A 300 000-year record of cold-water coral mound build-up at the East Melilla Coral Province (SE Alboran Sea, western Mediterranean)

Abstract

Abstract. This study provides a detailed reconstruction of cold-water coral mound build-up within the East Melilla Coral Province (southeastern Alboran Sea), more precisely at the northern part of Brittlestar Ridge I, over the last 300 kyr. The multiproxy investigation of core MD13-3462G reveals that mound build-up took place during both interglacial and glacial periods at average aggradation rates ranging between 1 and 10 cm kyr−1. These observations imply that corals never thrived but rather developed under stressful environmental conditions. Maximum aggradation rates of 18 cm kyr−1 are recorded during the last glacial period, hence providing the first evidence of coral mound development during this time period in the western Mediterranean. The planktonic (Globigerina bulloides) and benthic (Lobatula lobatula) δ18O records from core MD13-3462G show typical interglacial–glacial variations during the last two interglacial–glacial cycles. This is in contrast with δ18O records generally recovered from coral mounds and highlights that the northern part of Brittlestar Ridge I experienced reduced albeit relatively continuous accretion. High abundances of infaunal benthic foraminifera (Bulimina marginata, Bulimina striata, and Uvigerina mediterranea) suggest that weak seafloor oxygenation associated with important terrestrial organic matter input characterized interglacial periods, whilst the dominance of large epibenthic species (Discanomalina coronata and Lobatula lobatula) and Miliolids is probably linked to stronger Levantine Intermediate Water circulation and fresher organic matter input during glacial periods. In addition, the computed tomography (CT) quantification of macrofaunal remains shows that the bryozoan Buskea dichotoma is present throughout the entire 300 kyr of mound build-up history, with the exception of MIS 5, and is possibly a key contributor to mound development during glacial periods. The comparison of our observations to other long-term coral mound records demonstrates that western and central Mediterranean coral mounds do not show concurrent build-up over interglacial–glacial cycles, implying that their development may be driven by regional and local environmental forcing.

Decline in cold-water coral growth promotes molluscan diversity: A paleontological perspective from a cold-water coral mound in the western Mediterranean Sea

“…* see Section 3.1 for explanation. Fentimen et al, 2022). Consequently, these minor age reversals only lead to small uncertainties in the age model.…”

“…In all cores, a few non-chronological U/Th ages had to be excluded from age-to-age calculations (Table 1) as it is the case for many other coral mound deposits (e.g., Matos et al, 2017;Fentimen et al, 2022;Wienberg et al, 2022). In core GeoB13728-2, ages from core depths of 62, 217, and 354 cm were excluded because these ages exhibit a distinct offset to the general age trend of all other U/Th ages that is independently supported by several AMS 14 C ages in that core.…”

“…The interlocking coral branch framework in turn acts to stabilize the sediments on and below the seafloor, limiting sediment mixing such as by internal waves or bioturbation. With sustained food and sediment supply promoted by strong hydrodynamics and turbulent conditions as well as adequate physico-chemical conditions, CWC mounds can develop for thousands to millions of yearsrecording in some cases multiple phases of coral growth and mound formation (Kano et al, 2007;Wienberg et al, 2018;Raddatz et al, 2020;Corbera et al, 2021;Fentimen et al, 2022). Consequently, CWC mounds provide an important archive to study the history of CWC reefs and their diversity.…”