Late Viséan/early Serpukhovian conodont succession from the Triollo section, Palencia (Cantabrian Mountains, Spain)

The present study reports upon the conodont faunas of the uppermost lower Viséan (Carrión unit) through the lower Serpukhovian (Peña unit) deep water Triollo section, Cantabrian Mountains, Palencia, Spain. The condensed succession of grey, laminate, nodular and cherty limestones with marl intercalations contains abundant and diverse conodont faunas. Three new species of Vogelgnathus, V. cantabricus, V. palentinus and V. triolloensis, as well as one new species and one new subspecies of Gnathodus, Gn. boogaardi and Gnathodus girtyi pyrenaeus Nemyrovska & Perret subsp. nov., are described. All stratigraphically important taxa for the studied interval are described. Four conodont zones are distinguished, three in the Viséan, Gnathodus praebilineatus, Gn. bilineatus and Lochriea nodosa Zones, and one in the lower Serpukhovian, L. ziegleri Zone. It is proposed to identify the Viséan/Serpukhovian boundary at the first appearance of L. ziegleri. The Triollo carbonate succession (Carrión and Peña units) is compared by conodonts with coeval deposits in other areas. The conodonts are divided into eight palaeoecological groups, their occurrences are analysed and diagrammatically illustrated. Four peaks representing invasions of the Vogelgnathus-dominated faunas may correspond to the four flooding events during late Viséan and early Serpukhovian times. Investigations of the conodont biofacies together with sedimentological studies of the Triollo sections indicate deep water, basinal depositional conditions.