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Współczesne głębokomorskie budowle węglanowe - nieznany świat podmorskich oaz

Jakubowicz M.

Przegląd Geologiczny

2012

Vol. 60, nr 6

325-332

Deep-marine carbonate buildups constitute one of the most spectacular and enigmatic features found on modern seafloors. Despite some characteristics shared by all the deep-marine carbonate buildups, they represent, in fact, several distinct types, which differ in terms of their geneses, as well as sedimentary, biotic and geochemical features. These structures can be roughly divided into hydrocarbon seep limestones, carbonate-built hydrothermal vents and deep-water coral reefs. The former group include carbonate concretions, lenses, mud mounds and mud volcanoes forming as a result of decrease in alkalinity, caused by an activity of methane-oxidizing microbes. The rare examples of hydrothermal-derived limestone columns, in turn, grow in response to mixing of ambient, cold seawater and warm, Ca2+-rich fluids originating from peridotite massifs. In contrast, growth of the deep-water coral reefs appears to be stimulated largely by hydrological and bathymetric constraints, whereas a potential input of fluid seepage is rather of subordinate importance in diagenetic lithification of these structures. Surprisingly, studies on deep-water carbonates may turn out to be relevant also for understanding the shallow-water carbonate factories, providing evidence, that abiotic factors are more important in marine limestone precipitation than previously thought.

Discovery of thermophilic corals in an ancient hydrothermal vent community, Devonian, Morocco

Bełka Z., Berkowski B.

Acta Geologica Polonica

2005

Vol. 55, no. 1

1-7

Living corals are remarkably broad in their thermal and bathymetric ranges. But corals that could tolerate abnormally high temperatures (higher than 40 C) are unknown both in the living communities and in the fossil record. Here we report the discovery of small thermophilic rugose corals in the Devonian vent community of southeastern Morocco. These organisms were adapted to conditions prevailing within chimney conduits of a hydrothermal system that developed on the roof of a submarine volcanic high. The coral larvae followed a calice-in-calice settlement and growth strategy to survive the contact with thermal fluids. This adaptation was not related to taxonomy and characteristic of all coral taxa present in the vents. Monospecific coral population was identified in several Emsian vents whereas the coral fauna of the single Givetian vent was more diverse and included four species.The entry of different rugose coral species into the hot vents resulted from a trophic relation to ostracods flourishing in the chimneys.