Diplocraterion

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Partially weathered, but clearly recognizable specimen of Diplocraterion parallelum (center, above the scale) in an outcrop of the Potsdam Sandstone (Cambrian) near Chippewa Bay ( New York )

Diplocraterion ( syn . Corophioides , Diplocraterium , Gabavermis , Polyupsilon ) is a genus of trace fossils (Ichnogenus). These are vertical, U-shaped burial tunnels in the sediment. In addition to the characteristic geometry, the presence of so-called spreading is characteristic. H. of linear structures that run outside and parallel to the actual grave tube and show their previous position in the sediment. Diplocraterion occurs mainly in siliciclastic deposits of various marine milieus from the Lower Cambrian and is considered to be the feeding and habitation of small invertebrates bilateral animals .

etymology

The name "Diplocraterion" is derived from the Greek words διπλόος ( diploos 'double') and κρατηρία ( krateria "bowl, bowl"). He refers to the two relatively close together openings of the grave building on the former sediment surface, which can appear as more or less deep hollows on the weathered layer of sedimentary rock. The name was coined in 1870 by the Swedish geologist Otto Torell in a work on the fossils of the Cambrian of Sweden. Type ichnospezies is parallelum Diplocraterion .

Features and demarcation

Schematic representation of Diplocraterion parallelum . The indicated estuary funnels on the original sediment surface are usually not preserved and are therefore not considered a diagnostic criterion .
This specimen clearly shows the dumbbell shape characteristic of Diplocraterion
StadtmuseumBerlin GeologischeSammlung SM-2014-2649.jpg
Relatively small? Diplocraterion in a sandstone rubble from the Cambrian of Sweden (Pleistocene debris from the island of Rügen). The tracks are cut almost parallel to the former sediment surface (the slightly brownish area in the “upper” area of ​​the piece could represent a stratified area). In most specimens, the blade is probably just as weathered as the duct fillings. The indicative dumbbell shape can only be clearly seen in the example marked in red.

Diplocraterion consists of an open or passively filled, U-shaped grave tube oriented perpendicular to the layer surfaces. The two legs of this grave tube can be parallel or diverge downwards. The walls of the tube (filling) are usually smooth. The spreading can be protrusive (lying above the U-bend and showing a successive downward movement of the same) and / or retrusive (lying below the U-bend and showing a successive upward movement of the same). Since it is a vertical structure, this morphology can only be observed in sections of rock oriented across the strata. On layered surfaces, the track is ideally expressed in the form of a dumbbell-like structure, whereby the two thickened ends of the "dumbbell" are the actual cross-sections of the corridor and the "handle" of the "dumbbell" represents the blade.

The trace genera Arenicolites and Rhizocorallium are also U-shaped grave structures . Rhizocorallium is even a spade structure * , but differs from Diplocraterion in that the structures are not vertical, but either parallel or diagonal to the sediment surface. Arenicolites, on the other hand, is a vertical structure, but differs from Diplocraterion in the lack of spreading. In the vertical cross-sections of the U-piece of the grave tube similar Diplocraterion facilities warehouse strong the cross-sections of the simple horizontal Spreitenbaus Teichichnus . In the case of dumbbell-shaped spills on the undersides of the layers of fine sand or siltstone, it does not necessarily have to be a diplocraterion , but the trace fossil bifungites can also be present. Although it was Bifungites already with Diplocraterion synonymised , but has been identified by studies of vertical gates as spreitenloser, conversely π-shaped building, and thus forms an independent track genre.

* Adolf Seilacher summarizes Rhizocorallium , Diplocraterion and other U-shaped spade structures under the term “Rhizocoralliiden”

Ethology, Producers, and Ichnofacies

Since the Diplocraterion ™ tube is filled mostly passive and the general morphology of the building has no feature to suggest that their producers the sediment has systematically scoured, this trace fossil is considered feeding and housing (Domichnion) of a suspension eater : food particles came on the ground flow into the building, where they were filtered out of the stream by its producer and resident, sitting in the U-piece. Polychaetes , echiurids and / or small crustaceans are assumed to be the producer taxa . A U-shaped vertical spade structure is recently created by the mud shrimp ( Corophium volutator ), but only in muddy substrate.

