Sedimentary record change

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."... 

Montoya, J.P. (1994) Nitrogen isotope fractionation in the modern ocean implications for the sedimentary record. In Carbon Cycling in the Glacial Ocean Constraints on the Ocean s Role in Global Change (Zahn, R., Pedersen, T.F., Kaminski, M.A., and Labeyrie, L., eds.), pp. 259-280, Springe, Berlin. 

Lateral transport of particles is an important component of modern biogeochemical cycles. Furthermore, lateral redistribution of sediments modifies the sedimentary record of past changes in environmental conditions. Therefore, paleoceano-graphic studies that rely on reconstructing accumulation rates of sedimentary constituents must account for lateral redistribution of sediments within the ocean. 

Sedimentary Records of Environmental Changes and Anthropogenic Impacts during the Past Decades... 

SEDIMENTARY RECORDS OF ENVIRONMENTAL CHANGES AND ANTHROPOGENIC IMPACTS... 

In the case of freshwaters, the past effects of climate change on UV exposure have impacted sedimentary records in a remarkable way. Analysis of fossil diatom assemblages in Canadian subarctic lake sediments has provided evidence of the interactive impacts of climate change and solar UVR on CDOM concentrations during the Holocene [86]. 

The clearest sedimentary records of sea-level change occur where there is a good and steady supply of sediment and where the land is slowly and steadily sinking relative to mean sea level (Pitman,... 

Information about how long this process has been operating can be obtained from the sedimentary record. Loess, derived from source rocks that extend back almost 2 billion years, has uniform REE patterns. This indicates that during the period represented by the source regions of the loesses, the processes producing the upper crust have not changed. Thus the composition of the upper continental crust has been uniform and produced by similar processes well back into the Proterozoic. 

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