An Early Jurassic (Sinemurian–Toarcian) stratigraphic framework for the occurrence of Organic Matter Preservation Intervals (OMPIs)

Lower Jurassic sedimentary successions in the Atlantic margin basins include several organic-rich intervals, some with source rock potential; time-equivalent units are also identified on- and offshore areas worldwide. Despite decades of research, it is still unclear which mechanisms lead to deposition sediments during Early Jurassic. The objectives this study construct a detailed temporal geographical framework Sinemurian–Toarcian organic matter preservation intervals (OMPIs; subdivided into local, regional, superregional) roughly constrain relationship OMPIs ?13C record. This survey combines an in-depth analysis literature on distribution facies new geochemical studies [total carbon (TOC) pyrolysis] from selected outcrop sections Portugal, Spain, Morocco. Strong local control most Sinemurian suggested. Regionally widespread associated negative values broad Sinemurian–Pliensbachian isotopic trend recorded (including Boundary Event). Pliensbachian expressive bordering proto-Atlantic Ocean often linked positive excursions short-lived warm but defined for Late cool interval. Toarcian superregional pronounced Mesozoic. maximum TOC content occurs (recovery) following shift typically Oceanic Anoxic Event (T-OAE), supporting notion that peak sequestration/ocean anoxia post-dated main phase input atmosphere, as suggested by recent modelling efforts. However, additional predate postdate T-OAE, indicating conditions favouring (increased productivity and/or enhanced preservation) were not restricted T-OAE compilation presented paper demonstrates regional expression record ubiquitous may even be more numerous than Cretaceous. Considering association Sinemurian, Pliensbachian, (not taking account related OMPIs) well-defined excursions, here these hold same relevance secondary OAEs Cretaceous, such Valanginian OAE (Weissert Event), Hauterivian (Faraoni Aptian–Early Albian (OAE 1b cluster).