4 páginas, 5 figuras.-- Trabajo presentadpo en la 40ª Sesión Científica, León, 2006.Preliminary studies of some stratigraphic sections spanning the Ordovician-Silurian boundary in the southern Cantabrian
Zone (Iberian Massif, NW Spain) demonstrate the existence of a record of Hirnantian glaciomarine diamictites and
shallow-water quartzites in at least three localities, situated in the Bodón nappe. These rocks, evidenced for the first time
in the Cantabrian Zone, are probably related to the infilling of a paleorelief, scoured in the Barrios Formation during the
Late Ordovician glaciation. The occurrence of an ubiquitous quartzite unit, generally related to the Ordovician-Silurian
boundary in most parts of northern Gondwana, is now extended to the outcrops here analyzed. The Hirnantian
quarzite probably occurs in additional areas of the Bodón and Correcilla nappes, where its location and significance
might be underestimated, and described as the uppermost part of the Barrios Formation (Middle Cambrian to Arenigian).
The same quartzite is probably recognized in the areas with volcanic necks within the Barrios Formation, and also in its
stratotype, in which a latest Ordovician/earliest Silurian quartzite overlies unconformably on Middle Ordovician shales.Esta
nota es una contribución al proyecto 503
del Programa Internacional de Geociencias
(IUGS-UNESCO) y se inscribe en las actividades
del Grupo de Precámbrico y Paleozoico
perigondwánico de la Universidad
Complutense de Madrid.Peer reviewe
