scholarly journals Varying responses to I ndian monsoons during the past 220 kyr recorded in deep‐sea sediments in inner and outer regions of the G ulf of A den

2015 ◽  
Vol 120 (11) ◽  
pp. 7253-7270 ◽  
Author(s):  
Yuta Isaji ◽  
Hodaka Kawahata ◽  
Naohiko Ohkouchi ◽  
Nanako O. Ogawa ◽  
Masafumi Murayama ◽  
...  
Keyword(s):  
Deep Sea ◽  
The Past ◽  
Deep Sea Sediments

Pleistocene Climates in Central Europe: At least 17 Interglacials after the Olduvai Event

1977 ◽  
Vol 7 (3) ◽  
pp. 363-371 ◽  
Author(s):  
Julius Fink ◽  
George J. Kukla
Keyword(s):  
Environmental Change ◽  
Central Europe ◽  
Forest Soils ◽  
Deep Sea ◽  
Temperate Forests ◽  
Hardwood Forests ◽  
The Past ◽  
Deep Sea Sediments ◽  
Depositional Cycles ◽  
Definition Of

At least 17 times during the past 1.7 million years, the deposition of loess containing characteristic cold-resistant gastropods was interrupted by the development of temperate interglacial forests. This conclusion was reached in a study of paleomagnetically dated fossiliferous loess sequences in Krems, Austria and Brno, Czechoslovakia. Sequences of windblown loess interlayered with hillwash loams and steppe and forest soils exposed in brickyards around Brno and Praha, Czechoslovakia, revealed eight major depositional cycles within the Brunhes paleomagnetic epoch. We now report nine additional cycles of late and middle Matuyama age bringing the total number of glacial-interglacial cycles to 17, which occurred after the end of the Olduvai. The cycles are separated by marklines, levels of abrupt environmental change correlative with the terminations in deep-sea sediments. They are the boundaries between the windblown loess containing cold-resistant snail assemblages and between the clayey originally decalcified soils, accompanied by warmth loving Helix and Banatica snail faunas of hardwood forests. Because the presence of temperate forests in northwestern and central Europe is instrumental in the definition of an interglacial, each markline represents a glacial-interglacial boundary and each cycle is a glacial-interglacial cycle.

scholarly journals Changes in Ocean Ventilation Rates Over the Last 7000 Years Based on 14C Variations in the Atmosphere and Oceans

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 481-492 ◽  
Author(s):  
T-H Peng
Keyword(s):  
Age Differences ◽  
Benthic Foraminifera ◽  
Deep Sea ◽  
Ventilation Rate ◽  
Global Ocean ◽  
Production Rates ◽  
The Past ◽  
Ocean Ventilation ◽  
Deep Sea Sediments ◽  
Ventilation Rates

Changes in the ocean ventilation rate may be one of the causes for a net decrease of 100‰ Δ 14C in atmospheric CO2 over the last 8000 years. Ocean ventilation rates of the past can be derived from the 14C record preserved in planktonic and benthic foraminifera in deep-sea sediments. Results of 14C dating using accelerator mass spectrometry on deep sea sediments from the South China Sea show that the age differences between planktonic (G sacculifer) and benthic foraminifera increase from 1350 yr ca 7000 yr ago to 1590 yr at present. An 11-box geochemical model of global ocean circulation was used for this study. Both tree-ring-determined atmospheric 14C values and foraminifera 14C age differences are used as constraints to place limits on patterns of changes in ocean ventilation rates and in atmospheric 14C production rates. Results indicate: 1) 14C production rates in the atmosphere may have decreased by as much as 30% between 7000 and 3000 yr ago, and may have increased again by ca 15% in the past 2000 yr, and 2) the global ocean ventilation rate may not have been at steady state over the last 7000 yr, but may have slowed by as much as 35%.

scholarly journals Tephrostratigraphy of Deep-sea Sediments in the Northwestern Pacific and Its Implications for the Chronology of the Past 300kyr

2006 ◽  
Vol 45 (6) ◽  
pp. 435-450 ◽  
Author(s):  
Yusuke Suganuma ◽  
Kaori Aoki ◽  
Toshiya Kanamatsu ◽  
Toshitsugu Yamazaki
Keyword(s):  
Deep Sea ◽  
Northwestern Pacific ◽  
The Past ◽  
Deep Sea Sediments

scholarly journals Mechanism and Influencing Factors of REY Enrichment in Deep-Sea Sediments

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 196
Author(s):  
Jiangbo Ren ◽  
Yan Liu ◽  
Fenlian Wang ◽  
Gaowen He ◽  
Xiguang Deng ◽  
...  
Keyword(s):  
Deep Sea ◽  
Research Progress ◽  
Bottom Current ◽  
Knowledge Map ◽  
P2o5 Content ◽  
Deep Sea Sediments ◽  
Potential Resource ◽  
And Migration ◽  
Adsorption Desorption ◽  
Sediment Interface

Deep-sea sediments with high contents of rare-earth elements and yttrium (REY) are expected to serve as a potential resource for REY, which have recently been proved to be mainly contributed by phosphate component. Studies have shown that the carriers of REY in deep-sea sediments include aluminosilicate, Fe-Mn oxyhydroxides, and phosphate components. The ∑REY of the phosphate component is 1–2 orders of magnitude higher than those of the other two carriers, expressed as ∑REY = 0.001 × [Al2O3] − 0.002 × [MnO] + 0.056 × [P2O5] − 32. The sediment P2O5 content of 1.5% explains 89.1% of the total variance of the sediment ∑REY content. According to global data, P has a stronger positive correlation with ∑REY compared with Mn, Fe, Al, etc.; 45.5% of samples have a P2O5 content of less than 0.25%, and ∑REY of not higher than 400 ppm. The ∑REY of the phosphate component reaches n × 104 ppm, much higher than that of marine phosphorites and lower than that of REY-phosphate minerals, which are called REY-rich phosphates in this study. The results of microscopic observation and separation by grain size indicate that the REY-rich phosphate component is mainly composed of bioapatite. When ∑REY > 2000 ppm, the average CaO/P2O5 ratio of the samples is 1.55, indicating that the phosphate composition is between carbonate fluoroapatite and hydroxyfluorapatite. According to a knowledge map of sediment elements, the phosphate component is mainly composed of P, Ca, Sr, REY, Sc, U, and Th, and its chemical composition is relatively stable. The phosphate component has a negative Ce anomaly and positive Y anomaly, and a REY pattern similar to that of marine phosphorites and seawater. After the early diagenesis process (biogeochemistry, adsorption, desorption, transformation, and migration), the REY enrichment in the phosphate component is completed near the seawater/sediment interface. In the process of REY enrichment, the precipitation and enrichment of P is critical. According to current research progress, the REY enrichment is the result of comprehensive factors, including low sedimentation rate, high ∑REY of the bottom seawater, a non-carbonate depositional environment, oxidation conditions, and certain bottom current conditions.

The degradation activities for three seaweed polysaccharides of Shewanella sp. WPAGA9 isolated from deep‐sea sediments

2021 ◽  
Author(s):  
Dingquan Wang ◽  
Jianxin Wang ◽  
Runying Zeng ◽  
Jie Wu ◽  
Shijia V. Michael ◽  
...  
Keyword(s):  
Deep Sea ◽  
Deep Sea Sediments
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