Growth and submarine fossilization of algal cup reefs, Bermuda*

• Published in: Sedimentology
• Main Authors: GINSBURG, R. N., SCHROEDER, JOHANNES H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1973
• Subjects: Planktonic foraminifera
• Online Access: http://dx.doi.org/10.1111/j.1365-3091.1973.tb01633.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-3091.1973.tb01633.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3091.1973.tb01633.x

ABSTRACT Small charges of explosives were used to section cup‐shaped reefs that occur on the margins of the Bermuda Platform. Study of these artificial outcrops, up to 10 m high, and the samples collected from them show how the reef‐building community is rapidly converted to well‐lithified reef rock in the marine development. The reefs, known locally as boilers and breakers, occur along the wave‐swept south shore of the Bermuda Islands and around the northeast and northwest margins of the Platform. They are cup‐shaped, up to 30 m in long dimensions, and rise up to the sea surface as much as 12 m above the surrounding sea floor. The reefs are built by an intergrowth of encrusting organisms, principally crustose coralline algae, an encrusting hydrozoan, Millepora sp., and an attached gastropod, Dendropoma irregulare. The growth framework of these algal cup reefs has extensive voids: large and intermediate‐sized growth framework and shelter pores; borings of bivalves and sponges; and both intra‐ and inter‐particle pores. A variety of vagile and sessile organisms (coelobites) inhabit these pores: an encrusting Foraminifera, Homotrema rubrum , is the most abundant attached coelobite; the tests of a variety of benthic Foraminifera and ostracods are common: branched coralline algae, barnacles, bivalves, ahermatypic corals, bryozoans, and burrowing crustaceans occur in varying abundance. Beginning millimetres below the living surface, internal sediments accumulate in the extensive voids. Coarse‐grained skeletal sand derived from the surface of the reefs is characteristic of the larger voids; lime mud with the tests of planktonic Foraminifera and planktonic algae occurs generally in the smaller voids. Most specimens from the interior of the reefs show multiple generations of internal sediment that vary in grain size, composition, and colour. The sand‐sized sediments are pumped into the voids by the frequent and intense wave action; the lime mud settles out in the smaller, less agitated pores. Cementation of internal ...