The Silurian Period represents a rather unusual period in Earth history. During the last two decades several distinct and rapid changes in the Silurian global carbon cycle have been recognized. These geochemical events were closely linked to major crises in marine ecosystems as well as to palaeoclimatic changes (see Munnecke et al. 2003, Loydell 2007, Calner 2008, for reviews). The largest magnitude perturbation in the Silurian global carbon cycle, named the mid-Ludfordian carbon isotope excursion (CIE) by Kaljo et al. (1997), has been considered also to represent the largest carbon isotope excursion throughout the whole Phanerozoic and the second largest in Earth history (Munnecke et al. 2003). On the other hand, the mid-Ludfordian CIE was preceded only by moderate faunal crises referred to as the Lau conodont Bioevent (Jeppsson 1987), Kozlowskii graptolite Bioevent (Urbanek 1993), and Pentamerid Bioevent (Talent et al. 1993). The mid-Ludfordian CIE and the associated faunal turnover have been documented from many palaeocontinents, in particular from different areas of Baltica (see Kaljo et al.
AbstractThe lower Silurian strata of the Prague Basin, as well as in many other regions, are primarily represented by black shales, with limited to no record of benthic life. In this paper, we describe an exceptional late Aeronian volcanic-carbonate succession from the Hýskov locality near Beroun, which contains a diverse and well-preserved fossil assemblage and specific microfacies features. The studied section is mostly represented by well-washed, poorly sorted skeletal grainstones, rudstones and floatstones along with volcaniclastic material. The environment is interpreted as agitated, above storm wave base, and with rapid sedimentation and burial. The collection of acid-resistant microfossils includes abundant scolecodonts, conodonts and chitinozoans, of which only the chitinozoans have previously been studied. The scolecodonts recovered represent at least 14 polychaete genera and 20 species. The fauna bears a great similarity to the early Silurian assemblages previously reported from Baltica, and some environmentally sensitive species allow constraining the assemblage to shallow-shelf settings. The recovered conodonts similarly show close affinities to Baltic faunas, and suggest a Rhuddanian – Aeronian age for the studied section. The chitinozoan assemblage, containing at least eight species, is dominated by Conochitina, and most likely belongs to the C. alargada Biozone.
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