The Messel Pit (German: Grube Messel) is a disused quarry near the village of Messel, (Landkreis Darmstadt-Dieburg, Hesse) about 35 km (22 mi) southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance. After almost becoming a landfill, strong local resistance eventually stopped these plans, and the Messel Pit was declared a UNESCO World Heritage site on 9 December 1995. Significant scientific discoveries are still being made, and the site has increasingly become a tourism site as well.
History
Brown coal, and later oil shale was actively mined from 1859. The pit first became known for its wealth of fossils around 1900, but serious scientific excavation only started around the 1970s, when falling oil prices made the quarry uneconomical. Commercial oil shale mining ceased in 1971, and a cement factory built in the quarry failed the following year. The land was slotted for use as a landfill, but the plans came to nought, and the Hessian state bought the site in 1991 to secure scientific access. In the few years between the end of mining and 1974, when the state began preparing the site for garbage disposal, amateur collectors were allowed to collect fossils. The amateurs developed the "transfer technique" that enabled them to preserve the fine details of small fossils, the method still employed in preserving the fossils today.
Due to the extraordinary fossils, the pit was declared a UNESCO world heritage site in 1995, the only site to be placed on the list exclusively due to fossils.
Many of the known specimens from the site have come from amateur collectors, and in 1996, an amnesty on previously collected fossils was put in effect, in the hope of getting privately owned collections back into public ownership and available to science.
Depositional characteristics
The current surface of the Messel pit is roughly 60 m below the local land and is about 0.7 km2 (0.27 sq mi) in area. The oil-shale bed originally extended to a depth of 190 m . 47 million years ago in the Eocene when the Messel deposits formed, the area was 10° further south than it is now. The period was very close to the Paleocene–Eocene Thermal Maximum, and the climate and ecology of the site were very different. A large series of lakes, surrounded by lush sub-tropical forests supported an incredible diversity of life. The Messel lake bed was probably a center point for drainage from nearby rivers and creeks.
The pit deposits were formed during the Eocene Epoch of the Paleogene Period about 47 million years ago, based on dating of basalt fragments underlying fossilbearing strata.Oil shale, formed by the slow anoxic deposition of mud and dead vegetation on the lake bed, is the primary rock at the site. Its sediments extend 13 m (43 ft) downward and lie atop an older sandstone foundation. The fossils within the shale show a remarkable clarity and preservation due to the unique depositional characteristics of the lake. The upper stratifications of the lake most certainly supported a variety of organisms, but the bottom was subject to little disturbance by current, spawning a very anoxic environment. This prevented many epifaunal and infaunal species from inhabiting this niche, and thus bioturbation was kept at a minimum. Overturn of the lake layers (caused by seasonal variations) lowered oxygen content near the surface and led to a periodic "die-off" of aquatic species. Combined with a relatively low rate of deposition, 0.1 mm (0.0039 in) per year, this provided a prime environment for the preservation of fauna and flora.
Volcanic gas releases
The area around the Messel Pit is believed to have been geologically and tectonically active during the Eocene. Leading scientists hypothesize that events much like the 1986 volcanic gas releases at Lake Nyos , Africa could account for the large deposition of non-aquatic species. Periodic subsurface shifts possibly released large concentrations of reactive gases (such as carbon dioxide and hydrogen sulfide) into the lake and adjoining ecosystems, killing susceptible organisms. During these releases, birds and bats might have fallen in if near the lake surface, and terrestrials could be overwhelmed when near the lake shore.
Fossils
The Messel Pit provides the best preserved evidence of Geiseltalian flora and fauna so far discovered. Most other sites are lucky to contain partial skeletons, but Messel boasts extensive preservation of structural integrity, even going so far as to preserve the fur, feathers, and "skin shadows" of some species. Unusual preservation has sparked some closely-reasoned interpretations. The symptomatic "dumb-bell"-shaped bite marks on either side of the leaf vein on a fossilised leaf have been identified as the death-grip of a carpenter ant terminally parasitized by the fungus Ophiocordyceps unilateralis, that, apparently then as today, commandeered its behavior, in order to release its spores from a favourable location; it is the earliest concrete sample of fungal behavioural manipulation.
The diversity of species is remarkable partly as a result of the hypothesized periodic gas releases. A brief summary of some of the fossils found at the site follows:
- Early primate fossil with anthropoid (i.e. non-lemuroid) characteristics (discovery made public May 2009).
- Thousands of aquatic and terrestrial insects, some with distinct coloration still preserved
- Innumerable small mammals including pygmy horses, large mice, primates, ground dwellers (hedgehogs, marsupials, pangolins), aardvark relatives, and bats.
