ALBERT

Description: The drilling objectives at this site were to complete the cored section begun at Site 23 in accordance with the recommendations of the JOIDES Atlantic Advisory Panel, presented in the Site 23 report. The location coincides with a position on the southeastern side of the elevated portion of basement in this area.

Description: At the Leg 4 pre-cruise meeting in Miami, Florida, in January 1969, the Ridge site was proposed as an additional site to be investigated, if possible. Since the water depth and sediment thickness at this site were both minimal (2000 meters and less than 100 meters, respectively) and the location was not far from the track between initially planned sites, the shipboard party decided, upon completion of work at Site 24, to make a 24-hour drilling effort on the North Brazilian Ridge. The drilling objectives at this location were to sample and date the sediments atop the Ridge crest and to determine the nature, age and origin of the consolidated material beneath the thin mantle of sediment.

Description: The northern margin of the Demerara Abyssal Plain is bordered by a low ESE-WNW trending rise known as the Barracuda Ridge. North of South America, the eastern margin of the Demerara Abyssal Plain is formed by the Barbados Ridge. An extensive sedimentary section of the Barbados Ridge is exposed on the island of Barbados and consists of a series of radiolarian to planktonic foraminiferal and calcareous nannofossil biogenic sediments interlayered with ash beds. To determine the nature of the sediments and "basement," Site 27 was selected on the northern margin of the Demerara Abyssal Plain, south of the Barracuda Ridge.

Description: Site 26 was selected on the crest of the Mid-Atlantic Ridge between 15°N and 5°S is offset to the east nearly 4000 kilometers through a series of fracture zones. One of the most prominent of these is the Vema Fracture Zone, a narrow east-west trending trough which cuts through the Mid-Atlantic Ridge at latitude 11°N.

Description: The cores recovered by the Deep Sea Drilling Project provide a reservoir of material for paleontologic investigation, offering unparalleled opportunities to learn about the global aspects of biostratigraphy, paleobiogeography, paleoecology, paleoclimatology, paleoproductivity, changes in ocean-water chemistry, and diagenetic processes. At the time of inception of the Deep Sea Drilling Project, marine plankton fossil groups were poorly known except for the planktonic Foraminifera. In the past few years, the calcareous nannoplankton also have been used to establish zonations for Jurassic to Holocene strata, and a radiolarian zonation of the Cenozoic has been worked out. It is now feasible to evaluate differences in age-equivalent fossil assemblages in the different areas of the ocean, in different climatic zones, at different depths, and in different sediment types. Biogeographic differences, particularly between the southern ocean and the North Atlantic and North Pacific, have been detected. Distinct climatic zonation of the oceans became well established during the Late Cretaceous and has been subject to periodic intensification during the Cenozoic, with the end of the Cretaceous, end of the Eocene, and the Pliocene being times of especially rapid change and evolution. Accumulations of siliceous ooze indicate regions of high productivity. Dissolution of calcareous pelagic fossils is selective, removing some species from the assemblage before others are attacked; this phenomenon offers a method of determining fluctuations of the calcium carbonate compensat on depth, and a means of investigating diagenetic processes in deep-sea sediments.