Cold-Water-Carbonates in the Bay of Biscay
Marine carbonates are widely used archives for paleoceanographic and climatic reconstructions. The cold-water carbonates investigated in this study are skeletal remains of the two cold-water coral (CWC) species Lophelia pertusa and Madrepora oculata. These framework-building scleractinian coral spec...
| Summary: | Marine carbonates are widely used archives for paleoceanographic and climatic reconstructions. The cold-water carbonates investigated in this study are skeletal remains of the two cold-water coral (CWC) species Lophelia pertusa and Madrepora oculata. These framework-building scleractinian coral species are widespread on the continental slopes of the world’s oceans and their aragonitic skeletons can be precisely dated with radiometric techniques, which makes them an interesting archive. In the northeast Atlantic CWCs are known to build different ecosystems. While reefs in Norway, mound structures off the coast of Ireland and CWC occurrences in the Gulf of Cadiz are relatively well studied, comparably little is known about the Bay of Biscay, a region that connects the eastern temperate Atlantic with the more northern regions. In order to examine the CWC distribution and its history in the Bay of Biscay, this study analyzes coral samples from six sediment cores that were retrieved during METEOR Cruise M84/5 in June 2011 along a depth transect (539mbsl - 980mbsl) in the St. Nazaire canyon in the northern Bay of Biscay. In this setting CWCs currently occur in patches and thickets and not in large reefs like they are e.g. known from the Norwegian coast. The aim of tthis study is to examine the CWC growth in the St. Nazaire canyon, determine how long CWCs have been growing in this setting and reconstruct under which environmental conditions they lived. For this purpose the coral samples were mechanically and chemically cleaned, dated via the U/Th-decay chain and analyzed for their skeletal stable isotope and element ratios. The measurement of these ratios was carried out on a Quadrupole Inductively Coupled Plasma Mass Spectrometer (Q ICP-MS). The dating of the samples revealed coral ages from 12,5 kyBP to present-day ages. This shows that since the end of the last glacial the St. Nazaire canyon represented a suitable setting for CWC growth. While other CWC ecosystems further south, e.g. in the Gulf of Cadiz, seem to ... |
|---|