الملخص الإنجليزي
This study presents a detailed analysis of the Lower Cretaceous carbonate
Habshan Formation in Wadi Muaiden, in Jabal Akhdar, Northern Oman. The
analysis encompasses a detailed examination of microfacies, depositional
environment, diagenetic alterations, reservoir quality, and chemostratigraphy.
The exposed Habshan Formation was meticulously measured and logged
based on depositional dip, lithology, bed thickness, fossil content, bed
continuity, and nature of bed contact. Eighty-three whole rock samples were
systematically collected at intervals of fifty centimetres from different
lithofacies and subjected to portable X-ray diffraction analysis. In addition, a
total of 49 thin sections underwent preparation and examination.
Compositional models were established through the enumeration of 300
points in each thin section. This method served to elucidate the texture, fossil
assemblages, and fabric of primary constituents, as well as to identify any
diagenetic alterations. Furthermore, eight whole rock slides were directly
subjected to scanning electron microscopy (SEM) techniques to discern highresolution pore geometry. Eight selected thin sections underwent Energy
Dispersive X-ray Spectroscopy (EDS) analysis for further geochemical
examination to determine the chemical composition of specific parts within the
thin section and to establish cement mineralogy. The findings of integrated
sedimentology, petrography, and geochemical investigation indicated a
variety of microfacies and diagenetic processes that had significant effects on
reservoir quality. A total of seventeen microfacies types were clearly identified
and classified into five facies associations, ranging from the inner to the outer
ramp. lagoon, backshoal, shoal, foreshoal, and offshoal. The Habshan
Formation is represented as a prograding succession of shallowing upward
facies, primarily comprised of oolitic packstones to grainstones with some
bioclasts deposited in a shallow marine environment. The diagenetic
alterations that were observed in the exposed formation include micritization,
calcite cementation, fracturing, compaction, and minor pyritization and
silicification. Diagenetic processes such as cementation of calcite micritization,
and chemical and physical compaction are the main factors leading to reduced
porosity, while processes such as dissolution, open fractures, vugs, and
interparticle contribute to improved porosity. Additionally, elemental
chemostratigraphy integrated with microfacies analysis was employed to
establish a sequence stratigraphic interpretation of the Habshan Formation,
particularly emphasizing the establishment of the sea level curve. Aluminium,
silicon, potassium, and uranium were utilized as elemental proxies to delineate
the transgressive system tract (TST), highstand system tract (HST), and
maximum flooding surfaces (MFS). This study offers a comprehensive
understanding of the Habshan Formation in Wadi Muaiden in Northern Oman,
providing valuable insights into its microfacies, depositional environments,
diagenetic alterations, and elemental chemostratigraphy framework.
