Oceans sediment core

Fontugne M. R. and Duplessy J.-C. (1986) Variations of the monsoon regime during the upper Quaternary evidence from carbon isotopic record of organic matter in North Indian Ocean sediment cores. Palaeogeogr. Paleoclimatol. Palaeoecol. 56, 69-88. 

Figure 7. (a) Vostok ice core CO2 record reported as ppmv (part per million by volumbe) (9). (b) Ocean sediment core (G. ruber, a species of foraminifera) oxygen isotope record reported as the deviation in parts per thousand from the marine carbonate standard V-PDB (both sea-surface temperature and changes in the bulk seawater oxygen isotope composition affect this record) (49), and boron isotope based pH values reported relative to the seawater pH scale (large squares) (50). (c). Continental ice volume signal from seawater reported... 

The advent of new techniques to collect undisturbed sediment cores, with well preserved sediment - water interface has brought into sharper focus the various deep sea sedimentary processes, their rates and their effects on the preserved records. As mentioned earlier, recent studies have shown that the record contained in sediments is not a direct reflection of the delivery pattern of a substance to the ocean floor as has so far been assumed the record is modified as a result of several complex physical, chemical and biological processes. Therefore, information on the temporal variations in the tracer input to oceans, if sought, has to be deciphered from the sediment-residuum. In the following we consider one specific example of retrieval of information from the sediment pile the application of deep sea sediments to obtain historical records of cosmic ray intensity variations. 

The presence of organic compounds in river and oceanic sediments is due, in part, to manmade pollution and monitoring the levels of these substances in the sediment and sediment cores provides an indication of the time dependence of their concentration over large time spans. Contamination of sediments is found not only in rivers but also in estuarine and oceanic sediments and thus sediment analysis provides a means of tracking organic from their source through the ecosystem. 

In ocean drilling, hydrated sediment cores are often obtained. Because the cores frequently traverse warm waters for periods of about 1 h, hydrated cores dissociate and release gas, to yield higher pressures. When core liners are retrieved on the deck of a drilling vessel, frequently the warm weather can cause additional hydrate dissolution, resulting in further pressure increases. The modeling of this dissociation has been done by Wright et al. (2005) and by Davies et al. (2006). 

Much of what is currently known about the Earth s climate comes from the application of stable isotopes collected from ocean drill cores in marine sediments (e.g., Zachos et al. 2001). These isotopic data sets provide detailed records of how the Earth s oceans have responded to changing climate and are extremely valuable in assessing global climate histories down to millennial scales. Similar detailed isotopic records for terrestrial systems are, however, uncommon and frequently continuous terrestrial climate records that span millions to tens of millions of years are not preserved in the terrestrial geologic record. With the advent of paleoaltimetry studies targeted directly at the coupled isotopic effects of changes in climate... 

As mentioned above, a given sediment core will simultaneously provide information on at least three separate quantities changes in mean ocean nitrate changes in... 

Masiello and Druffel (1998) measured the abundance and radiocarbon content of BC (isolated by wet chemical oxidation) in sediment cores from two deep Pacific Ocean sites. They found BC comprises 12-31% of the total sedimentary OC, and was between 2,400 yr and 13,000 yr older than non-BC sedimentary OC (Figure 5). For sediment intervals deposited prior to the Industrial era (i.e., free of BC inputs from fossil fuel utilization), the authors argue that the older ages for BC must be due to storage in an intermediate reservoir before deposition. Possible intermediate pools are oceanic DOC and terrestrial soils. They conclude that if DOC is the intermediate reservoir, then BC comprises 4-22% of the DOC pool. If soils are the intermediate reservoir, then the importance of riverine OC has been underestimated. 

The more recent work with °Th and Pa has been concerned less with their use to establish absolute chronology and more with the interpretation of their profiles in sediment cores to determine shorter-term variability in particle flux. Particle-flux measurements with sediment traps and other studies of the behavior of °Th and Pa in the oceanic water column have resulted in a better understanding of the extent to which they can be laterally redistributed following their production. It has been shown that, over much of the ocean, the redistribution of °Th is minimal, so... 

Figure 10 LGM distribution of benthic foraminiferal and S 0 in sediment cores from the deep ocean (mostly >2,000 m water depth) (Duplessy et al, 2002). The very high and low in the Southern Ocean suggest a separate water mass from those filling the deep Atlantic and Pacific basins (Duplessey et al, 2002) (reproduced by permission of Elsevier from Quat. Sci.

Bismuth concentrations in marine sediment cores from Narragansett Bay (water depth, 8m) and Pacific Ocean (I) (35°31 N, 123° 19 W water depths, 4300m) and Pacific Ocean (II) (55°35 N. 169°23 W water depth, 1598 m) are shown in Table 15, which shows that the Narragansett Bay sediments contained higher bismuth concentrations than their North... 

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