MoccAMeBo - Climate-driven initiation and development of cold-water coral mounds along the Moroccan Atlantic margin revealed by MeBo-cores
Final Report Abstract
Within the frame of the DFG-project MoccAMeBo, cold-water coral mounds occurring as exposed and buried structures within an extended province along the Atlantic Moroccan margin (AMCP) were studied with a focus (i) on the temporal variability of mound formation in relation to environmental forcing since the Late Pleistocene, and (ii) on their spatial distribution and areal dimension. These are the highlights of the project results: Cold-water coral mound formation in the AMCP shows a discontinuous pattern and occurs predominantly during glacial periods (at least going back to MIS10). The base of one coral mound (Wulle Mound) of the AMCP was penetrated during MeBo drilling and is dated back to ~340-350 ka BP. This record is unique as it represents one of the very few examples of Atlantic coral mounds for which the timing of initiation could be determined. Moreover, the new record reveals that considering the different known Atlantic mound provinces the timing of mound initiation as well as mound formation pattern are far more variable than previously assumed. Mound formation in the AMCP was most pronounced during the Last Glacial Maximum reaching high aggradation rates of >90 cm/kyr. Beside enhanced productivity conditions, which is assumed to have triggered mound formation in the AMCP during the last glacial, the outcome of the MoccAMeBo project provides first hints that a vigorous bottom current regime is an additional crucial environmental control. While mound formation in the AMCP was more or less restricted to glacial periods, a MeBo drill record obtained from an off-mound site contemporaneously revealed a low sedimentation rate or even a lack of sediments. This observation provides some evidence for the assumption that enhanced mound formation preliminary occurs under highly dynamic bottom current conditions, which at the same time often prevent sediment deposition (erosion, non-deposition) in the surrounding area. More than 3,400 exposed coral mounds were mapped in the AMCP (mound density: 2.4 mounds/km2), which show a conspicuous arrangement into two slope-parallel belts. With ~25% of all mounds occurring deeper than 900 m, the coral mounds of the AMCP are among the deepest coral mounds described so far. The majority of exposed coral mounds of the AMCP have an elongated shape and are mostly extended downslope rather than parallel to the continental slope. The shape and orientation of the mounds point to a significant influence of internal waves in the mound formation process. Several generations of buried coral mounds exist in the AMCP, which root on at least ten different horizons that are tentatively related to glacial periods since the Early-Middle Pleistocene Transition. Moreover, while some mounds became completely buried at a certain point of time, others were able to re-start mound formation once optimal environmental conditions for the proliferation of corals re-established. Buried mounds are ~3.7 times more frequent than the exposed mounds. Consequently, a remarkably high total number of ~16,000 buried and exposed mounds is estimated for the mapped area (1,440 km2) of the AMCP. All new findings obtained during the DFG-project MoccAMeBo underline Morocco’s role as a "hotspot" area for the occurrence of cold-water coral mounds within the Atlantic Ocean.
Publications
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(2015). MoccoMeBo, Climate-driven development of Moroccan cold-water coral mounds revealed by MeBo-drilling: Atlantic vs. Mediterranean settings. Cruise MSM36 – February 18-March 17, 2014 – Malaga-Las Palmas. MARIA S. MERIAN-Berichte, 47 pp, DFG-Senatskommission für Ozeanographie, ISSN 2195-8483
Hebbeln D, Wienberg C, and MSM36 cruise participants
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(2016). Good neighbours shaped by vigorous currents: coldwater coral mounds and contourites in the North Atlantic. Marine Geology 378: 171–185
Hebbeln D, Van Rooij D, Wienberg C
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(2017). Multiple generations of buried cold-water coral mounds since the Early-Middle Pleistocene Transition in the Atlantic Moroccan Coral Province, southern Gulf of Cádiz. Palaeogeography, Palaeoclimatology, Palaeoecology 485: 293-304
Vandorpe T, Wienberg C, Hebbeln D, Van den Berghe M, Gaide S, Wintersteller P, Van Rooij D
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(2019): 8 Highly Variable Submarine Landscapes in the Alborán Sea Created by Cold-Water Corals. In: Covadonga Orejas und Carlos Jiménez (Hg.): Mediterranean Cold-Water Corals: Past, Present and Future, Bd. 9. Cham: Springer International Publishing (Cora
Hebbeln D
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A Deglacial Cold-Water Coral Boom in the Alborán Sea: From Coral Mounds and Species Dominance. In: Orejas C., Jiménez C. (eds) Mediterranean Cold-Water Corals: Past, Present and Future. Coral Reefs of the World, vol 9. Springer, Cham S. 57-60
Wienberg C
