Late Quaternary Climatic Reconstruction Using the Deep-Water Coral Desmophyllum cristigalli

Abstract

<p>In 1978, the Bedford Institute of Oceanography dredged dead specimens of the solitary, deep-water, ahermatypic coral Desmophyllum cristigalli from the top of Orphan Knoll, at a depth of 1700 m. The collection lay unstudied until last year. Dating of several individuals by uranium- thorium and 14c shows that the retrieved corals ranged in age from 70,000 to 4,000 y BP. One especially large specimen lived from 12,000 to 11,000 y BP. Detailed analysis of the 𝛿18O stratigraphy of this long-lived coral shows that the Younger Dryas climatic event is preserved as an abrupt shift of >2 per mil, which suggests a profound change in the saline circulation. It also supports the theory that massive ocean-atmosphere reorganizations trigger glacial cycles - specifically, in the North Atlantic, via the shutdown of the Gulf Stream 'heat conveyor'. Estimations of coral-growth rates give a good indication of the rapidity of the Younger Dryas onset: it is possible that the transition from interglacial to glacial conditions may have occurred with 15 years. Many climatic reconstructions to date have been based on the foraminiferal record, but solitary corals are likely to be far superior recorders of paleoenvironmental conditions because of their immunity to bioturbation and largescale transport.</p>