The leaf surface shows that the Diplocraterion Generating Sets modified its building regularly and the U-piece, each time either put a little deeper (protrusion) or to a slightly higher level shifted (retrusion). This is considered to be an indicator of the sedimentation trend in the deposit space. Assuming that the Diplocraterion Generating Sets always kept the same distance from the former sediment surface, the sea floor must therefore a protrusive Spreite from permanent erosion resulting in the deposition space, a retrusive Spreite whereas the result of continuous accumulation of sediment in the deposition space. A blade that is both protrusive and retrusive (“ Diplocraterion yoyo ”) indicated changing sedimentation trends .

Diplocraterion is a typical trace fossil of phanerozoic sandstones of the flat shelf, in particular of the wave and / or tide-influenced offshore area , but also of Tempestites deposited further from the coast . The trace in deep marine deposits ( turbidites ) is less common . It has also been demonstrated in a brackish and even limnic-fluvial milieu. As an element of the Skolithos - and Glossifungites -Ichnofacies Diplocraterion is typically associated with traces such as Skolithos and Arenicolites or (also) Rhizocorallium and Thalassinoides . Although these Ichnofacies are generally considered to be an indicator of the marine environment, the entire sedimentological findings must always be taken into account when interpreting the deposit area. Sun can be found in certain layers of the early Cretaceous siliciclastic the Hasandong lineup (South Korea), although the traces Diplocraterion luniforme and Skolithos sp., But u. a. also shells of freshwater mussels, petrified tree stumps and fossil dry cracks , which are relatively clear indications of a continental deposit area.

" Gabavermis "

Detail of the holotype of " Gabavermis annulatus ", with clearly recognizable segmentation and "warts", both explainable as parts of a retrusive specimen of the Ichotaxon Diplocraterion cf. parallelum .

In 1985 one took sediment collector on the beach of Hjerpsted ( Danish-Slesvig North Sea coast) a sandstone boulders, whose origin probably lies in the Cambrian of southern Sweden. The for scientific work to the Society for attachment customer passed piece shows a structure at that time as a trace fossil Skolithos was determined, with part interpreted this structure as the track generator and 1989 under the name annulatus Skolithos as " body fossil of a suspected annelids " described was. The segmentation of the partial structure (hence the species epithet "annulatus") and the presence of "wart-like structures" on the surface of the partial structure were considered to be evidence of its nature as a body fossil . Since Skolithos, as Ichnogenus, is not allowed to take in any body fossil species and the binomial “ Skolithos annulatus ” had already been assigned for another trace fossil in the 1970s, the genus Gabavermis was subsequently established.

Already in the first description, but was in a commentary pointed out that the " preservation weichhäutiger organisms in clastic rocks [...] a rare stroke of luck [is] , which is all the more rare, the coarser the sediment is ," and " that an oversized Random would be if your colleague actually found a body fossil. “ †  ‡ Later investigations, both on casts and on the original of the holotype of“ Skolithos annulatus ”showed that it is probably a specimen of the trace fossil Diplocraterion parallelum , which was misinterpreted due to the fact that the piece was severely unrolled. The segmented substructure is therefore not a fossilized annelid, but a "weathered part of the spread" of the living and eating structure. As early as 1989, a “mechanical-chemical” weathering and / or erosion phenomenon was considered for the development of the “warts” on the Spreite † . Later it was shown through comparisons with other Diplocraterion buildings in Cambrian till that these "warts" could be remnants of the filled estuary funnels of a retrusive building.

