Post-Lau Event (late Ludfordian, Silurian) recovery of conodont faunas of Bohemia

 

Authors: Slavík L, Carls P

Published in: Bulletin of Geosciences, volume 87, issue 4; pages: 815 - 832; Received 30 May 2012; Accepted in revised form 20 August 2012; Online 15 October 2012

Keywords: late Silurian, Ludfordian, post-Lau Event, conodont recovery, Lau Event, Prague Synform,

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Abstract

The effects of the Lau Event on conodont faunas in shallow water environments of the Prague Synform were rather moderate in comparison with Gotland. The post-event restoration of conodont diversity following the characteristic post-siluricus faunas with diminished elements and dominated by a long-ranging stock of Delotaxis was gradual and not abrupt. This points to absence of such large gaps in the sedimentation like they had occurred below and had caused the lack of a large upper part of the siluricus Zone. Accordingly, the Bohemian conodont record of diversifying conodont faunas, starting with the entry of “slender spathognathodontids”, is comparably complete. Increased diversity and abundance of incoming conodont taxa has enabled a refinement of the regional zonal subdivision. This includes the succession of the plodowskii, latialatus, parasnajdri and crispa conodont biozones for the interval following the Lau Event in the late Ludfordian. The conodont data from Bohemia show that “Oz.snajdri range is largely included in the overlap of Pedavis latialatus and “Ozarkodinacrispa. Accordingly, the use of the problematic stratigraphical unit - the snajdri Interval Zone as a base for the definition of a middle Ludfordian Stage Slice can be misleading. Conspicuous morphological changes in the “Ozarkodinasnadri-Oz.crispa stocks and in the Ozarkodina typica lineage allow refined inter-regional correlations.