Petrography and diagenesis of the Middle to Upper Jurassic succession from Sargelu section, northeastern Iraq

Abstract

Petrographic and diagenetic analysis of the Middle-Upper Jurassic successions (Sargelu, Naokelekan, and Barsarin) formations and boundaries between them in the Sargelu area, Kurdistan region, N.E. Iraq was conducted based on the lithologic description, thin section analysis, and scanning electron microscopy. The study aims to define the petrographic components and diagenetic processes that affect the carbonate rocks of Jurassic succession in the studied section. Thirty-eight thin sections have been prepared, with five samples selected using the S.E.M. technique to reveal the petrographic components and diagenetic processes. The Jurassic succession is composed mainly of carbonates (limestone and dolostone) interbedded with shale units. Petrographically, the Sargelu, Naokelekan, and Barsarin formations are composed of skeletal grains (pelagic pelecypods, radiolaria, calcispheres, planktonic and benthonic foraminifera such as miliolid, ostracods, bioclasts, and stromatolites) which are the most common, in addition, non-skeletal grains such as poloids, micritic groundmass, and recrystallized micro spars, Many diagenetic processes affected the studied carbonate rocks such as micritization, dolomitization compaction and stylolite formation, authigenic minerals (pyrite), cementation, neomorphism, dissolution and porosity formation as represented by moldic, vuggy, channel and fracture porosity.

Depositional environment of the late Paleocene-early Eocene Sinjar Formation, Iraq: Implications from facies analysis, mineralogical and geochemical proxies

“…The presence of bioclastic packstone and highly micritized bioclasts and fossil shells along with association of packstone-wackstone rich in milolids and green algae represent a mostly low energy depositional environment with little impact from storm events, such as the back reef flank [ 38 , 40 ]. This facies falls under the FZ7 of [ 31 ] and SMF18 of [ 30 ] and suggests deposition in restricted platform environment.…”