Distribution and faunal composition of temperate heterozoan carbonates of the shelf off Asturias(North Spain) and Norway.

Vina Herbon, Cristina (1998) Distribution and faunal composition of temperate heterozoan carbonates of the shelf off Asturias(North Spain) and Norway. University of Southampton, Doctoral Thesis.

Abstract

Coarse carbonate sand from between 15 to 50 m water depth from the Asturias (North Spain) and Norwegian shelves were studied. They belong to the Heterozoan association. The high amount of gastropods allows the creation of three new skeletal assemblages gastromol, bigastromol and barngastromol. Multidimensional scaling (MDS) analysis using the PRIMER programme is used to study the assemblages of the species. The Asturias shelf is an area rich in mollusc species which contribute their shells to the formation of carbonate sediments. These species are used to recognise the movement of sediment on this shelf. The dominant species are Bittium reticulatum and Arca tetragona. A large amount of mollusc species found on this shelf come from rocky sea floor areas from the subtidal zone with a dense algal population and sea-grasses. Other species identified are typical of a marine inner shelf with energetic conditions and benthic currents. On the shelf the lack of specimens from supra-intertidal species that usually accumulate on beaches suggests that there is not a benthic current that moves sediments from the coast onto the shelf.

On the Norwegian shelf there is a more taxonomic variety in the dominant groups and there are seven skeletal assemblages. The dominant groups are molluscs, polychaetes, cirripeds and foraminiferans. Some of the mollusc species found indicate an origin in shallow water areas with sea-grass populations and presence of low salinity water and also shallow rocky areas. On the other hand, other species are typical of an inner shelf.

Analyses of shell surfaces were also undertaken showing four types of texture: unaltered, corroded, polished, and stained. These last three types are an alteration of the colour and ornament of the shells. Another important feature of the mollusc shells from both shelves is the high amount of microboring.

In conclusion, it can be said that in spite of the wide geographic separation, the carbonate sediments of the Asturias and Norwegian shelves show remarkable faunal similarity.

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