Henriet, J. P., Hamoumi, N., Da Silva, A. C., Foubert, A., Lauridsen, B. W., Rüggeberg, Andres and Van Rooij, D. (2014) Carbonate mounds: From paradox to World Heritage. Marine Geology, 352 . pp. 89-110. DOI 10.1016/j.margeo.2014.01.008.

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Abstract

The recent marine carbonate world comprises two major compartments: (1) the surface domain of the
photozoan carbonates, confined in space by water depth and by the penetration of light, and (2) a deep domain,
where heterozoan mound-builder guilds directly forage on fluxes of nutrients, which primarily percolate from
the photic zone and/or are generated by in situ benthic processes. Locally, giant cold-water coral mounds
tower up to heights of 150 to 250 m above the sea floor, in general between 500 and 1300 m water depth and
within sharply delineated provinces. Some 15 years of research on these giant mound provinces conveys a picture
of their distribution in space and possibly sheds light on controls, acting in concert. Globally, there is no counterpart
for the prolific North Atlantic Mound Basin (NAMB). A chemical control is seen by an overlay of the
mound provinces on a map of the aragonite saturation horizon (ASH). An external physical control is inferred
fromthe position of themound provinces, girdling a vigorous North Atlantic subtropical gyre systemand clustering
close to the roof of the intermediate to deep water masses of a dynamically stratified ocean. On the eastern
boundary of the NAMB, nutrient fluxes are enhanced by mixing processes, driven either by internal waves between
Galicia and the Shetlands, or by the vast and heterogeneous Eastern Boundary Upwelling System along
the Iberian/African margins down to 10°N. Early diagenesis by carbonate dissolution and re-precipitation driven
by convecting or advecting internal fluids can contribute to stabilize such constructions, facilitating an exuberant
vertical accretion. It is speculated that in theNorth Atlantic Ocean, the deep-water carbonate factory outclasses in
size the shallow water coral reefs.
Giant mound formation is a recurrent play of Life since the dawn of the metazoans (Nama Group, Upper
Neoproterozoic), however with actors and plots, varying from act to act. Remarkably, literature reports only
three occurrences of deep-water mounds in the Phanerozoic: the modern ocean, possibly the Danian, and the
Carboniferous. Some striking parallelisms in the development of the Atlantic and the Paleo-Tethys oceans, combined
with the developing insights in the controls on deep-watermounds in the present ocean, invite for a comparative
study. This has the potential to eventually shed light on the full circulation pattern of the Paleo-Tethys
Ocean, surface and deep. Comparative studies will build upon (1) modeling of ocean circulation constrained by
the record of deep-water carbonate systems and supported by advances in tracer and proxy tools, and (2) field
studies on representative and accessible continental locations. The mound route that develops in Morocco
under the auspices of IOC-UNESCO will provide tomulti-disciplinary teams with marine and continental experience
opportunities for confronting observations from the modern ocean and on key records of past oceanic basins.
It has the potential to eventually qualify for a UNESCO recognition as World Heritage.

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