Carbon and oxygen isotope variations of the Middle-Late Triassic Al Aziziyah Formation, northwest Libya

This study presents the δ¹³C and δ¹⁸O records from whole rock samples of the Middle-Late Triassic (Ladinian-Carnian) Al Aziziyah Formation that were deposited on a gently sloping carbonate ramp within the Jifarah Basin of Northwest Libya. The Al Aziziyah Formation consists of gray limestone, dolomite, and dolomitic limestone interbedded with shale. The Ghryan Dome and Kaf Bates sections were sampled and analyzed for carbon and oxygen isotope chemostratigraphy to integrate high-resolution carbon isotope data with an outcrop-based stratigraphy, to provide better age control of the Al Aziziyah Formation. This study also discusses the relation between the facies architecture of the Al Aziziyah Formation and the carbon isotope values. Seven stages of relative sea level rise and fall within the Ghryan Dome were identified based on facies stacking patterns, field observations and carbon stable isotopes. The Al Aziziyah Formation δ¹³C chemostratigraphic curve can be partially correlated with the Triassic global δ¹³C curve. This correlation indicates that the Al Aziziyah Formation was deposited during the Ladinian and early Carnian. No straight-forward relationship is seen between δ¹³C and relative sea level probably because local influences complicated systematic environmental and diagenetic isotopic effects associated with sea level change.