Diagenesis of mid-Triassic Ghail formation, Wadi bih, Ras Al Khaimah

Abstract

This study focused on the Early to middle Triassic carbonates of the Ghail Formation outcropping in Ras Al Khaimah (UAE). A range of different methods, which includes outcrop logging, sampling, petrographic description, fluid inclusion and isotopic analyses has been used to describe the main stratigraphic and diagenetic features of the outcropping sedimentary series. In order to understand the depositional environment of the Ghail Formation, petrographic study and depositional fabric analysis were conducted, which showed the Ghail Formation is characterized by lofer cycles, associated with subtidal, intertidal, and supratidal settings. Facies analysis of the Ghail Formation proved cycles, though mostly incomplete, are mainly regressive, shallowing upward. The ideal cyclothems begin with a subtidal bed (Member C), being followed by an intertidal bed (Member B), which is overlain by supratidal bed (Member A). The Fischer plot was generated based on the Lofer cycles, which suggested the Ghail Formation is characterized by third order sealevel cycles. Optical microscopy, Scanning Electron Microscopy (SEM) and Backscattered Electron image (BSE) with Energy-dispersive X-ray spectroscopy (EDS) were used to assess the timing of different diagenetic events (paragenesis), which included dolomitization, physical/chemical compaction, iron oxide formation and calcite cementation. Isotope analysis showed two different generations of dolomites, i.e. low temperature origin and high temperature origin, which could result from sabkha evaporation and burial environment respectively. Fluid inclusion microthermometry in cements filling vugs proved useful to confirm the mesogenetic (burial origin) of the drusy dolomite cements.

Date of Award	Dec 2016
Original language	American English
Supervisor	Andrea Ceriani (Supervisor)