Cold-water corals of the Northeast Atlantic margin: Archives of intermediate water circulation during the Holocene
Frank, N.; Paterne, M.; Ayliffe, L.; Lutringer, A.; Blamart, D.; Henriet, J.P.; van Weering, T. (2003). Cold-water corals of the Northeast Atlantic margin: Archives of intermediate water circulation during the Holocene. Erlanger Geol. Abh. Sonderband 4: 37
In: Erlanger Geologische Abhandlungen. Institut für Geologie der Universität Erlangen-Nürnberg: Erlangen. ISSN 0071-1160
We present combined 230Th/U and 14C dating and stable isotope analyses on benthic corals from the northeastern North Atlantic in order to investigate past changes of the thermohaline circulation. The reef forming cold-water corals Lophelia pertusa and Madrepora oculata were raised from intermediate depth (~750m bsl) from carbonate mounds along Rockall and Porcupine Bank and Porcupine Seabight. The 230Th/U ages range from today to 247400yr. The d234U, 230Th/232Th and X-ray images indicate negligible alteration of the investigated corals, i.e. open system behavior. Very young deep-sea corals were accurately dated by means of 230Th/U dating. One in situ living Lophelia coral yielded a mean age of 1995AD, matching the date of collection in 1999AD. From this coral. the measured and calculated seawater d14C values are indistinguishable and the reservoir age Rinterm of the upper intermediate waters is 710±80 years. Several modern corals, being dated between 1950AD and 1986AD, recorded the atmospheric 14C/12C increase due to the nuclear tests in the early 60s. The modern pre-bomb d14C value of the North Atlantic intermediate waters was determined at an average of -65±7‰, and the mean reservoir age at 448±62 years. Finally, several investigated benthic coral grew during the second step of the deglaciation and during the Holocene climate optimum (from 10900 to about 8000 CAL yr BP). The reservoir age of average 500±150 years is equivalent to that of today indicating that, during the studied coral growth episodes, a modern type oceanic circulation, as well as the air-sea and surface to deeper adjacent water 14CO2 exchanges prevaled in the Northeast Atlantic Ocean.
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