Eckfelder Maar

from Wikipedia, the free encyclopedia

Coordinates: 50 ° 6 ′ 56 ″  N , 6 ° 49 ′ 7 ″  E

Map: Germany
marker
Eckfelder Maar​
Magnify-clip.png
Germany

The Eckfelder Maar is a former volcanic lake that existed around 44 million years ago during the Middle Eocene and is now located in the southwestern Eifel near Manderscheid . It represents an important fossil deposit, which contains numerous, partly complete fossil remains of the former fauna and flora and which has been scientifically investigated continuously since 1987. The extremely numerous finds enable a very detailed reconstruction of the landscape. The Maar belongs next to the Messel Pit and the Geiseltal to vorrangigsten sites from this geological epoch in Central Europe and around the world.

location

The Eckfelder Maar

The Eckfelder Maar is located in the Eifel and lies east of the Lieser River , a tributary of the Moselle just before the confluence of the Pellenbach , at an altitude of 320 to 395 m above sea level. The eponymous village of Eckfeld is located about 2 km south-east of the site, and to the south-west of Manderscheid . Together with the nearby former volcanoes, the Diatrem Hillscheid and the Hillscheid Basalt, the maar forms the southern edge of the volcanic Hocheifel . This approximately 1800 km² area contains around 400 known eruption centers today, in the actual core area around the Hochkelberg the concentration of volcanoes is highest with a total of 170 to 40 km². The main activity period of these volcanoes dates from the Middle Eocene to the Upper Oligocene from 45 million to 25 million years ago and is related to the activities of the Rhine Trench and the associated uplift of the neighboring deposits of the Paleozoic Era .

geology

The maar of Eckfeld originally reached a diameter of 800 to 1050 m, of which around 460 × 500 m are still preserved today due to intensive erosion of the upper areas. The former crater lake is deepened in marine rocks of the Lower Devonian , which consist of sands and silts . These paleozoic rocks are covered by the red sandstone of the Triassic , which originally formed the edge of a former sea here, but was most likely already eroded at the time the volcanic crater was formed. At present, these Mesozoic deposits can only be found as relics in an elevated position at 460 to 470 m above sea level west of the Lieser, about 4 to 5 km away from today's Eckfelder Maar. At the time the maar was formed, this depression created by the erosion of the red sandstone was filled with weathering residue from the adjacent highlands, which formed from the paleozoic and Mesozoic rocks and mainly comprised clays and silts . Remnants of these sediments can still be found today in individual depressions around the Eckfelder Maar. It is assumed that the surface at that time was also about 470 to 480 m above sea level and that the eruption of the Eckfelder eruption center, which is interpreted as a phreatomagmatic explosion , created a hollow shape that later filled the maar lake. After the lake was silted up, it was then overlaid, especially in the Upper Oligocene , by further deposits in the form of fluvial to limnic sediments, which may have formed under the influence of a current pouring into a nearby sea. It was not until the Pleistocene , around 600,000 years ago, that the Eckfelder Maar was exposed again through further erosive processes, which also resulted in the current relief.

The maar filling is now assigned to the corner field formation , which is at least 123 m thick in the center of the crater. Based on the later removal of the upper areas of the maar filling, an original depth of around 210 m is assumed. The actual lake was possibly 110 to possibly 150 or 170 m deep. At the bottom lie two layers up to 50 m thick, which on the one hand represent a breccia of weathered Devonian rocks (rock zone A), on the other hand it comprises erosion rubble mixed with pyroclasts (rock zone B). Both rock layers have no stratification and were formed by the remains of the crater rim, although they were probably formed during the volcanic eruptions. A layered unit of pyroclasts is deposited on it, which evidently arose during the initial phase of the crater lake, which was formed by inflowing groundwater, under limnic conditions and reached a thickness of 30 m (rock zone C). In a completely limnic environment, finely laminated silts and clays emerged, the lowest part of which (rock zone D1) is still free of organic material. This is followed by organic and therefore fossil-rich, also finely layered, mostly whitish-gray clay layers, which are partially interspersed with thin layers of bitumen and siderite and from which all the fossil finds originate (rock zone D2). These fine deposits, which are between 0.5 mm and 80 cm thick, but are on average less than 5 cm thick, arose during the gradual filling of the crater basin with fine-grained deposits in the water, which made the lake increasingly smaller. In some cases, however, there was also mass slippage of sediment layers ( turbidites ) into the interior of the crater at the edge of the basin , some of which consist of coarse-grained material and locally interrupted the fine stratifications. The entire sediment package of rock zone D is around 50 m thick today, but was originally thought to have been much thicker, with the upper area being eroded by extensive landscape erosion. The Eocene sediments are covered by deposits from the Pleistocene and Holocene .

