Morphological variability of Globorotalia menardii in DSDP Sites 68-502 and 68-503

Variability in the test of Globorotalia menardii during the past 8 million years has been investigated at DSDP Site 502A (Caribbean Sea) and DSDP Site 503A (Eastern Equatorial Pacific). Measurements were made of spire height (delta x), maximum diameter (delta y), the tangent angles of the upper and lower peripheral keels (phi 1, phi 2, respectively), the number of chambers in the final whorl, and the area of the silhouette in keel view. Four morphotypes alpha, beta, gamma, and delta were distinguished. Morphotype alpha was found in strata ranging in age from the Late Miocene through the Holocene. It shows a continuous increase in delta x and delta y until the Late Pleistocene. During and after the final closure of the ancient Central American Seaway (between 2.4 Ma and 1.8 Ma) there was a rapid increase in the area of the test in keel view. At the Caribbean Sea site, morphotype beta evolved during the past 0.22 Ma. It is less inflated than alpha and has a more delicate test. In the morphospace of delta x vs. delta y, morphotypes alpha and beta can be distinguished by a separation line delta y = 3.2 * delta x - 160 (delta x and delta y in µm). Plots of morphotype alpha are below that line, those of beta are above it. Morphotype alpha is taken to be Globorotalia menardii menardii Parker, Jones & Brady (1865) and includes G. menardii 'A' Bolli (1970). Morphotype beta is identified as G. menardii cultrata (d'Orbigny). Morphotypes gamma and delta are extinct Upper Miocene to Pliocene forms which evolved from morphotype alpha. They have a narrower phi 1 angle and more chambers (>=7) than morphotype alpha commonly with 5 to 6 chambers (7 in transitional forms). In contemporaneous samples morphotype delta can be distinguished from gamma by a smaller value of phi 1 and 8 or more chambers in the final whorl. Morphotype gamma is taken to be G. limbata (Fornasini, 1902) and includes the junior synonym G. menardii 'B' Bolli (1970). Morphotype delta is G. multicamerata Cushman & Jarvis (1930). With the exception of the Late Pleistocene development of G. menardii cultrataonly in the Caribbean the morphological changes of G. menardii at DSDP Sites 502A and 503A are similar. The development from the ancestral G. menardii menardii of the G. limbata - G. multicamerata lineage during the Pliocene and of G. menardii cultrata during the Late Pleistocene suggests responses at the two sites to a changing palaeoceanography during and after the formation of the Isthmus of Panama.

Stable carbon and oxygen isotope ratios of calcareous dinoflagellate cysts and planktic foraminifera from the Campanian/Maastrichtian section of ODP Hole 113-690C in the Weddell Sea (Table 1)

Delta18O and delta13C values for the calcareous dinoflagellate species Orthopithonella? globosa (Fütterer 1984) Lentin and Williams 1985 and Pirumella krasheninnikovii (Bolli 1974) Lentin and Williams 1993 from lates Campanian and earliest Maastrichtian of ODP Hole 690C (Weddell Sea, Antarctic Ocean) have been studied in order to evaluate the species' depth habitat in the water column and their applicability in paleoceanographic studies. The calcareous dinoflagellates show isotopic values comparable to probably shallow-dwelling planktic foraminifera from the same sample in delta18O, but have an offset of about -5 ? to -7? in delta13C. This suggests that calcareous dinoflagellate oxygen isotopes may provide information for paleoceanographic reconstructions of sea-surface water temperatures, whereas their extremely light carbon isotope values are probably due to photosynthetic processes.

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.