- Crocodiles, frogs, turtles, salamanders, and other reptiles or amphibians
- Remains of over 30 distinct plant species, including palm leaves, fruits, pollen, wood, walnuts, and grapevines
Mammals
Darwinius masillae, identified in 2009 as a basal primate
Kopidodon, an extinct arboreal mammal
Leptictidium, an extinct omnivorous hopping mammal (of the leptictid family)
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 scaleless, anteater-like pangolin
Europolemur, a primate
Paroodectes, a primitive carnivorous mammal
Pholidocercus, an early hedgehog
Macrocranion, an early long-tailed hedgehog
Masillamys at the Senckenberg collection
Masillamys, an early rodent
Messelobunodon, an early artiodactyl
Godinotia, a prehistoric lemur or lemur-like prosimian
Birds
Palaeotis, a "proto-ostrich"
Strigogyps sapea (formerly Aenigmavis)
Messelornis, the Messel-bird; a relative of the sunbittern
Masillastega, a freshwater sulid
The Messelasturidae, enigmatic carnivorous birds that looked like a mix between owls and hawks
Palaeoglaux, a primitive owl with enigmatic breast feathers
Paraprefica, an early potoo
Masillaraptor, a primitive falcon
Parargornis, related to the hummingbirds' ancestors
Messelirrisor, tiny hoopoe-like birds
Selmes (an anagram of "Messel"), a coliiform with stubby toes
Gastornis (formerly Diatryma), a large, flightless predatory bird
Reptiles
Asiatosuchus, a large crocodile
Diplocynodon, an alligator
Hassiacosuchus, a durophagous crocodile
Palaeopython, a snake
Turtles
Fish
A bowfin, variously described as Amia (the modern genus) or Cyclurus
Amphiperca, a primitive perch
Palaeoperca, another primitive perch
Atractosteus, a gar
Eel
Insects
Messel giant ant, a giant species of ant
Jewel beetle
Stag beetle
Rove beetle
Access
Exhibits from the pit may be seen in the Messel town museum, the Museum of Hessen in Darmstadt (5 km from Messel) and also the Senckenberg Museum in Frankfurt (some 30 km from Messel). Casual visitors can park close to the pit and walk around 300 m to a viewing platform overlooking the pit. Entrance to the pit is only possible as part of a specially organized tour.
Messel Pit is the richest site in the world for understanding the living environment of the Eocene, between 57 million and 36 million years ago. In particular, it provides unique information about the early stages of the evolution of mammals and includes exceptionally well-preserved mammal fossils, ranging from fully articulated skeletons to the contents of stomachs of animals of this period.
The Messel Pit has provided a wealth of fossils that have greatly increased understanding of the Eocene Age. It is a small site approximately 1,000 m long (north to south) and 700 m wide (east to west).
The Eocene ('dawn of new times') epoch (57-36 million years ago) was a remarkable period in the evolution of life on Earth. This was the time when mammals became firmly established in all the principal land ecosystems. They also reinvaded the seas (e.g. whales) and took to the air (e.g. bats). During this period of geological time, North America, Europe and Asia were in continuous land contact and the partial explanation of current distribution patterns is provided by the Eocene fossil record.
The Messel Pit provides the single best site which contributes to the understanding of the middle part of this period. Messel is also exceptional in the quality of preservation, quantity and diversity of fossils. Messel offers fully articulated skeletons and the outline of the entire body as well as feathers, hairs and stomach contents.
The sediments of the Messel formation lie on deposits of 270-290 million-year-old Red Sandstone and crystalline magmatic primary rock outcrops.
During the Eocene epoch, subsidence along faults in the Earth's crust led to the formation of a lake basin. The gradual subsidence of old sediments resulted in the formation of new sediments above them, and over time immense deposits accumulated. The oil-shale bed at Messel originally extended to a depth of 190 m. The subsidence of the deposits preserved them from erosion. Outcrops of older seams from the Eocene succession are found on the slopes of the pit. The location of the Eocene Lake Messel lay south of its present position. This accounts for the site appearing to have had a tropical to subtropical climate.
The fossils found here are providing a unique insight into an early stage of mammal, evolution when many of the basic steps in diversification were being achieved. But mammals were not the only component of the fauna - birds, reptiles, fish, insects and plant remains all contribute to an extraordinary fossil assemblage.
In terms of fossil localities which provide a window into the Eocene Age, Messel is the best and most productive example discovered to date. In contrast to other fossil sites that are marine, Messel can be considered as the single best 'classic' locality snapshot of life as it was in the Eocene. It has been identified as one of the four most significant fossil sites in the world by several senior palaeontologists.
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