Vol 24, (1986)
Vol 24, (1986)
- Details
- Category: Vol 24, (1986)
Authors: Michal Mergl
Full version (75,068 kB)Abstract: The Leptembolon assemblage has a specific position among the benthic assemblages of the Barrandien Ordovician – its occurrence is linked to red-brown colored sediments [silicites, debris to shale] and it has the same character in the Milín (Upper Tremadok) and Klabava (Arenig) Formations. The appearance of the Leptembolon community is characterized by a number of features: it is primarily a way of preserving fossils; minor crushing of shells, accompanied by selective dissolution of carbonate bowls, completely prevails; the ratio of abdominal and dorsal plates is more or less constant [1:11, the orientation of the plates in the sediment depends mainly on the original sedimentation conditions (flows, washes etc.) High juvenile mortality is typical for the community, although there are interesting deviations (Celdobolus from position H); a large amount of bioturbation, especially vertical, is also typical. The diversity of the community is generally low with the dominance of small inarticulate brachiopods (Conotreta, Leptembolon, Orbithele) and siliceous fungi (Pyritonema); near the boundary between the Milín and Klabava Formation, new elements appear in the community (trilobites, orthid brachiopods, echinoderms, other types of inarticulate brachiopods, ostracods and gastropods), but they quickly disappear and other new genera of brachiopods (Celdobolus) appear again. The community inhabited marine shallow to lagoonal environment. In the uppermost Tremadoc, the community is spread throughout the Prague Basin, with the exception of the eastern surroundings of Prague, in connection with the gradual transgression and expansion of the basin, the community is typically developed in the vicinity of Komárov. The disappearance of the community in this area is related to increased volcanic activity along the Komárov volcanic zone.
