Marine sedimentary record

The failure to identify the necessary authigenic silicate phases in sufficient quantities in marine sediments has led oceanographers to consider different approaches. The current models for seawater composition emphasize the dominant role played by the balance between the various inputs and outputs from the ocean. Mass balance calculations have become more important than solubility relationships in explaining oceanic chemistry. The difference between the equilibrium and mass balance points of view is not just a matter of mathematical and chemical formalism. In the equilibrium case, one would expect a very constant composition of the ocean and its sediments over geological time. In the other case, historical variations in the rates of input and removal should be reflected by changes in ocean composition and may be preserved in the sedimentary record. Models that emphasize the role of kinetic and material balance considerations are called kinetic models of seawater. This reasoning was pulled together by Broecker (1971) in a paper called "A kinetic model for the chemical composition of sea water."... 

The unique chemical composition of cosmogenous debris has provided some insight into why approximately 70% of the species of organisms on Earth were driven extinct over a relatively short time interval approximately 66 million years ago. Evidence for this mass extinction has been observed in marine sediments throughout all the ocean basins. In a contemporaneous layer deposited at the end of the Cretaceous period, the hard parts of many species of marine plankton abruptly vanished from the sedimentary record. This sedimentary layer is also characterized by a large enrichment in the rare element iridium. 

Follmi K. B. (1995b) A 160 m.y. record of marine sedimentary phosphorus burial coupling of climate and continental weathering under greenhouse and icehouse conditions. Geology 23, 859-862. 

Anderson, R.F., Lyons, T.W. and Cowie, G.L. (1994) Sedimentary record of a shoaling of the oxic/ anoxic interface in the Black Sea. Marine Geology, 116, 373-384. 

A number of factors are thought to influence the transformation of living coccolithophores from the surface ocean into the sedimentary record, many of which have an important bearing on the fossil record (see review by Baumaim et al. 2005). These include incorporation into fast sinking marine snow , breakage and dissolution due to grazing. 

FUtterer D. K. (1983) The modem upwelling record off Northwest Africa. In Coastal UpweUing. Its sediment record Part B Sedimentary records cf ancient coastal upwelling (eds. J. Thiede and E. SuEss), NATO Conference Series, Series IV Marine Science 10b, pp. 105-121. Plenum Press, New York. 

The concept for a marine paleoredox proxy based on variations in the U isotope ratio in sediments is very similar to the Mo isotope paleoredox proxy described earlier in this chapter. Since incorporation of U in oxidizing sediments such as ferromanganese crusts results in preferential removal of isotopically light U, and incorporation of U in reducing sediments results in preferential removal of isotopically heavy U, changes in the relative proportions of these two sinks over time should drive systematic shifts in the isotopic composition of U in seawater. In turn, these temporal shifts in the isotopic composition of seawater should be manifested as vertical fluctuations in in the sedimentary record. Excursions in the sedimentary record towards lighter values of (in any of these... 

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