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Monterey Bay Studies

Monterey Bay Studies


Monterey Bay National Marine Sanctuary Project, 1999

Recent Benthic Foraminiferal Biofacies of the Monterey Bay Shelf and Canyon Slopes

by Mary McGann


The bottom biota of the Monterey Bay region includes an extremely diverse microfauna. Benthic foraminifers collected from a series of box and multi-cores from nearshore to bathyal depths in the Monterey and Soquel Canyons can be separated into three distinct biofacies. The shallowest biofacies, occurring from 0-50 m water depth, is comprised of calcareous perforate foraminifers dominated by Cassidulina limbata with abundant Elphidiella hannai, Cibicides lobatulus, Buccella frigida, Rotorbinella rosacea, Elphidium excavatum selseyensis and E. excavatum clavatum. An intermediate biofacies, comprised nearly exclusively of arenaceous foraminiferal species, is present from 50 m to the shelfbreak (~120 m): Goesella flintii dominates the fauna at 50 m, Ammotium planissimus at 70-90 m, and Reophax scorpiurus, Alveolophragmium advena, A. columbiense, and Gaudryina arenaria at 100- 120 m. Within this zone of concentrated arenaceous foraminifers on the outer shelf lies an anomalous deposit of highly biogenic sediment west of Fort Ord (50-80 m) which looks remarkably similar to sediments collected from Cordell Bank to the north and includes the calcareous perforate foraminiferal taxa Cassidulina tortuosa, C. californica, Cibicides lobatulus, Trifarina baggi, T. angulosa, Rotorbinella rosacea and Planulina exorna. The deepest biofacies occurs between 1100 and 1400 m on the slopes of Monterey and Soquel Canyons and contains a calcareous perforate fauna which is dominated by low-oxygen species Epistominella pacifica, Buliminella tenuata, Bolivina argentea, Globobulimina affinis, and Chilostomella ovoidea, reflecting the presence of dysaerobic waters.

This abstract is from Monterey Bay National Marine Sanctuary Symposium, Sanctuary Currents '96, Building Community Connections in Science, Education and Conservation, Poster Session, 1996.

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