Radioactive and magnetic investigations

Age and growth pattern determination of manganese nodules were explored. Two methods are discussed: (1) measurement of the presence of radioactive iodine isotopes; which is effective only up to 3.105 years, and (2) measurements of magnetism. The growth rates of three nodules were determined. The surface of the nodule was recent, and the overall age of the nodule could be determined with accuracy of better than 30%. Measurement of paleomagnetic effect was attempted to determine wider age ranges, however, the measured sign changes could not be interpreted as paleomagnetic reversals

High-resolution stratigraphy and the response of biota to Late Cenozoic environmental changes in the central equatorial Pacific Ocean (Manihiki Plateau)

An undisturbed 16 m late Pliocene-Pleistocene sediment core spanning 2.6 Myr of deposition was recovered from the Manihiki Plateau by the German research vessel Sonne in 1990. This core 34KL complements the heavily disturbed late Pliocene-Pleistocene core sections of DSDP Site 317, and is well suited for stratigraphic correlation. The sediments consist of calcareous microfossils (93–97% CaCO3), minor portions of siliceous microfossils and detrital minerals. All important calcareous microfossil zones could be identified and correlated with the magnetostratigraphic and isotope stratigraphic events, stages and periods. Due to the high degree of silica dissolution, the late Quaternary radiolarian Buccinosphaera invaginata Zone is the only siliceous fossil zone which could be identified. An interval with Globigerinoides gomitulus/pink was found within the middle Pleistocene which is clearly distinguished from the Globigerinoides ruber/pink interval of the late Pleistocene. The magnetostratigraphic Gauss-Matuyama and Matuyama-Brunhes boundaries as well as the Olduvai and Jaramillo events were clearly identified. The δ180 curve displays the 100 kyr (Milankovitch) and the 41 kyr (Laplace) cyclicity periods. The beginning of the Laplace Period and the last occurrence of the calcareous nannofossil Discoaster brouweri, which marks the end of the Pliocene, fall within the base of the Olduvai Event. There is also a marked drop in sedimentation rates around this time, which seems to be a regional phenomenon. Prominent 3.5 kHz subbottom reflectors at 8 ms and 15 ms reflection time are related to lithologic changes near the Mid-Pleistocene Revolution (MPR) and the beginning of the Laplace Period or the Pleistocene, respectively. It is possible to trace these reflectors laterally to the eroded eastern edge of the Manihiki Plateau where they can be tied to older strata

Neodymium isotope constraints on provenance, dispersal, and climate-driven supply of Zambezi sediments along the Mozambique Margin during the past ∼45,000 years

Marine sediments deposited off the Zambezi River that drains a considerable part of the southeast African continent provide continuous records of the continental climatic and environmental conditions. Here we present time series of neodymium (Nd) isotope signatures of the detrital sediment fraction during the past ~45,000 years, to reconstruct climate-driven changes in the provenance of clays deposited along the Mozambique Margin. Coherent with the surface current regime, the Nd isotope distribution in surface sediments reveals mixing of the alongshore flowing Zambezi suspension load with sediments supplied by smaller rivers located further north. To reconstruct past changes in sediment provenances, Nd isotope signatures of clays that are not significantly fractionated during weathering processes have been obtained from core 64PE304-80, which was recovered just north of the Zambezi mouth at 1329 m water depth. Distinctly unradiogenic clay signatures (ENd values <214.2) are found during the Last Glacial Maximum, Heinrich Stadial 1, and Younger Dryas. In contrast, the Nd isotope record shows higher, more radiogenic isotope signatures during Marine Isotope Stage 3 and between ~15 and ~5 ka BP, the latter coinciding with the timing of the northern hemisphere African Humid Period. The clay-sized sediment fraction with the least radiogenic Nd isotope signatures was deposited during the Holocene, when the adjacent Mozambique Shelf became completely flooded. In general, the contribution of the distinctly unradiogenic Zambezi suspension load has followed the intensity of precession-forced monsoonal precipitation and enhanced during periods of increased southern hemisphere insolation and high-latitude northern hemispheric climate variability

CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

Schwermineraluntersuchungen an Sedimenten aus West-Pakistan sowie vom angrenzenden Schelf

Sediment samples from southern West-Paldstan and the adjacent shelf have been studied for their heavy mineral contents and compositions. lt is shown that the sediment load of the Indus river has influenced the sedimentation in the shelf areas south, southwest and in front of the Indus delta to a greater extent than in northerly direction. In the northern shelf region the smaller local rivers have dominated the marine sedimentation

Geochemistry, grain-size distribution and smear slide abundances at DSDP Holes 68-501, 69-504 and 69-505

Rapidly deposited Miocene and younger siliceous and calcareous sediments at Sites 504 and 505 in the central Panama Basin near the eastern end of the equatorial high productivity belt exhibit marked lithologic variation with increasing depth. At both sites, the sediments are particularly calcareous just above the basaltic basement and were deposited at the highest accumulation rates. Sediments distinctly lower in carbonate and richer in clayey and siliceous components were deposited in the late Pliocene, a period characterized by lower accumulation rates. The sediments became somewhat more calcareous again in the Pleistocene, when accumulation rates rose again. Accumulation rates at Site 505, which is 77 km north of Site 504, have been enhanced by redeposition from surrounding basement highs, but the patterns of the accumulation rates at the two sites are similar. The lithologic variations reflect the sensitive interplay of crustal subsidence, fluctuations in the calcite compensation depth, and changes in the geographic location or the quantity of surface-water productivity. Computations using the bulk sediment composition of samples from Site 504 show that the rate of accumulation of biogenic silica increased nearly fourfold during the upper Pliocene, despite the drop in carbonate and overall accumulation rates. This could be explained by the shoaling of the calcite compensation depth beneath a zone of very high surface productivity, which would increase the carbonate dissolution in the water column but leave biogenic opal comparatively unaffected. Chemical data for the sediments also show a slight enrichment in Mn, Fe, Cu, Zn, and other trace metals at about this time, reflecting increases in both hydrogenous and metalliferous ("hydrothermal") components. The biological fixation of seawater sulfate as pyrite, in combination with the high sediment accumulation rates, probably contributed to the enrichment of some of the trace metals. Chemical data also show that several of the Pleistocene and one of the lower Pliocene ash beds are rhyolitic in composition and represent material derived from the South American eruption of ignimbrites. In all beds except these, however, bioturbation has dispersed ash to uniform and low abundances in the sediments. Sites 504 and 505 are in contrasting locations of high and low heat flow, respectively. Temperatures near 50°C just above basalts at Site 504 have promoted the formation of chert bands intercalated with limestone in the 30 meters above the basalts and have accelerated the induration of nearly 90 meters of sediments above the cherts to chalk. The thickness of the sediments at Site 505 is similar, but the sediments remain oozes nearly down to basement, where temperatures are only about 9°C