Biological matter as a source for Cenozoic deep-sea sediments in the Equatorial Pacific

Deep sea sediments contain more Cu, Ni, Ba, B etc., than transport of detrital terrigenous matter (TM) can explain. Longdistance transport in dissolved from is of no importance for many of these elements. Marine biological matter (BM) is enriched in Cu, Ni, Ba, B etc. Conservative mixing models, using BM and TM as inputs show that the compositional variations in pelagic sediments can be explained by these sources. Such mixing models have been used to estimate how the influx of BM and TM have varied with time, and to what extent different elements ares upplied by BM and TM. The results show that in Cenozoic Equatorial Pacific sediments CaCO₃, opaline silica, B, Ba, and Cu are predominantly biogenous. It is probable that also P and Ni belong to this group of elements, whereas almost all Al, Ti, Zr, V and Mn are delivered by TM or some volcanic processes. The accumulation rates (AR) for the biological constituents reached maxima during the L. Oligocene and the Miocene, and minima during the U. Oligocene and the Pleistocene; some AR from the Oligocene and the Miocene being 3-6 times higher than at present. The accumulation rate patterns for opaline silica, Ba and B co-vary, whereas the AR for CaCO₃ show another time dependance pattern. These AR-patterns are probably partly due to climatic variations. Plankton in Pacific Equatorial waters incorporate much more Cu, Ni, etc., than is required for the particulate transport of these elements to the ocean floor. This suggests that transport in particulate form of BM is an important source of Cu, Ba, B, etc. for the deep sea floor.