MoccAMeBo - Climate-driven initiation and development of cold-water coral mounds along the Moroccan Atlantic margin revealed by MeBo-cores

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Scleractinian cold-water corals (CWC) are capable of forming substantial 3-dimensional seafloor structures, so-called coral mounds. These mounds are composed of CWC fragments and hemipelagic sediments, which deposited over thousands to millions of years. Along the Moroccan Atlantic margin, hundreds of small-sized coral mounds exist in water depths between 500 and 1000 m, which rarely reach elevations higher than 10-20 m above the seafloor. Today, living CWC are almost completely absent in this Moroccan Atlantic Coral Province (MACP) while fossil coral accumulations are widespread. Moreover, it has been shown that along the Moroccan Atlantic margin CWC growth (and thus mound accretion) was most pronounced during the last glacial, presumably triggered by enhanced productivity, and terminated with the onset of the Holocene. However, these findings just refer to the upper 6 meters of the coral mounds, as up to date no longer material was available. During expedition MSM36 with RV MARIA S. MERIAN in spring 2014, records with remarkable long recoveries of several tens of meters were collected along the Moroccan Atlantic margin with the MARUM sea floor drill rig MeBo. Thereby, two coral mounds of the MACP could be completely penetrated down to their bases. The two obtained "on-mound" MeBo records (reaching max. drilling depths of ~47-52 m) will allow to gain some substantial and detailed insight into the initiation and early development of the Moroccan coral mounds, which is essentially unknown so far. In addition, an "off-mound" MeBo record (comprising two parallel drillings) was retrieved from an area in between the Moroccan coral mounds reaching maximum drilling depths of 45 m. This record will provide unique palaeoceanographic information about climate-driven environmental changes covering several glacial-interglacial cycles, and thus, will allow to test if the link between surface water productivity and CWC growth as identified for the last glacial is a long-lasting feature in the MACP. Moreover, the off-mound record was placed in an area marked by numerous buried mounds which comprise different generations of coral mounds rooted on different reflectors, thus allowing for an assessment of the nature of those reflectors forming either the base of the mounds or the first coverage once the mounds stopped growing. Overall, the four MeBo cores selected for the proposed project offer high-quality records, which will significantly improve our understanding of the ultimate climatic link driving the forcing factors that control the occurrence and development of CWC in the MACP. In particular with the now available complete mound records some fundamental topics in CWC and coral mound research can be addressed.