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Silurian graptolites from Bohemia, Czech Republic

Persson, Christian (1999) In Dissertations in Geology at Lund University
Department of Geology
Abstract
The only relatively undisturbed Ordovician to Middle Devonian sequence in the Bohemian Massif is preserved in the central parts of the Prague Basin. This part stretches c. 35 km from Prague in the north towards Zelkovice in the southwest. During Ordovician and Silurian times this area is thought to have been a part of the northern Gondwana margin. The lower Silurian shales were deposited in a tectonically controlled depression on a sediment-starved shelf with about 100-200 m water depth. Marine sedimentation in the Prague Basin started in the Tremadoc and continued to its culmination in mid-Devonian times during the Variscan Orogeny. The lower Silurian in the Prague Basin is composed of a continuous sequence of black shales, rich in fairly... (More)
The only relatively undisturbed Ordovician to Middle Devonian sequence in the Bohemian Massif is preserved in the central parts of the Prague Basin. This part stretches c. 35 km from Prague in the north towards Zelkovice in the southwest. During Ordovician and Silurian times this area is thought to have been a part of the northern Gondwana margin. The lower Silurian shales were deposited in a tectonically controlled depression on a sediment-starved shelf with about 100-200 m water depth. Marine sedimentation in the Prague Basin started in the Tremadoc and continued to its culmination in mid-Devonian times during the Variscan Orogeny. The lower Silurian in the Prague Basin is composed of a continuous sequence of black shales, rich in fairly well preserved and highly diverse graptolite faunas. These faunas were the most cosmopolitan during graptolite evolution.

Graptolites mainly collected by J. C. Moberg in Bohemia in the summer of 1893 have been examined. The collections consist of more than 400 samples of shale and mudstone. 39 species (predominantly monograptids), ranging in age from lower Llandovery to lower Pridoli, have been identified. 16 of these are index graptolites in Bohemia, but since the material was not collected for stratigraphical purposes a proper correlation with other areas is difficult. No obvious trend of size variations between species from different faunas was discovered, though slight differences from coeval assemblages of Britain, Bornholm and Bohemia can be observed. (Less)
Abstract (Swedish)
Populärvetenskaplig sammanfattning: Det Böhmiska Massivet, sydväst om Prag, är rikt på välbevarade och ostörda fossil. Detta område tillhörde superkontinenten Gondwanas norra kontinentalkant för 500- 395 miljoner år sedan under tidsperioderna Ordovicium och Silur. En del av det nuvarande Böhmiska Massivet utgjordes av en sänka där rikligt med sediment och döda organismer deponerades. En stor del av dessa utgjordes av graptoliter (från grekiskan: graptos - att skriva och lith - sten). Dessa kolonilevande filtrerare, som levde planktiskt i marina hav över nästan hela jordklotet, hade en snabb evolution. I och med detta är de utmärkta för åldersbestämning av sedimentära bergarter. På detta sätt kan man se om olika sedimentära bergarter runt... (More)
Populärvetenskaplig sammanfattning: Det Böhmiska Massivet, sydväst om Prag, är rikt på välbevarade och ostörda fossil. Detta område tillhörde superkontinenten Gondwanas norra kontinentalkant för 500- 395 miljoner år sedan under tidsperioderna Ordovicium och Silur. En del av det nuvarande Böhmiska Massivet utgjordes av en sänka där rikligt med sediment och döda organismer deponerades. En stor del av dessa utgjordes av graptoliter (från grekiskan: graptos - att skriva och lith - sten). Dessa kolonilevande filtrerare, som levde planktiskt i marina hav över nästan hela jordklotet, hade en snabb evolution. I och med detta är de utmärkta för åldersbestämning av sedimentära bergarter. På detta sätt kan man se om olika sedimentära bergarter runt om i världen är likåldriga. Det är endast graptolitens koloniskelett (rhabdosom), med filtrerarorganismens boningskammare (theca) som finns bevarat idag. Rhabdosomet är uppbyggt av ett proteinbaserat ämne. De siluriska graptolitfaunorna, som fanns för 435-395 miljoner år sedan, tillhör de mest kosmopolitiska under graptoliternas utveckling, och Pragbassängen i Böhmen är särdeles rik på fina exemplar från denna fossilgrupp. Graptoliterna dog ut för omkring 300 miljoner år sedan i tidsperioden Karbon, men det finns nulevande släktingar i dagens oceaner.

Graptoliter, som insamlades av J. C. Moberg sommaren 1893 i Böhmen, har studerats. Samlingarna består av mer än 400 prover. 39 olika arter har identifierats och 16 av dessa är s k zonfossil, som är särskilt goda för åldersbestämning och jämförelse av sedimentära bergarter. (Less)
Please use this url to cite or link to this publication:
author
Persson, Christian
supervisor
organization
alternative title
Siluriska graptoliter från Böhmen, Tjeckien
year
type
H1 - Master's Degree (One Year)
subject
keywords
Bohemian Massif, Prague Basin, Silurian, graptolites, monograptids, correlation
publication/series
Dissertations in Geology at Lund University
report number
107
language
English
id
2344375
date added to LUP
2012-10-30 15:36:29
date last changed
2012-10-30 15:37:03
@misc{2344375,
  abstract     = {The only relatively undisturbed Ordovician to Middle Devonian sequence in the Bohemian Massif is preserved in the central parts of the Prague Basin. This part stretches c. 35 km from Prague in the north towards Zelkovice in the southwest. During Ordovician and Silurian times this area is thought to have been a part of the northern Gondwana margin. The lower Silurian shales were deposited in a tectonically controlled depression on a sediment-starved shelf with about 100-200 m water depth. Marine sedimentation in the Prague Basin started in the Tremadoc and continued to its culmination in mid-Devonian times during the Variscan Orogeny. The lower Silurian in the Prague Basin is composed of a continuous sequence of black shales, rich in fairly well preserved and highly diverse graptolite faunas. These faunas were the most cosmopolitan during graptolite evolution.

Graptolites mainly collected by J. C. Moberg in Bohemia in the summer of 1893 have been examined. The collections consist of more than 400 samples of shale and mudstone. 39 species (predominantly monograptids), ranging in age from lower Llandovery to lower Pridoli, have been identified. 16 of these are index graptolites in Bohemia, but since the material was not collected for stratigraphical purposes a proper correlation with other areas is difficult. No obvious trend of size variations between species from different faunas was discovered, though slight differences from coeval assemblages of Britain, Bornholm and Bohemia can be observed.},
  author       = {Persson, Christian},
  keyword      = {Bohemian Massif,Prague Basin,Silurian,graptolites,monograptids,correlation},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {Silurian graptolites from Bohemia, Czech Republic},
  year         = {1999},
}