† Gerd Geyer , p. 23 in Troppenz (1989)
‡ for more details on the aspect of the probability of conservation see p. 231 ff. in Hoffmann et al. (2013)

Individual evidence

  1. ↑ a b Abhijit Chakraborty, HN Bhattacharya: Spreiten Burrows: A model based study on Diplocraterion parallelum. Pp. 296-299 in: Sayani Mukhopadhyay, Debdas Ray, Abhik Kundu (Eds.): Geospectrum: Proceedings of UGC Sponsored Conference on Recent Researches in Earth System Science. ACB Publications, Kolkata 2013, ISBN 81-87500-70-0 (full text chapter available on ResearchGate ).
  2. ↑ Otto Torell: Petrificata Suecana Formationis Cambricæ. Lunds Universitets Års-Skrift (Acta Universitatis Lundensis) II: Afdelingen för Mathematik och Naturvetenskap. Vol. 6, No. 8, 1870 ( HathiTrust ), p. 13 .
  3. ↑ Vladimír Šimo, Mário Olšavský: Diplocraterion parallelum Torell, 1870, and other trace fossils from the Lower Triassic succession of the Drienok Nappe in the Western Carpathians, Slovakia. Bulletin of Geosciences. Vol. 82, No. 2, 2007, pp. 165-173, doi: 10.3140 / bull.geosci.2007.02.165 , pp. 167 f.
  4. ↑ a b c Adolf Seilacher: Arthropod Tunnel Systems. In: Trace Fossils Analysis. Springer-Verlag, Berlin / Heidelberg 2007, ISBN 978-3-540-47225-4 , p. 56 ff.
  5. ↑ a b c d René Hoffmann, Johannes Kalbe, Gunther Grimmberger, Steffen Schneider: A new spade construction made of Lower Cambrian attachments or just a special form of conservation of diplocraterion ? Archive for history of history. Vol. 6, No. 4, 2012, pp. 217-238 (full text available online at ResearchGate ); see also the literature cited therein.
  6. ^ A b Adolf Seilacher: Evolution of behavior as expressed in marine trace fossils. Pp. 62-87 in Matthew H. Nitecki, Jennifer A. Kitchell (Eds.): Evolution of Animal Behavior: Paleontological and Field Approaches. Oxford University Press, 1986, ISBN 0-19-504006-6 , pp. 73 ff.
  7. ^ A b Zhang Lijun, Luis A. Buatois, Gabriela Mángano, Qi Yongan, Tai Chao: Middle Cambrian Diplocraterion parallelum from North China: Ethologic significance and facies controls. Bollettino della Società Paleontologica Italiana. Vol. 56, No. 2, 2017, pp. 117–125 ( PDF 3.1 MB); see also the literature cited therein.
  8. ^ Richard G. Bromley: Trace Fossils: Biology, Taphonomy, and Applications. Springer, Berlin / Heidelberg 1999, ISBN 978-3-540-62944-3 , p. 44 f.
  9. ^ Richard G. Bromley: Trace Fossils: Biology, Taphonomy, and Applications. Springer, Berlin / Heidelberg 1999, ISBN 978-3-540-62944-3 , p. 173 f.
  10. ↑ Jeong-Yul Kim, In Sung Paik: Nonmarine Diplocraterion luniforme (Blanckenhorn 1916) from the Hasandong Formation (Cretaceous) of the Jinju area, Korea. Ichnos. Vol. 5, No. 2, 1997, pp. 131-138.
  11. ↑ a b Uwe-M. Troppenz: A new type of Skolithos . Current history. Vol. 5, No. 1, 1989, pp. 21-25 ( PDF 2.9 MB; entire issue).
  12. ↑ a b Mike Reich: Comments on the trace fossil Skolithos annulatus Troppenz, 1989 (Lower Cambrian). Current history. Vol 17, No. 1, 2001, pp. 3-8 (full text available on ResearchGate ).
  13. ↑ Uwe-M. Troppenz: A new generic name for Skolithos annulatus Troppenz, 1989: Gabavermis annulatus. Current history. Vol. 29, No. 4, 2013, pp. 137–146 (full text as JPG scan available on the author's website ( memento of September 29, 2017 in the Internet Archive )).

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