The graptolite, conodont and sedimentary record through the late Ludlow Kozlowskii Event (Silurian) in the shale-dominated succession of Bohemia

Abstract

The shale-dominated hemipelagic succession exposed in the southwestern part of the Prague Synform preserves the most complete Ludfordian graptolite record so far encountered from peri-Gondwanan Europe. Four graptolite biozones -the Neocucullograptus inexpectatus, Nc. kozlowskii, Pseudomonoclimacis latilobus-Slovinograptus balticus and Pristiograptus fragmentalis biozones -are recognized in the middle and late Ludfordian, between the Bohemograptus tenuis Biozone and the base of the Pridoli Series. Conodont occurrences are restricted to scattered limestone beds, but enable tentative integration of the graptolite and conodont biozonal schemes. Particular attention was paid to faunal and sedimentary changes and the carbon isotope record across the middle Ludfordian Kozlowskii extinction Event. The Kozlowskii Event caused the almost simultaneous extinction of graptolites with ventrally curved rhabdosomes. The genera Bohemograptus, Polonograptus and Neocucullograptus, along with Pseudomonoclimacis dalejensis, disappeared from the fossil record. The offshore conodont fauna recorded in the section was not strongly affected and similarly the pelagic orthocerids and nektonic Ceratiocaris passed unaffected through the extinction interval. The abundant and widespread pelagic myodocopid ostracod Entomis, however, became extinct. The late Ludfordian graptolite recovery gave origin to a novel fauna of Pridoli type from taxa that emerged or just reappeared above the Kozlowskii crisis. In Všeradice and elsewhere in the Prague Synform, the recovery, manifested by the appearance of Pseudomonoclimacis latilobus and Slovinograptus balticus, closely postdates the end of the isotope excursion but pre-dates the first appearance of the conodont index 'Ozarkodina' snajdri. Here the graptolite recovery was delayed relative to the recovery of the benthic fauna. A canalized intraformational limestone conglomerate corresponds with a gap in the sedimentary record above the Kozlowskii extinction and just below the graptolite recovery. The benthic faunas from the conglomerate matrix and pebbles permit correlation with the shallower part of the basin indicating a distinct fall in sea-level. The present data demonstrate the coincidence of the graptolite crisis with benthic faunal change and eustatic fall in sea-level manifested by facies change and the carbon isotope excursion. Polonograptus chlupaci sp. nov., from the Nc. kozlowskii Biozone, is described and several other graptolite taxa are redescribed.

A jawed polychaete fauna from the late Ludlow Kozlowskii event interval in the Prague Basin (Czech Republic)

“…This is not surprising considering that the event is associated with the largest positive carbon isotope excursion of the Phanerozoic (Lehnert et al 2003, Munnecke et al 2003, dramatic faunal turnovers (see summary in Jeppsson & Aldridge 2000, Calner 2008) and a collapse of the marine ecosystem (Calner 2005). Profound biotic changes have been recorded, e.g., among conodonts (Jeppsson & Aldridge 2000), acritarchs (Stricanne et al 2006), graptolites (Urbanek 1993, Štorch 1995, Melchin et al 1998, Manda et al 2012, cephalopods (Manda 2008) and fish ). Barrick et al (2010, p. 32), on the other hand, recorded "normal ecological adjustments to environmental changes" rather than major extinctions and ecosystem collapse, although, as noted by those authors, based on limited faunal data.…”

“…This succession has recently been investigated for graptolite biostratigraphy (Štorch 1995) and the Kozlowskii event (Manda & Kříž 2006, Lehnert et al 2007, Manda et al 2012.…”

“…The Ludfordian (late Silurian) environmental and biological crisis known as Lau and/or Kozlowskii event (for Lau and Kozlowskii event correlation problems, see Manda et al 2012 and references therein) has received increasing attention since the introduction of the Lau event by Jeppsson (1993) and Kozlowskii event by Urbanek (1993). This is not surprising considering that the event is associated with the largest positive carbon isotope excursion of the Phanerozoic (Lehnert et al 2003, Munnecke et al 2003, dramatic faunal turnovers (see summary in Jeppsson & Aldridge 2000, Calner 2008) and a collapse of the marine ecosystem (Calner 2005).…”

"An endocochleate experiment" in the Silurian straight-shelled cephalopod Sphooceras

“…This level corresponds with the onset of the Kozlowskii and Lau extinction event (Urbanek 1993, Calner 2008, Manda et al 2012. Three paleopopulations were examined, from three thin beds with erosive surfaces, each representing a single depositional event: Zadní KopaninaNad Jirasovým lomem, bed No.…”

Facies development and sequence stratigraphy of the Ludfordian (Upper Silurian) deposits in the Zbruch River Valley, Podolia, western Ukraine: local facies overprint on the δ13Ccarb record of a global stable carbon isotope excursion

“…Of potential utility for constraining the stratigraphic position of the interval investigated in the present study is the positive stable CIE recognized globally in the Ludfordian (Wenzel and Joachimski 1996;Bickert et al 1997;Kaljo et al 1997;Azmy et al 1998;Wigforss-Lange 1999;Wenzel et al 2000;Saltzman 2001;Calner 2005b;Martma et al 2005;Kaljo and Martma 2006;Jeppsson et al 2007;Kaljo et al 2007;Lehnert et al 2007;Eriksson and Calner 2008;Barrick et al 2010;Kozłowski and Munnecke 2010;Munnecke et al 2010;Cramer et al 2011;Loydell and Frýda 2011;Kaljo et al 2012;Kozłowski and Sobień 2012;Manda et al 2012). The beginning of the excursion coincides with an abrupt decrease in abundance of Polygnathoides siluricus, shortly before its Last Appearance Datum (LAD) (Martma et al 2005;Kaljo and Martma 2006;Jeppsson et al 2007;Lehnert et al 2007;Eriksson and Calner 2008).…”