Belemnites and calcareous nannoplankton: Proxy tools for recognising of cryptic Jurassic geological history of Central Europe
Abstrakt
Belemnites and calcareous nannoplankton (which are both stratigraphically and palaeoecologically important groups of organisms) have been used as crucial evidence for exploring an extended timespan of Jurassic sedimentation in the northern part of the Bohemian Massif. Tectonically and fragmentarily preserved Jurassic strata along the Lausitian Fault have long been considered exclusively as belonging to the Callovian through the Kimmeridgian.
Based on a systematic revision of older collections, new sediment sampling and analysing data, the stratigraphic range of Jurassic sedimentation in the northern part of the Bohemian Massif has been extended, at least from the Bajocian until the Tithonian. Belemnite taxa are represented by six species and two taxa identified as Megateuthis cf.
M. elliptica and Cylindroteuthis cf. C. puzosiana (five genera belonging to four families) document a stratigraphic range from the Bajocian (Megateuthis suevica and Megateuthis cf.
M. elliptica) through the Kimmeridgian. Additionally, calcareous nannofossils do not contradict the Bajocian-Kimmeridgian while also proving the Tithonian age.
Moreover, belemnites clearly show the prevailing Tethyan (Belemnopsis fauna) but also Boreal (Cylindroteuthis cf. C. puzosiana) provenance.
Recorded fossils reveal a longer time span of sedimentation than previously known (starting at least in the Bajocian and terminating in the Tithonian), suggesting the existence of a significantly larger sedimentary basins that had been eroded prior to the Cenomanian transgression event (Upper Cretaceous).