Biostratigraphy and palaeoenvironments of the Upper Cretaceous fossil fish Konservat-Lagerstätten of Lebanon

Abstract Cenomanian deposits are well exposed in Lebanon and consist mainly of limestones that covers about 40% of the Lebanese territory. The sedimentary series is rich in fish fossils encountered in three different Cenomanian outcrops: Haqel, Hjoula and Nammoura. These sites are known for the exceptional preservation of their fossil content. However, over time, different authors proposed different ages and stratigraphic relationships.Trying to fill this gap in knowledge, stratigraphic sections were measured, and samples taken from the three outcrops, considering thickness variations and facies changes in the Konservat-Lagerstätten interval. The micropalaeontological inventory focusing on benthic and planktonic foraminifera identified at family and generic level and when possible, specific level is provided. We identified benthic foraminifers (Biokovinidae, Charentiidae, Cuneolinidae, Dicyclinidae, Mayncinidae, Nezzazatidae, Orbitolinidae, Spiroplectaminidae, Gavellinellidae, Alveolinoidea, Hauerinidae, Spiroloculinidae and other Miliolidae). Among the planktonic foraminifers we identified Hedbergellidae (some with costulated test, Globigerinelloididae, Heterohelicidae and Rotaliporidae). Several calcispheres have been identified. Other biogenic components were identified, including rare dasycladalean algae, bryozoans, ostracods, echinoderms and bone debris.Overall, the microfossils indicate a Middle Cenomanian age based on the presence of Conicorbitolina conica and Favusella washitensis present within the Lagerstätten . The macrofossil assemblages found within (echinoids and ammonites), above and/or below (ammonites) the Lagerstätten are surprisingly not in accordance with dating obtained by microfossils, and give a Late Cenomanian age.The analysis of the relationship between the oxygen and carbon isotopes of the three outcrops is presented to follow and interpret the Ocean Anoxic Event 2.The ichthyofauna list is compiled based on fieldwork by one of us (PAS) and literature. The fish assemblage is the most diverse in the Mesozoic in the world. The Haqel and Hjoula sites share approximately half of their species, while the Namoura site shares approximately 20% of its species with the other two localities. The comparison of the Lebanese fish faunas is discussed, as well as the origin of Haqel and Hjoula assemblages. We consider that the geographically restricted sites of Haqel and Hjoula correspond to submerged sinkholes with favorable living conditions in the water column, but anoxic conditions on the bottom that allow the preservation of carcasses, probably killed by algal blooms. The mixing in the same fossil beds of fish species that probably lived in different environments remains an open question.