Lower Palaeozoic rocks in the Karadere-Zirze area, east of Safranbolu (Pontides, northern
Turkey), range from Early Ordovician to Silurian. Overlying the probably Tremadoc Bakacak
Formation are Aydos Formation quartzites, followed conformably by the Karadere Formation, dated
as Early Arenig to Early Llanvirn by means of graptolites which are assigned to seventeen genera
and include three new forms: Eoglyptograptus bouceki, Prolasiograptus haplus praecursor and
Undulograptus? mui. Late Arenig trilobites from the Karadere Formation include Bergamia,
Cyclopyge, Dionidella?, Leioshumardia and Seleneceme. In the Limestone Member of the overlying
Ketencikdere Formation, uncommon trilobites suggest only a mid- to late Ordovician age, but conodonts
with Colour Alteration Index 5–6 indicate the Amorphognathus tvaerensis Biozone (early
Caradoc). Macrofossils are rare in the Siltstone Member, but conodonts from the middle of the unit
suggest the highest subzone of the A. tvaerensis Biozone; the youngest visible strata are, on acritarch
evidence, at least as high as Caradoc, but the Ashgill is not confirmed and the contact with overlying
Silurian rocks is unexposed. The Findikli Formation comprises: a Lower Member, black argillites with
Llandovery graptolites and acritarchs; and an Upper Member, grey shales with late Wenlock graptolites,
overlain unconformably by Devonian rocks. The succession differs significantly from contemporaneous
deposits in southern Turkey and its affinities lie with western Europe, including the Welsh
Basin.