Finds

The finds from the Eckfelder Maar are characterized by excellent preservation. It includes partly complete remains of the flora and fauna of that time, which are represented by at least 30,000 macro remains . The good conservation of the fossil material, which is evident not only in the form of complete skeletons of vertebrates , but also through the transmission of soft tissue and stomach contents in these as well as the natural colors in insects , is primarily due to the low-oxygen and largely alkaline properties as well as the high Share of electrolytes in the deeper areas of the crater lake, in which the dead organisms had mainly accumulated. These rather hostile conditions prevented a decomposition of the organic material and also ensured that hardly any biological influences ( bioturbation ) disrupted the storage structures and thus an almost ideal state of both the fossils and the fine sediment layers remained. A larger part of isolated bones, teeth or more fragmented material only comes from the slope slides.

flora

In addition to countless pollen and spores of higher land plants and also some shells of algae, there are numerous macroscopic remains of leaves, seeds, fruits and twigs as well as more than 600 fossilized inflorescences. The entire floristic remains comprise more than 16,000 finds. These include ferns and mosses , albeit to a lesser extent. By far the greater part is the angiosperms associate. Among them, especially the walnut family are common, such as relatives of Engelhardia and Oreomunnea , which are now at home in the tropically influenced East Asia or Central America. Furthermore, elm , tea and gelatinous plants as well as rose plants occur in large numbers. Numerous of the fossil finds cannot yet be precisely assigned, but a position in some other plant families needs to be examined more closely, such as the diamond , balsam and elderberry plants .

fauna

Gesomyrmex from the Eckfelder Maar

Invertebrates are by far the most common fauna elements in the Eckfelder Maar. Among these, however, sponges and bog animals are rather rare, whereas snails are more common, which are mainly marsh snails . But they are mostly found crushed in the sediment. The most abundant, however, are the arthropods , especially insects , of which there are more than 5000, often complete impressions, comprising over 145 species. 84% of all finds can be assigned to the beetles , including weevils and long beetles , but also leaf beetles , jewel beetles , click beetles and scarab beetles . The genus Cupes from the group of Cupedidae , which is no longer native to Europe today, occurs with several species. One of the peculiarities of the insect fauna is the first fossil record of bird lice of the genus Megamenopon , which was only 6.7 mm long, but looks similar to those that parasitize on water birds today . She also had the remains of digested feathers in the front third of the abdomen. Equally noteworthy are the remains of bees , which include Protobombus and Elektrapis . Both are closely related to today's honeybees and were originally only known from Baltic amber . Among the ants , mention should be made of the extinct genus Formicidium , the remains of which include winged females and males, with queens reaching wingspans up to 16 cm. There are also several specimens of the genus Gesomyrmex . This representative of ants still lives in the forests of tropical Asia today. The water strider of the genus Gerris has also been identified with some individuals from the nymph stage . Other arthropods, but to a lesser extent, are known from the Eckfelder Maar with crustaceans and spiders .

The most common vertebrates are fish that have been found to have at least 700, mostly complete, skeletons and to which, in numerous cases, remnants of soft tissues are still attached. So far, around five genera have been identified, including mudfish , bonefish and bones, as well as perch-like . Higher vertebrates, on the other hand, are more seldom passed down, some of them also come as isolated skeletal remains from the landslides. Among the amphibians there are as yet unidentified representatives of the frogs , with a complete skeleton also being discovered. Reptiles comprise several groups, with crocodiles having been identified as two to three genera, including Diplocynodon , an armored lizard belonging to the alligators with a partial skeleton consisting of the skull and parts of the musculoskeletal system. Trionyx is in turn a representative of the softshell turtles , which has been handed down through complete back armor and a skull, while there are only individual shell remains of the previously undetermined representatives of the Tabasco turtles . Lizards are known so far only from a few fragments of the lower jaw and tooth remnants, as are the birds , of which wing bones and skulls, but also individual feather prints are available.

