Integrated carbon isotope stratigraphy and biostratigraphy of Cenomanian to Turonian carbonates from Jordan – An updated age model and sequence stratigraphic correlations with Oman

Abstract

A new integrated age model of the uppermost Albian to Coniacian Ajlun Group in West-Central Jordan is presented based on four complete outcrop sections along a ∼124 km N–S transect. Carbon isotope curves from this work are integrated with published carbon isotope data and constrained by new and existing nannofossil and ammonite biostratigraphy. Key identified carbon isotope events include the Mid-Cenomanian Event 1 (MCE 1), the Oceanic Anoxic Event 2 (OAE 2) at the Cenomanian/Turonian boundary and the Pewsey Event in the middle Turonian. The findings of this study corroborate and revise previous chemostratigraphic definitions in the study area, while also demonstrating a coeval origin of different lithostratigraphic units within the Ajlun Group. On the Arabian Plate scale, a detailed (3rd order) sequence stratigraphic correlation is made between Jordan and time-equivalent strata from the well-studied Natih Formation in Oman. These correlations help to evaluate the relative contributions of eustasy and tectonics on different plate tectonic settings, since the northeastern and eastern margins were heavily influenced by tectonic processes associated with the closure of the Neo-Tethys Ocean. In Oman, the creation of increased accommodation space (ca. 40 m) is observed relative to Jordan commencing in the interval between the MCE 1 and OAE 2. This suggests the onset of tectonic precursor events in Oman during the middle to late Cenomanian interval before the main tectonic phase in the Turonian, resulting in the termination of shallow water carbonate deposition. In contrast, Jordan remained in a largely passive margin setting.