The Deep-Sea Canyons in the Gulf of Guinea Near Fernando Póo

Summary

Two canyons descending from the shelf west of the island of Fernando Póo were followed to the deep ocean. They appear to terminate 110 nautical miles (200 km) from the shelf break in a water depth of 2800 m. A little further downslope, a new channel is formed which continues to descend over a distance of about 400 nautical miles (700 km) to a water depth of 4700 m. The sediments in this channel were found to be covered with a thin layer of Holocene clays. Beneath this recent cover, the canyon bottom is predominantly sandy and the natural levees predominantly clayey. The canyon-bottom sands are clean, moderately well sorted and mostly medium sized. Their greatest surface distribution occurs near the end of the channel where it widens before petering out at the lower end of the continental rise. No sands were found in the cores from the adjoining abyssal plain.

The majority of the sands have not been brought into the area by the Niger river, but have been derived from a region east of the Niger drainage area.