Ordovician sponges (Porifera) and other silicifications from Baltica in Neogene and Pleistocene fluvial deposits of the Netherlands and northern Germany

Abstract

Fluvial deposits of Miocene to Early Pleistocene age in Germany and the Netherlands were laid down in the delta of the Eridanos River System, but the exact provenance of this material continues to be a subject of discussion. The aim of the present study is twofold. Firstly, a comparison of Ordovician sponges in these deposits with those from northern Estonia and the St Petersburg region (Russia) demonstrates that these erratics originated from the drainage area of the Pra Neva, a tributary of the Eridanos. Secondly, the importance of Late Ordovician silicified boulders, which yield forms of preservation that are unknown in comparable fossils, preserved in situ, is outlined. Some recommendations for future studies are made.

Importance of Dimorphosiphon (Chlorophyta, Bryopsidales) for Facies and Paleobiogeographic Studies of the Upper Ordovician Richmondian Red River Formation, Williston Basin

“…Fluvial Erratics of the Miocene-early Pleistocene Eridanos River System, The Netherlands and Northern Germany (Western Margin of Baltica).-Dimorphosiphon rectangulare has recently been identified from fluvially transported limestone boulders in northern Germany and The Netherlands (Rhebergen, 2009). The boulders were laid down in the Miocene to early Pleistocene Eridanos River delta, the provenance being a large drainage area surrounding the present-day Baltic Sea.…”

Late Ordovician rostroconchs (Mollusca) from fluvial erratics in northwestern Europe

“…The river system was destroyed by the middle and late Pleistocene glaciers. Rhebergen (2009) and Van Keulen et al (2012) distinguished between several types of Ordovician fluvial erratics deposited by the Eridanos in the Dutch-German border area. All erratics are secondarily silicified limestone which derive from different regions and have different transport histories and ages although their faunal assemblages suggest a provenance of the North Estonian Confacies Belt (Tab.…”

“…All erratics are secondarily silicified limestone which derive from different regions and have different transport histories and ages although their faunal assemblages suggest a provenance of the North Estonian Confacies Belt (Tab. 1; see discussion in Rhebergen 2009). …”

“…More abundant is a varied Pirgu group of erratics (Rhebergen 2009). One type is called the brown Pirgu chert/limestone (Brauner Pirgu-Hornstein) which stands out by its dark brown colours and fossils preserved with a porcelain type quality.…”

“…The material described herein will therefore be referred to as Haljala group erratics or Haljala erratics following Rhebergen (2009).…”