The Messel Pit ("Grube Messel") of Germany is regarded amongst the richest fossil exposures providing a snap shot of 48 million years ago during the transition from the Early to Middle Eocene between the Ypresian and Lutetian Ages. The first fossil discovered was a crocodile in 1975.
The Eocene was the second of the three epochs of the Palaeogene Period preceded by the Paleocene Epoch and succeeded by the Oligocene Epoch between 56.0 - 33.9 million years ago during the Cenozoic era.
The term Eocene is derived from the Greek “eos”, for “dawn,” and refers to when the mammals seized the ecological opportunity to occupy and diversify in all the warm land-based ecosystems previously dominated by the now extinct dinosaurs.
The Messel Pit is one of three UNESCO World Heritage Sites including Lorsch Abbey and Roman Limes located in the Bergstraße-Odenwald UNESCO Global Geopark. This is an area of approximately 3,500 km² located between the rivers Rhine, Main, Neckar, and the Odenwald hills.
This is an area known for agriculture, farming and forestry. The Messel Pit is a small abandoned oil shale opencast mine now owned by the Government situated near Darmstadt covering an area of about 40 hectares of bituminous oil shale up to 190 meters thick.
The exceptionally well-preserved fossils of the Messel Pit are from the Eocene Epoch have helped in our understanding into the early stages of mammalian evolution including echolocation from the study of fossil bats.
In 2022 the Messel Pit Fossil Site was named among the “First 100 Geological Heritage Sites” designated by the International Union of Geological Sciences (IUGS).
During the Eocene the Earth experienced an extreme global warming event called the Paleocene-Eocene Thermal Maximum or Initial Eocene Thermal Maximum (PETM or IETM). The temperature gradient from the equator to polar regions was only half that of todays and the oceans were a lot warmer. The climate remained warm through the rest of the Eocene though slow global cooling led to the Pleistocene glaciations.
Images by UNESCO and Limes.Media and Tim Schnarr
Messel Pit was once a lake, called Lake Messel, formed after volcanic activity created a steep sided crater. The surrounding area had numerous lakes bordered by sub-tropical forests. Lake Messel may have been a collecting point for drainage from many of the nearby rivers.
The Messel Pit is one of several Eocene oil shale basins in the middle of Sprendlinger Horst in the north-eastern Upper Rhine Graben. The Sprendlinger Horst is mainly built up by the Hercynian basement, Permian sediments, and volcanic rocks, as well as by several Tertiary alkali basalts and rare Cretaceous trachytes commonly associated with volcanic regions.
A key feature of this area is the Messel Gravity Gradient Zone (MGGZ) a North East 45°striking gravity gradient zone north of a maximum east of Darmstadt. The straight-line gradient zone is indicative of a fault zone indicating that the basins are of tectono-volcanic in origin. It’s along this lineament that five crater-type oil shale sites are located including the Messel Pit.
The Messel lake was inhabited by fish, frogs, salamanders, tortoises, crocodiles, lizards and snakes and living adjacent to the lake were insects, bats, birds and early horses.
The Messel Pit fossils are renowned for the preservation of their “soft parts” of organic structures, hair and features alongside bones and teeth. The complex chemical compounds of the oil shale helped to preserve these fossils and are regarded as “chemical fossils”.
Periodically poisonous volcanic gases would be released from the lake and would unfortunately kill all the animals in the surrounding area. The bodies of these animals would drift down into the oxygen-poor lake to be smothered and preserved by the soft silt sediments of the lake.
Messel Pit fossils include an early or basal primate called Darwinius masillae and other mammals such as a Kopidodon (an extinct arboreal mammal), Leptictidium (an extinct omnivorous hopping mammal), Propalaeotherium (an early relative of horses), Ailuravus (a rodent), Peradectes (a marsupial), Palaeochiropteryx, (a bat), Lesmesodon (a small Creodont), Eomanis (an early pangolin), Eurotamandua (a scale less, anteater-like pangolin), Pholidocercus (an early hedgehog).