Stromatoporoids from the latest reefal episode in the Devonian (late Frasnian) of the Cantabrian Mountains (NW Spain)

摘要

In the Palaeozoic series of the Cantabrian Mountains, reefal carbonates occur first in the Devonian of the Asturian-Leonese Domain. In this period seven reefal episodes of different importance, starting from the Early Devonian to the Late Devonian were developed. The latest of these Devonian reefal episodes is very local and took place in the late Frasnian during deposition of the Cremenes Limestone. About 80 stromatoporoid samples were collected from three sections located on the southern slope of the Cantabrian Mountains, where only a few species occur. The specimens here described are assigned to Stictostroma saginatum, Stictostroma? sp., Clathrocoilona spissa, Clathrocoilona cf. inconstans, Clathrocoilona sp. and Stachyodes australe. None of these species had previously been reported from the Cantabrian Mountains. Most stromatoporoids show laminar growth forms, in some cases with well-developed mamelons. This type of morphology is possibly a response to palaeoenvironmental conditions. Numerous associations with other organisms such as bryozoans (fistuliporids), algae (Sphaerocodium sp.), laminar tabulates (alveolitids) and worms (Spirorbis sp.) are present. Finally, the stromatoporoids of the Cremenes Limestone are compared with other stromatoporoid faunas from reefal levels of similar age from the Boulonnais (northern France), Namur and Dinant Synclinoria in the Ardennes (Belgiun), and Kerman and Esfahan areas (Iran) showing four common species (S. saginatum, C. spissa, C. inconstans and S. australe).