Description: Cameras were mounted in a newly designed corehead of a piston corer and used to photograph coring operations during 36 stations on CHAIN cruise 75 and 28 stations on ATLANTIS II cruise 42. Through the analysis of these photographs, the deep-water operation of a piston corer during its descent, tripping, impact with the bottom, and ascent has been studied, providing information on the corer's stability, effectiveness in obtaining a bottom sample, and influence on the nearby sea-floor. Accurate determinations of the amount of penetration were possible, allowing comparisons to be made with the more indirect methods of determining penetration and with the length of core recovered. Sediment clouds produced by bottom currents were noticed in many of the bottom photographs. A number of suggestions are made for future piston coring operations. The corer descends with little rotation and swinging. Free-fall and penetration generally take place in less than 5 seconds, with a rotation of 20-60° and an increase of about 6° in vertical deviation. During penetration, the corer disturbs the surrounding sea floor, producing both mounds and depressions around the core barrels. While resting in the bottom, the corer is very stable although some wobbling does occur. Considerable rotation takes place during both pull-out and ascent; frequent sediment discharges from the piston corer occur. No consistent relationship was found between the amount of penetration and the length of core recovered, and thus with the degree of core shortening. Comparisons between piston and pilot cores indicate that the piston cores have been shortened and disturbed relative to the pilot cores, and that as much as a meter of the upper portion of the piston core has been lost. The position of the mud-mark appears to be a reliable indicator of the amount of penetration; estimates by extrapolation of the thermal gradient to the surface are less reliable. The vertical deviation of the corer in the bottom does not influence the amount of penetration. Stratigraphic dips in the recovered cores correspond poorly to this vertical deviation in the bottom.

Description: The National Science Foundation Grants GA-1077 and GA-1209 and submitted to the Office of Naval Research under Contract Nonr-4029(00); NR 260-101, and N00014-66-C0241; NR 083- 004.

Description: Unlike most previous Deep Sea Drilling Project cruises, Leg 39 was not scientifically planned as a "theme" cruise, on which a number of sites are drilled to address a single scientific problem area, namely, to improve our knowledge of paleocirculation changes and the overall geologic history of the South Atlantic Ocean. This would be done along more specific objectives: 1) collect a biostratigraphic section on the Ceará Rise (Site 354), determine the nature and age of a prominent reflector there, and determine the nature and age of basement; 2) date basement between magnetic anomalies 32 and 33 in the Argentine Basin (Site 358), and 33 and 34 in the Brazil Basin (Site 355); obtain as complete sedimentary sections as time would permit at the Ceará Rise, Brazil Basin, the Argentine Basin and Sào Paulo Plateau (Site 356).

Description: The results of lithologic, petrographic, grain-size, and chemical studies of volcaniclastic sediments recovered during Leg 107 of the Ocean Drilling Program show that a variety of volcaniclastic sediments occur in the Tyrrhenian Basin. The abundance of volcanic glass and presence (or lack) of sediment structure is used to classify the sediments into four sediment-deposit types: (1) tephra fall, (2) volcaniclastic turbidite, (3) debris flow, and (4) volcanic sand. The abundance and distribution of these sediment types at Leg 107 sites are related both to proximity to volcanic sources and pathways of sediment transport to the basin floor. Deposits directly related to volcanic events include tephra fall, debris flow, and some volcaniclastic turbidites. The latter are generated from reworking of tephra fall and from pyroclastic gravity flows that entered the sea at the time of (primary), or closely following (epiclastic), eruption. These turbidites occur throughout the basin, are glass-rich, and are most common in the central and southeastern portions of the basin. A large debris flow encountered at Sites 651 and 650 represents a marine-deposited equivalent of the Campanian Ignimbrite, a large pyroclastic deposit in the Phlegrean Fields produced about 38,000 yr ago. This correlation is confirmed by glass chemistry. Volcanic sands and other volcaniclastic turbidites represent, on the other hand, deposits of more extensively reworked pyroclastics. Heterogeneous volcanic glass and mineral population, abundant detrital crystals, and, occasionally, high clay component attest to the secondary (epiclastic) origin of these deposits. Several large volcanic sands that occur immediately above vitric-rich layers may be derived directly from reworking of the vitric-rich layer, although predominantly in the nearshore and/or shelf environment. Glass chemistry shows that volcaniclastic sediments at Leg 107 sites are mainly of local provenance. At westerly Sites 655 and 653 rhyolitic and trachytic glasses have a source in the nearby Pontine Archipelago. In the central part of the basin at Site 651, volcaniclastic sediments are primarily derived from the Campanian volcanic province. At southerly Site 650 provenance is mainly the Eolian Arc. Two major volcaniclastic turbidites at Site 650 contain calc-alkaline rhyolitic glass, documenting large eruptions of rhyolitic magma not before reported in the arc.