Contributors:Prell, Warren L., Gardner, James V., Adelseck, Charles, Blechschmidt, Gretchen, Fleet, Andrew J., Keigwin, Lloyd D., Kent, Dennis V., Ledbetter, Michael T., Mann, Ulrich, Mayer, Larry, Reidel, William R., Sancetta, Constance, Spariosu, Dann J., Zimmerman, Herman B.
Leg 68 of the Deep Sea Drilling Project used the newly developed Hydraulic Piston Corer (HPC) to recover two virtually continuous, undisturbed sections of late Neogene and Quaternarysediment. The sites are located in the western Caribbean (Site 502, 4 holes) and in the eastern equatorial Pacific (Site 503, 2 holes). The sediment of Site 502 is primarily foram-bearing nanno marl which accumulated at about 3 to 4 cm/thousand yr. The bottom of Site 502 (228.7 m) is ~8 m.y. old. The sediment of Site 503 is primarily siliceous calcareous ooze which accumulated at about 2 to 3 cm/thousand yr. The bottom of Site 503 (235.0 m) is ~8 m.y. old. The magnetostratigraphy of both sites was determined on the R.V. Glomar Challenger with a long-core spinner magnetometer. All paleomagnetic boundaries through the Gilbert were identified in Site 502; most of them were identified in Site 503. The sediment at both sites shows a distinct cyclicity of calcium carbonate content. These relatively high accumulation rate, continuous, undisturbed HPC cores will enable a wide variety of high-resolution biostratigraphic, paleoclimatic, and paleoceanographic studies heretofore not feasible.
Contributors:Zimmerman, H. B., Shackleton, N. J., Backman, J., Kent, Dennis V., Baldauf, J. G., Kaltenback, A. J., Morton, A. C.
DSDP Hole 552A, cored with the HPC on Hatton Drift, represents an almost complete and undisturbed sediment section spanning the late Neogene and Quaternary. Lithologic, faunal, isotopic, and paleomagnetic analyses indicate that the section represents the most complete deep sea record of climatic evolution hitherto recovered at high latitudes in the northern hemisphere. A glacial record of remarkable resolution for the late Pliocene and Pleistocene is provided by oxygen and carbon isotope ratios in benthic foraminifers. In the upper part of the section, the whole of the standard oxygen isotope record of the past million years is well preserved. The onset of ice-rafting and glacial-interglacial alternations occurs at about 2.4 m.y. ago.
Contributors:Prell, W. L., Gardner, J. V., Kent, Dennis V.
The sixty-eighth cruise of Glomar Challenger was devoted to using the newly developed Hydraulic Piston Corer (HPC) to recover undisturbed, continuous sequences of unlithified sediment. We returned to the vicinities of two rotary-drilled sites (83 and 154). The stratigraphy of these sites indicated that uninterrupted sections of late Neogene and Quaternarysediment should exist at these locations. The ship left Curacao, Dutch Antilles, on 13 August 1979, cored for 11 days at Site 502, and transited from the Caribbean through the Panama Canal. Site 503, in the eastern equatorial Pacific, was cored for seven days, and we then finally transited to Salinas, Ecuador. The results of this cruise (reported in this volume) include preliminary descriptions, based primarily on shipboard observations and analyses, of the material recovered (site chapters) and additional studies performed ashore after the cruise, either by scientists who participated in the cruise or by other invited investigators. The main purpose of this volume is to present not an exhaustive study of the sediment recovered but rather a description, as detailed as possible, of the material recovered on Leg 68 accompanied by interpretations and conclusions that remain preliminary.