Accumulation rate, carbon geochemistry and clay mineralogy of ODP Site 181-1123 sediments, southwest Pacific

Site 1123 is located on the northeastern flank of the Chatham Rise. Sedimentological and clay mineralogical analyses indicate a very fine grained carbonate-rich sediment. Smectite and illite are the main constituents of the clay mineral assemblage. High smectite values in the Eocene decrease in younger sediment sequences. Illite and chlorite concentrations increase in younger sediments with significant steps at 13.5, 9, and 6.4 Ma. The kaolinite content is near the detection limit and not significant. We observed only small fluctuations of the clay mineral composition, which indicates a uniform sedimentation process, probably driven by long-term processes. Good correspondence is shown between increasing illite and chlorite values and the tectonic uplift history of the Southern Alps.

Data on multidisciplinary research in the Tajura Rift (Gulf of Aden) during Cruise 7 of R/V Akademik Mstislav Keldysh in winter 1983-1984

In the collective monograph results of geological and geophysical studies in the Tadjura Rift carried out by conventional outboard instruments and from deep/sea manned submersibles "Pisces" in winter 1983-1984 are reported. Main features of rift tectonics, geology, petrology, and geochemistry of basalts from the rift are under consideration. An emphasis is made on lithology, stratigraphy, and geochemistry of bottom sediments. Roles of terrigenous, edafogenic, biogenic, and hydrothermal components in formation of bottom sediments from the rift zone are shown.

Radiocarbon ages of bottom sediments and sedimentation rates in depressions of the Red Sea rift zone

Sedimentation rates (SR) for metalliferous and ore sediments containing ore material in 15 depressions of the Red Sea rift zone are discussed. SR for normal sediments was ca. 3.2 cm/ka in the second half of Holocene, 14.3 cm/ka yrs in the first half of Holocene, and 21.3 cm/ka in Late Würmian. Accumulation of metalliferous and ore sediments requires considerable accumulation of hydrothermal matter. Ore sediments have been found primarily in the Atlantis II and Chain Deeps; average sedimentation rate in these depressions is 90.0 cm/ka. In other depressions geothermal activity during considered time intervals was lower, and ore material occurs as admixture or in layers.

Stable isotope record, opal accumulation rate and geochemistry of middle Miocene sediments of IODP Site 321-U1338

During the middle Miocene, Earth's climate transitioned from a relatively warm phase (Miocene climatic optimum) into a colder mode with re-establishment of permanent ice sheets on Antarctica, thus marking a fundamental step in Cenozoic cooling. Carbon sequestration and atmospheric CO2 drawdown through increased terrestrial and/or marine productivity have been proposed as the main drivers of this fundamental transition. We integrate high-resolution (1-3 k.y.) benthic stable isotope data with XRF-scanner derived biogenic silica and carbonate accumulation estimates in an exceptionally well-preserved sedimentary archive, recovered at Integrated Ocean Drilling Program Site U1338, to reconstruct eastern equatorial Pacific productivity variations and to investigate temporal linkages between high- and low-latitude climate change over the interval 16-13 Ma. Our records show that the climatic optimum (16.8-14.7 Ma) was characterized by high amplitude climate variations, marked by intense perturbations of the carbon cycle. Episodes of peak warmth at (southern hemisphere) insolation maxima coincided with transient shoaling of the carbonate compensation depth and enhanced carbonate dissolution in the deep ocean. A switch to obliquity-paced climate variability after 14.7 Ma concurred with a general improvement in carbonate preservation and the onset of stepwise global cooling, culminating with extensive ice growth over Antarctica at ~13.8 Ma. We find that two massive increases in opal accumulation at ~14.0 and ~13.8 Ma occurred just before and during the final and most prominent cooling step, supporting the hypothesis that enhanced siliceous productivity in the eastern equatorial Pacific contributed to CO2 drawdown.

Radiocarbon sediment ages and sedimentation rates in the Red Sea

Results of radiocarbon dating of 23 cores (81 determinations) collected in the Red Sea rift zone at 8°N are presented. All of the main tectonic structures were dated: the upper and lower tectonic benches, the salt scarp, and the axial zone. Sediments in the upper tectonic bench exhibit normal sedimentation, while all other structures, which have highly dissected relief, show extensive re-deposition or non-accumulation of sediments. Sedimentation rate in Holocene was from two to three times lower than in Late Würm.

Seawater carbonate chemistry, nutrients, growth rate and phytoplnkton community response to increasing CO2 concentration during experiments, 2011

This paper reports for the first time upon the effects of increasing CO2 concentrations on a natural phytoplankton assemblage in a tropical estuary (the Godavari River Estuary in India). Two short-term (5-day) bottle experiments were conducted (with and without nutrient addition) during the pre-monsoon season when the partial pressure of CO2 in the surface water is quite low. The results reveal that the concentrations of total chlorophyll, the phytoplankton growth rate, the concentrations of particulate organic matter, the photosynthetic oxygen evolution rates, and the total bacterial count were higher under elevated CO2 treatments, as compared to ambient conditions (control). delta13C of particulate organic matter (POM) varied inversely with respect to CO2, indicating a clear signature of higher CO2 influx under the elevated CO2 levels. Whereas, delta13CPOM in the controls indicated the existence of an active bicarbonate transport system under limited CO2 supply. A considerable change in phytoplankton community structure was noticed, with marker pigment analysis by HPLC revealing that cyanobacteria were dominant over diatoms as CO2 concentrations increased. A mass balance calculation indicated that insufficient nutrients (N, P and Si) might have inhibited diatomgrowth compared to cyanobacteria, regardless of increased CO2 supply. The present study suggests that CO2 concentration and nutrient supply could have significant effects on phytoplankton physiology and community composition for natural phytoplankton communities in this region. However, this work was conducted during a non-discharge period (nutrient-limited conditions) and the responses of phytoplankton to increasing CO2 might not necessarily be the same during other seasons with high physicochemical variability. Further investigation is therefore needed.