Mammals have so far been identified with over 16 genera. Amphiperatherium and Peratherium are to be regarded as representatives of the marsupials , each with a lower jaw fragment . Also largely only dental finds of primates are available, but they include at least four genera, including the small Europolemur , which was previously only known from the Geiseltal . The odd-toed ungulates are quite rich in shape , four genera of the rather small equine species have been handed down, including Eurohippus, the most common representative of this group of mammals from the Messel Pit . The discovery of a complete skeleton of the original horse Propalaeotherium with a head-trunk length of 72 cm, which, in addition to individual remaining soft tissue remnants such as the uterus, also contained a fetus and can thus be regarded as a mare who died during pregnancy, is sensational . This finding is one of the few worldwide that suggest that even the earliest horse representatives only had one foal born as an offspring. At the same time, the skeleton also contained food remains in the form of leaves. The same genus includes a skeleton of a young animal and over a dozen skulls, including a complete one, which is one of the few undamaged specimens that have not been displaced by sediment load. The early tapir-like species such as Hyrachyus and Lophiodon are other odd-toed ungulates. The ungulates are also very rich in shape , but largely only exist with remains of the upper and lower jaws. Amphirhagatherium should be emphasized , which with an estimated body weight of 4 kg was one of the largest cloven-hoofed animals of its time and is a distant relative of today's hippos . Herbertlutzius from the group of the extinct Dichobunidae , which only reached the size of today's hedgehog , represents the smallest, so far known cloven-ungulate, described by means of a piece of lower jaw with part of the rear teeth . Other important members of the ungulates are Haplobunodon and Hyperdichobune . Furthermore, individual remains of rodents , including the modern, large Ailuravus and three partial skeletons of previously unidentified bats, have been found in the Eckfelder Maar .

Dating

For a biostratigraphic age classification of the finds from the Eckfelder Maar mainly the remains of the mammals are used, whereby this takes place via the changes in the tooth morphology of the rodents and ungulates . The character of key fossils include the ungulates Haplobunodon , Hyperdichobune and Gervachoerus as well as the modern rodent Ailuravus , but also the equine relative Paraplagiolophus . All of these animals suggest that the findings of the Maarsee are local stratigraphically in the Upper Geiseltalium , named after the important fossil site of the Geiseltal in Saxony-Anhalt , and are therefore between 43 and 44 million years old. This means that the Eckfelder finds can be regarded as about the same age as those of the upper horizons of the Geiseltal and are younger than the lower find areas and the extremely rich Messel Pit . The Geiseltalium in turn belongs to the middle section of the chronostratigraphic level Lutetium , which in turn represents the Middle Eocene . Using radiometric studies using the argon-argon dating lying to the finely layered clays under the (rock zone D) pyroclastic (rock zone C) was determined an absolute age of 44.3 million years ago. These age data on the one hand very well confirm the biostratigraphically determined assignment of the corner fields maar, on the other hand they also represent the maximum age of the corner fields fossil finds.

Landscape reconstruction

The results so far make it possible to reconstruct the former landscape around the Eckfelder Maar. As a fringe seems submerged grown aquatic plants to have been not trained, nor a swampy shore area. The fact that the slopes of the Maarsee were relatively steep and unstable can be seen from the findings of the climbing fern Lygodium , as well as from light-loving plants such as Comptonia and Ephedra . Around the maar there was a dense forest, which consisted of a high proportion of walnuts, but also of palm trees and occasional conifers . Here, too, climbing plants and light-loving plants indicate the presence of scattered clearings. Larger mammals in particular speak against larger areas of open land. The pair and odd- toed ungulates that occur each have a distinctly bunodontic posterior dentition, which speaks for a predominantly fruit- to leaf-rich diet, just as the primates suggest a wooded landscape. Overall, the Middle Eocene period in Central Europe was characterized by a tropical, warm and humid climate, but in contrast to the sites of the Messel mine and the lower layers of the Geiseltal, the annual average temperature at the Eckfelder Maar was already 2 to 3 ° C lower. There are individual differences, especially to the Geiseltal, because at that time it was very close to the coast and characterized by a heavily muddy landscape, while the Eckfelder Maar was far from the sea coast at that time at an altitude of around 480 m.

research

Excavations in the Eckfelder Maar

The exploration of the Eckfelder Maar goes back to the end of the first half of the 19th century, as early as 1839 small outcrops of a local lignite were exploited, the existence of white, clayey deposits ( kaolinite ) was known even earlier . The first finds were made by CO Weber, who wrote a description of fossilized leaves in 1853 and, by comparing them with other fossil sites known at the time, recognized the tertiary age of these fossils. However, the finds were quickly forgotten and only over 100 years later, in 1959, were pollen-analytical comparisons with other sites made. However, it was not until the 1970s and 1980s that the corner fields reached full scientific awareness, when the structure of the subsurface was researched with the help of geological drilling and the existence of a former maar was recognized on the basis of pyroclastic deposits around 50 m deep . Scientific excavations have been taking place almost every year since 1987, coordinated by the Mainz Natural History Museum in collaboration with the State Collection for Natural History of Rhineland-Palatinate , and numerous scientists around the world are involved in their evaluations. More than 400 m² have been developed so far, which is located in the northwest of the interior of the crater.

