Running across the Silurian/Devonian Boundary along Northern Gondwana: A Conodont Perspective

Abstract

The Global Stratotype Section and Point (GSSP) of the Silurian/Devonian boundary, Lower Devonian Series and Lochkovian Stage was formally placed in 1977 at Klonk, in the Czech Republic, at the first appearance of the graptolite Uncinatograptus uniformis uniformis (Přibyl). However, since then, correlation of this limit has been often hampered in carbonate facies where graptolites are uncommon or totally absent. A large calcareous deposition occurred at the Silurian/Devonian boundary along the northern and peri-Gondwana margin, thus representing an ideal location to select and test a possible additional biostratigraphic marker of the limit among conodonts. The first appearance of Caudicriodus hesperius almost simultaneously at the base of the Devonian in Bohemia, the Carnic Alps, Sardinia, Morocco and elsewhere indicates that this taxon is the conodont that best approximates the beginning of the Period. The first or last appearance of other species (e.g., Ozarkodina confluens, Zieglerodina klonkensis, Z. remscheidensis and Caudicriodus woschmidti) may help to recognise the boundary as well.

The latest encrinurid trilobites from the Lower Devonian of Xinjiang, Northwest China

“…According to Jeppsson (1988), Caudicriodus (specifically Caudicriodus woschmidti ) occurs slightly before Monograptus uniformis uniformis in some sections, but this fact may be due to facies control (Corradini & Corriga, 2012). The appearance of Caudicriodus (or Icriodus ) is still believed to coincide with the beginning of the Devonian period (Corradini & Corriga, 2012; Slavik & Hladil, 2020; Ferretti et al 2022). Caudicriodus angustoides bidentatus (Fig.…”