Emsian Stage

Emsian Stage

 

the upper stage of the Lower Devonian system (period). At its type location, the Emsian is represented by a thick layer of sandstones, clays, and shales. Two substages have been identified in the Ardennes-Rhine region. The upper substage is characterized by a change in the marine fauna and the appearance of Middle Devonian groups, such as brachiopods, trilo-bites (Basidechenella), goniatites (Anarcestes), and corals (Calceolo sandalina).

The Emsian Stage corresponds to the upper part of the Co-blenzian Stage in Belgium. In the USSR it corresponds approximately to the upper part of the Lower Devonian and the lower part of the Eifelian Stage. [SeeDEVONIAN SYSTEM (PERIOD).]

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(2008): Comments on the GSSP for the basal Emsian stage boundary: the need for its redefinition.
The Emsian Stage appears to be much longer than earlier considered, and the Eifelian and Givetian are significantly shorter (Kaufmann 2006, fig.
The results of the U-Pb zircon geochronology (G1 = 394.4 [+ or -] 2.2 Ma; G2~402 Ma; G3 39Z7 [+ or -] 1.1 Ma; G4 = 399.5 [+ or -] 0.8 Ma) indicate that the emplacement of the early suite occurred over at least 8 Ma and belongs to the Late Emsian stage. Samples of commingled diorite (G3) and granite (G4) yield ages that are indistinguishable within error.
2 and Table 2) indicate that the emplacement of the early suite occurred over at least 8 Ma and belongs to the late Emsian stage (Megacrystic Granite G1--394.4 [+ or -] 2.2 Ma; Megacrystic Granite G2-402 Ma; Diorite Enclave G3--39Z7 [+ or -] 1.1 Ma; MMZ Granodiorite G4 = 399.5 [+ or -] 0.8 Ma).
According to this, the boundaries and biozones of the Emsian Stage are based essentially upon the successive occurrence of, phylogenetically related, species of the genus Polygnathus (see for example Klapper and Johnson, 1975; Klapper, 1977; Weddige and Ziegler, 1977; Lane and Ormiston, 1979; Yolkin et al., 1994; Bardashev et al., 2002).