Blieck, Alain R. M.Karatajūtē-Talimaa, Valentina N.Mark-Kurik, Elga2002FIG. 5 in Upper Silurian and Devonian heterostracan pteraspidomorphs (Vertebrata) from Severnaya Zemlya (Russia): a preliminary report with biogeographical and biostratigraphical implications10.5281/zenodo.4665035FIG. 5. — Biostratigraphical correlations for some of the Circum-Arctic, Upper Silurian-Lower Devonian heterostracan-bearing sequences, after Blieck et al. (1987: fig. 9, modified).FormationDelorme)Upper(.FmWhittakerN.WCANADAMackenzie.T.?BaySnowblind?FormationCANADIANIslandSomersetARCHIPELAGONunavut?FormationSoundPeelFormationARCTICFormationSoundPeel??MemberUpperMemberLower?GroupBayRedBayWoodSVALBARDSpitsbergenFormation.FmNevisBen.FmFraenkelryggen?OctoberUst’Formationemnaya’Pod’-RusanovSpokojnayaZEMLYAIslandSEVERNAYASevernayaBukhtaZemlyaFormationKrasnayaFormationFormationSpokojnayaRevolutionFmLowerFmUpper+Middle..˘EmsianPragianPridoliLudlowLochkovian