Мессель шұңқыры: ЮНЕСКО мұрасы және ежелгі өсімдіктер мен жануарлардың қазбалары

UNESCO World Heritage Site near Messel, Germany

The Messel pit (link=no) is a disused quarry near the village of Messel (Landkreis Darmstadt Dieburg, Hesse) about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of well preserved fossils of the Messel Formation dating from the middle of the Eocene, it has significant geological and scientific importance. Over 1000 species of plants and animals have been found at the site. 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.

The current surface of the Messel pit is roughly below the local land and is about in area. The oil shale bed originally extended to a depth of 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 Early Eocene Climatic Optimum and the climate and ecology of the site were very different, characterised by a mean annual temperature of 22°C and a large series of maar lakes surrounded by lush sub tropical forests that 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 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 and so the Messel pit represents a Konservat Lagerstätte. 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, per year, this provided a prime environment for the preservation of fauna and flora.

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, Cameroon, could account for the large deposition of non aquatic species (Franzen & Koster, 1994). 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. Since the lake was very deep, animals that fell in it drifted downwards into oxygen and bacteria poor water, where they were preserved remarkably well, being overlaid by successive layers of mud that petrified later, thus producing an aggregation of fossils of exceptional quality, quantity, integrity, and variety. However, other hypotheses have been postulated as well, and have suggested a Cyanobacteria bloom origin resulting in the poisoning of the animals. This last one was considered to be necessary in order to explain the occurrence of excellent fossils throughout the entire sedimentary sequence (Koenigswald & others, 2004).

Describing the Messel Pit Fossil Site as 'richest geosite in the world for understanding the living environment of the Eocene, as it includes exceptionally well preserved fossils', the International Union of Geological Sciences (IUGS) included the site's Eocene record in its list of 100 'geological heritage sites', published in October 2022. The organisation defines an IUGS Geological Heritage Site as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'

Exhibits from the pit may be seen in the Messel town, the fossil Museum in Messel, the Hessisches Landesmuseum in Darmstadt ( from Messel) and also the Senckenberg Museum in Frankfurt am Main (some from Messel). Casual visitors can park close to the pit and walk around to a viewing platform overlooking the pit. Entrance to the pit is only possible as part of a specially organized tour.