Individual evidence

  1. ↑ Barbara Den Brok: Petrography and geochemistry of the Eckfelder Maar and von Hillscheid and the integration into the Hocheifel volcanism. Johannes Gutenberg University, Mainz 2000.
  2. ^ Herbert Lutz, Franz-Otto Neuffer: A Climatic Archive with Hide and Hair. In: German Research. 2-3, 2001, pp. 8-11.
  3. ↑ a b c d e f Herbert Frankenhäuser, Werner Löhnertz, Jens L. Franzen, Uwe Kaufluss, Martin Koziol Herbert Lutz, Dieter F. Mertz, Jens Mingram, Torsten Wappler, Volker Wilde: The Eckfelder Maar in the Vulkaneifel - window in one offshore habitat 44 million years ago. In: Mainz Natural Science Archive. 47, 2009, pp. 263-324.
  4. ↑ a b c d e f g Herbert Lutz, Uwe Kaufluss, Torsten Wappler, Werner Löhnertz, Volker Wilde, Dieter F. Mertz, Jens Mingram, Jens L. Franzen, Herbert Frankenhäuser, Martin Koziol: Eckfeld Maar: Window into an Eocene Terrestrial Habitat in Central Europe. In: Acta Geologica Sinica. 84 (2), 2010, pp. 984-1009.
  5. ↑ a b c Markus Sachse: A remarkable fossiliferous mass flow deposit in the Eocene Eckfeld Maar (Germany) —sedimentological, taphonomical, and palaeoecological considerations. In: Facies. 51, 2005, pp. 173-184.
  6. ↑ Volker Bullwinkel, Walter Riegel: The Laminated Lake Sediments of the Eckfeld Maar (Middle Eocene, Germany): Types of Stratification and Role of Organic Matter. In: Facies. 45, 2001, pp. 165-176.
  7. ↑ a b c d Herbert Lutz: The Middle-Eocene "Fossil deposit Eckfelder Maar" (Eifel, Germany). In: Kaupia. 2, 1993, pp. 21-25.
  8. ↑ a b Torsten Wappler, Michael S. Engel: The Middle Eocene bee faunas of Eckfeld and Messel, Germany (Hymenoptera: Apoidea). In: Journal of Paleontology. 77 (5), 2003, pp. 908-921.
  9. ↑ Alexander G. Kirejtshuk: Taxonomic Review of Fossil Coleopterous Families (Insecta, Coleoptera). Suborder Archostemata: Superfamilies Coleopseoidea and Cupedoidea. In: Geosciences. 10, 2020, p. 73, doi: 10.3390 / geosciences10020073
  10. ↑ Torsten Wappler, Vincent S. Smith, Robert C. Dalgleish: Scratching an ancient itch: an Eocene bird louse fossil. In: Proceedings of the Royal Society of London B. 271, 2004, pp. S255-S258
  11. ↑ Gennady M. Dlussky, Torsten Wappler, Sonja Wedmann: Fossil ants of the genus GesomyrmexMayr (Hymenoptera, Formicidae) from the Eocene of Europe and remarks on the evolution of arboreal ant communities. In: Zootaxa. 2031, 2009, pp. 1-20.
  12. ↑ Torsten Wappler, Nils Moller Andersen: Fossil water striders from the Middle Eocene fossil sites of Eckfeld and Messel, Germany (Hemiptera, Gerromorpha). In: Paleontological Journal. 78 (1), 2004, pp. 41-52.
  13. ↑ a b State Collection for Natural History Rhineland-Palatinate / Natural History Museum Mainz: The Eckfelder Maar . Homepage
  14. ^ Jens Lorenz Franzen: First fossil primates from Eckfeld Maar, Middle Eocene (Eifel, Germany). In: Eclogae Geologicae Helvetiae. 97, 2004, pp. 213-220.
  15. ↑ Jens Lorenz Franzen: A pregnant mare with preserved placenta from the Middle Eocene maar of Eckfeld, Germany. In: Palaeontographica Department A. 278, 2007, pp. 27–35.
  16. ↑ a b Jens Lorenz Franzen: New mammalian finds from the Eocene of the Eckfelder Maar near Manderscheid (Eifel). In: Mainz Natural Science Archive. Supplement 16, 1994, pp. 189-211.
  17. ^ Jens Lorenz Franzen: Correction - Correction Herbertlutzius nomen novum instead of Lutzia Franzen, 1994. In: Mainzer Naturwissenschaftliches Archiv. 47, 2009, pp. 325-326.
  18. ↑ Dieter F. Mertz, Carl C. Swisher III, Jens Lorenz Franzen, Franz-Otto Neuffer, Herbert Lutz: Numerical dating of the Eckfeld maar fossil site, Eifel, Germany: calibration mark for the Eocene time scale. In: Natural Sciences. 8, 2000, pp. 270-274.
  19. ↑ Jörg FW Negendank, Georg Irion, Josef Linden: An Eocene maar near Eckfeld northeast of Manderscheid (SW Eifel). In: Mainz geoscientific communications. 11, 1982, pp. 157-172.

Web links