A large-scale paleontological excavation in Lebanon documents terrestrial ecosystem of the Cretaceous

An international team of paleontologists has uncovered a remarkably rich and diverse array of fossils from the Early Cretaceous, in Jezzine, South Lebanon. “It is rare getting a glimpse on the diversity of such an early terrestrial ecosystem for this continental area”, says paleontologist Ninon Robin,  Institute of Natural Sciences.

Alexandra Badila

In the Early Cretaceous period, roughly 145 to 100 million years ago, our planet underwent important changes in its landscapes. Many species that shape the world we know today emerged and radiated from this period, referred to as the Cretaceous Terrestrial Revolution. First, a global warming trend resulted in the appearance of flowering plants and their pollinating insects. Simultaneously, several modern groups of animals appeared and diversified, eventually outnumbering, for some of them, former species. They include freshwater ray-finned fish, birds among other dinosaurs, and modern mammals.

Many regions around the world have provided scientists with extensive documentation on the beginning of this period (-150 to 125 millions years), with terrestrial deposits of exquisite conservation in East (China) and West (Spain, Belgium) Eurasia, America and Antarctica. However, no diverse contribution from the large African realm for such an early period had ever been intensively examined up to this day. Thus, we had yet to explore the types of plants and animals that lived during this critical time in warm, tropical climates. To do so, a team of scientists received the support of the National Geographic Society, that funded their campaign and research.

At the beginning of the Cretaceous, Lebanon was part of the same megacontinent than modern Africa, and was located quite close to the equator. Despite its limited surface, Lebanon happens to be one of the richest countries in terms of fossil content. Lately, the country revealed archives for early Cretaceous continental ecosystems: 130 myo oil shales located in the scenic outcrop of Bkassine, in the Jezzine district, South Lebanon. These sedimentary rocks are formed of thin laminated layers deposited at the bottom of a lake, that preserve a wide variety of ancient life forms. “The Jezzine dysodiles showed similarities to other famous fossil-rich shales of this period, so they promised important excavation outcomes to reveal crucial steps in the evolution of the ecosystems we see today”, according to Robin.

Exceptional diversity and preservation

The excavation in Bkassine that took place last October quickly revealed an exceptionally rich fossil archive. “The quantity and diversity of the fossils upon arriving on site was astonishing.”, says Sébastien Olive, paleontologist at the Institute of Natural Sciences. “We kept finding an impressive number of specimens day after day. This allowed us to be quite selective in the fossils to be conserved for further study.” The specimens uncovered include a large quantity of ray-finned fishes, complete coelacanths, turtles, freshwater gastropods, crutaceans, many insect species, and plants, among which different species of fern, algae, spermatophytes - AKA seed plants, and thousands of fossil feces.

But also remarkable was the excellent shape in which the specimens have remained. Many of them are complete, with almost intact skeletons and, for some, even the promise of fossilized organs. “It’s quite rare to find coelacanth fossils that are still complete.” explains Olive. “We can discern very fine details of animal tissues, like the texture of fish scales for example”, says micro-preparator Nathan Vallée-Gillette, who works on extracting the fossils from their sediments. “Moreover, they make good material to work with since the clay sediments come off quite easily without too much risk of damaging the fossil in the preparation process.”

The shallow lake or swamp-like characteristics of the site, along with the impermeable nature of the shale, is what helped preserve up to the most pristine details of the organisms it contained. “Sites of such exceptional accumulation of diversity and preservation are called “Lagerstätten” - term which we can certainly attribute to the Jezzine dysodiles” explains Vallée Gillette.

Local excavation tools

For the excavations, a surface of about 20 square meters was uncovered with heavy machinery in the pine forests of the scenic outcrop of Bkassine. The team of scientists searched for fossils up to about 5 meters deep into the earth to reach the layers relevant to the period of time studied. Once the heavy work was done, they used manual tools to delicately extract the fossils from the ground.

The paleontologists got creative once it came to splitting the thin sheets of sediment to uncover the fossils they contained. The long blades of Shawarma knives  - the local kebab - proved to be the ideal tool to open up these shale layers.