Correlation, frequency of emplacement and source directions of megaturbidites on the Madeira Abyssal Plain

Abstract

This paper describes the sediments of the whole Madeira Abyssal Plain including the MADCAP area to the south. Previous studies have centred on the central sub-basin which occupies most of the plain and which has become one of the most studied areas of seafloor. The plain is made up of a series of large turbidites separated by thin pelagic layers which can be used to provide a high resolution stratigraphy back to about 750,000 years. Many of the turbidites were deposited close to oxygen isotope stage boundaries suggesting a strong relationship to sea-level/climate change, although the exact initiation mechanism for the flows is not known. Data from the northern and southern extensions of the plain shows the effects of different entry points for the four main turbidite groups; volcanic rich turbidites enter from the NE and E, calcareous turbidites from the W, one group of organic rich turbidites enters from the SE and one group from the NE and E. Different turbidite sources operate for limited periods before switching to one of the other source areas. It is very rare for two sources to provide turbidites at the same isotope stage boundary.