Annotated record of the detailed examination of Mn deposits from DSDP Site 42, Leg 5 (Cores 5-42-5, 5-42-6, 5-42-9)

Site 42 is one of the series of sites selected by the Pacific Advisory Panel along the 140th meridian to sample the longitudinal variation in sediment composition in the eastern Pacific. The site is located in an area of abyssal hills between the Clarion and Clipperton Fracture Zones, and is at the northern margin of the thick development of acoustically transparent sediment extending along the equator.

Annotated record of the detailed examination of Mn deposits from DSDP Site 40, Leg 5 (Cores 5-40-1, 5-40-11)

Site 40 was located by the JOIDES Pacific Advisory Panel in the region between the Molokai and Clarion Fracture Zones with the objective of recovering a continuous sediment core for the paleontologic and biostratigraphic study of the variation in sediment components at the transition between the North Pacific gyral and the Equatorial Current System.

Annotated record of the detailed examination of Mn deposits from DSDP Site 39, Leg 5 (Cores 5-39-1, 5-39-2)

Site 39 was located in the region between the Pioneer and Murray Fracture Zones, with the objective of recovering a continuous sediment core for paleontologic and stratigraphic study of the longitudinal variations in sediment components in the eastern Pacific. This site was selected, together with the adjacent ones in the north-south line along 140°W, to provide information on the geologic history of the North Pacific gyral, insofar as this might be recorded in the sediments.

Annotated record of the detailed examination of Mn deposits from DSDP Site 33, Leg 5 (Core 5-33-2)

The proposed location of Site 33 was over north-south Magnetic Anomaly 10 (Pittman-Heirtzler, 32 million years) in order (a) to provide a basis for comparison of the age of the basal sediments with the age based on the magnetic anomaly, (b) to provide a basis for evaluation of relative movement along the Pioneer and Mendocino Fracture Zones, and (c) by being paired with Site 34, to provide comparison of basement materials for adjacent positive and negative magnetic anomalies.

Annotated record of the detailed examination of Mn deposits from DSDP Site 41, Leg 5 (Cores 5-41-1, 5-41-5)

Site 41 marks the transition from the North Pacific gyral to the Equatorial Current System. The JOIDES Pacific Advisory Panel selected a site at this latitude along the longitudinal profile of 140°W in order to obtain information on the history of migrations of these current systems.

Annotated record of the detailed examination of Mn deposits from DSDP Site 34, Leg 5 (Core 5-34-17)

Site 34 had been located by the JOIDES Pacific Advisory Panel to be over a negative magnetic anomaly (31 million years B.P.) immediately to the east of Anomaly 10 (Site 33). The primary objective was to obtain samples of basement and basal sediment to provide comparison between adjacent positive and negative magnetic anomalies. A second objective was to obtain samples which would permit an analysis of the variability in sediment over relatively short distances (about 10 miles). Although basement had not been reached at Site 33 because of the unexpected chert, the use of a massive diamond bit at Site 34 permitted coring through the chert to basement at 383 meters below the sea floor. Even though the near basement sections of the paired sites (33 and 34) could not be compared, comparison would be possible above the chert layer.

Annotated record of the detailed examination of Mn deposits from DSDP Site 37, Leg 5 (Cores 5-37-1, 5-37-2)

The JOIDES Pacific Advisory Panel proposed Site 37 to meet two principal objectives: to determine the significance of the magnetic anomaly pattern, and the longitudinal profile of the sediment sequence in the eastern Pacific. Site 37 was to be located on the same magnetic anomaly as was Site 33 (#10, 32 million years age), for comparison across the intervening Mendocino Fracture Zone. As basement had not been reached at Site 33, this objective could not be met specifically. However, sediment comparison across the fracture zone was possible.

Annotated record of the detailed examination of Mn deposits from DSDP Site 32, Leg 5 (Cores 5-32-13, 5-32-14)

Site 32 was proposed by the Pacific Advisory Panel at a location over a strong positive magnetic anomaly (Number 13 on the Pittman-Heirtzler scale, 38 million years) where samples of the basement and the basal sediment would be of value in testing hypotheses for origin of the linear magnetic anomalies from this part of the Pacific. Comparison of this site, south of the Pioneer Fracture Zone, with later sites north of the Fracture Zone would be the basis for evaluating the discontinuity formed by the Pioneer.

Annotated record of the detailed examination of Mn deposits from DSDP Site 38, Leg 5 (Cores 5-38-6)

The nonfossiliferous nature of most of the thin sediment sequence at Site 37 had provided little biostratigraphic information for the northern end of the proposed section of sites along 140°W longitude. In an attempt to provide a biostratigraphically more meaningful hole as the high latitude terminus of the meridional section, an additional site (Site 38) was drilled between the Mendocino and Pioneer Fracture Zones.

Annotated record of the detailed examination of Mn deposits from DSDP Site 24, Leg 4 (Core 4-24-1)

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.

Annotated record of the detailed examination of Mn deposits from DSDP Site, Leg 4 (Cores 4-27-1 and 4-27A-1)

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.

Annotated record of the detailed examination of Mn deposits from DSDP Site 25, Leg 4 (Core 4-25A-1)

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.

Annotated record of the detailed examination of Mn deposits from DSDP Site 26, Leg 4 (Core 4-26-1)

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.

Annotated record of the detailed examination of Mn deposits from DSDP Site 29, Leg 4 (Hole 4-29B)

The southern Caribbean basins are thought to be part of a relatively old and geologically stable crustal plate. Although surrounded by belts of high earthquake activity, the central Caribbean is seismically quiet. The region also constitutes a quiet magnetic zone and appears to have resisted all of the surrounding forces related to ocean floor spreading. In addition to providing considerable information on the general geologic history of the Caribbean region, paleontologic studies on cores at Site 29 were expected to provide valuable data on phylogenetic trends within the planktonic foraminifera and calcareous nannoplankton, furnishing more accurate criteria for intercontinental stratigraphic correlation. The work reported here is a biostratigraphic summary of available samples. only the most important and biostratigraphically significant components of the faunas have been noted. No attempt has been made to give an exhaustive faunal analysis of the samples seen.