressive sabkha sequence as comprising carbonate packstone to grainstone, overlain by microbially-laminated carbonate, and topped by sulphate units. This stratigraphic unit is common in the Arab C Member of the Arzanah Field, and suggests that the latter was, at least partially, deposited in an environment similar to the modern-day Abu Dhabi sabkha. Much of the remaining Arab C Member does not exhibit structures that are genetically related to the Recent sabkha system observed as part of this study. Instead, these structures display dominantly subaqueous characteristics. As such, it is reasonable to assume that these intervals were deposited in a subtidal lagoon.
Date of Award2016
Original languageAmerican English
SupervisorStephen Lokier (Supervisor)

Keywords

  • Applied sciences
  • Arab formation
  • Evaporite
  • Sabkha
  • Sedimentology
  • Petroleum engineering
  • 0765:Petroleum engineering

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