The 2.6 Ma depositional sequence from the Challenger cold-water coral carbonate mound (IODP Exp. 307): Sediment contributors and hydrodynamic palaeo-environments

The Dangeard and Explorer canyons, South Western Approaches UK: Geology, sedimentology and newly discovered cold-water coral mini-mounds

“…Wheeler et al (2011) propose that the process of merging of individual mounds and clusters of mounds through continued growth may result in the formation of coral carbonate mounds, thus like the Moira Mounds which may represent an early growth phase for carbonate mounds, the mini-mounds of this study may represent a short-lived period of mound building. The process of accretion of these larger mounds is not well understood although coring through the Challenger Mound by IODP Expedition 307 revealed gradual reef stacking over the course of 2.6 Ma but the record is discontinuous with glacially derived sediments often missing (Huvenne et al, 2009a andThierens et al, 2009). It is unknown at this point whether the CWC mini-mounds of the Dangeard and Explorer provinces are relict due to a change in environmental conditions and therefore unlikely to support new coral growth even if fishing pressure were to be removed, or if trawling damage is solely to blame for the coral rubble in the area. If conditions were right, it is possible that the mounds may return to a more active and healthy state if fishing pressure was removed as dead coral framework is believed to offer a suitable substrata for renewed growth (Roberts et al, 2006).…”

“…The process of accretion of these large mounds is not well understood although coring through the Challenger Mound by IODP Expedition 307 revealed gradual reef stacking over the course of 2.6 Ma. However, the record is discontinuous with glacially derived sediments often missing (Huvenne et al, 2009a andThierens et al, 2009). Smaller CWC mounds, often termed 'mini-mounds', are also documented, such as the Moira Mounds that are 20-35 m in diameter and 3-11 m high and form part of the Belgica Mound province (Wheeler et al, 2011).…”

“…The Moira Mounds may serve as an analogue for mini-mounds, up to 5 m high, observed on Odet Spur located between Odet Canyon and Guilvinec Canyon . The Moira Mounds have no sub-surface expression so are proposed as initiated during Holocene times and it is suggested that the coalescence of individual mounds, or clusters of mounds, may result in the formation of large coral carbonate mounds, examples of which are located nearby, such as the Challenger Mound ( Huvenne et al, 2009a, Thierens et al, 2009and Wheeler et al, 2011.…”

Carbonate mounds: From paradox to World Heritage

“…Yet, ocean drilling on the Irish margin soon revealed the extraordinary significance of cold-water coral mounds, for instance as high-resolution environmental archive (IODP Exp. 307, Ferdelman et al, 2006;Foubert and Henriet, 2009;Thierens et al, 2010). As developed later, they may hold -far more than the shallow-water carbonate factory -a key to the dynamics of deep and intermediate water circulation, heartbeat of the Earth's climate machine.…”

Cold-water coral carbonate mounds as unique palaeo-archives: the Plio-Pleistocene Challenger Mound record (NE Atlantic)

“…1) offers a new perspective. Not only did it recover the first complete sequence through a coral carbonate mound (documenting mound initiation till decline; Ferdelman et al, 2006), the 155 m long PleistoceneeHolocene Challenger Mound cores also exposed a ca 132 m long, semi-continuous Early Pleistocene (2.6e1.7 Ma) record of alternating current-influenced and ice-rafted deposits from the mid-latitudinal NE Atlantic margin (Thierens et al, 2010). Considering the dynamic, erosive/non-depositional environment established along the NW European continental margin during the Early Pleistocene (e.g.…”