Sediment diatom records

Most commercial marine diatomite deposits exploit accumulations resulting from large blooms of diatoms that occurred ia the oceans during the Miocene geological epoch. Diatomite sediments older than the Jurassic period are rare in the fossil record. Commercial deposits of diatomite are accumulations of the fossil skeletons, which can occur in beds as thick as 900 m in some locations (5). Marine deposits must have been formed on the bottom of protected basins or other bodies of quiet water, undisturbed by strong currents, in an environment similar to the existing Santa Barbara Channel or Gulf of California (3,6). 

Water column biogeochemical processes, however, do not always leave an obvious record in the seabed. For example, Amazon shelf sediments have little biogenic silica accumulation despite extensive diatom production and abundance in estuarine surface... 

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]. 

Figure 12. Sedimentary and geochemical records from oceans, showing dramatic transient shifts in most records in an interval from just before 8 Ma to 4 Ma (shaded), from Filippelli (1997b). Symbols in all records represent averages of 1 Myr intervals, except for normalized sediment flux curve, which represents 0.5 Myr averages. After interval averaging, all records were adjusted to time scale of Cande and Kent (1992) for consistency, (a) Normalized sediment flux in northern Indian Ocean (Rea 1992). (b) Ge/Si ratio in opaline silica from diatoms (Shemesh et al. 1989). (c) of bulk marine carbonates (Shackleton 1987). Although details of different carbon isotope records differ, general trends revealed in this low-resolution record are robust. PDB is Pee Dee belemnite. (d) Phosphorus accumulation rates in equatorial Pacific (Filippelli and Delaney 1994). Peak in accumulation rates is also observed in other parts of Pacific (Moody et al. 1988) and western Atlantic (Delaney and Anderson 1997). These peaks are linked with increased phosphorus input rates from continental weathering (e.g., Filippelli and Delaney 1994). (e) Sr/ Sr record from marine carbonates (Hodell et al. 1990, 1991). (f) of benthic foraminifera (Miller et al 1987).

Element concentration data are ideal as qualitative evidence for atmospheric contamination. However, it is desirable that lake sediment records can give quantitative estimates of loadings over time. Mackereth (1966) recognized that trace elements were supplied in labile form to the lake, and therefore their concentration in the sediment reflected capture efficiency as much as supply. Hamilton-Taylor (1979) echoed this concern, suggesting that in Windermere the metal concentrations a) might be controlled by diatom flux and b) might be low due to outflow loss. The model outlined in the section Models Unking flux and concentration can be used to estimate atmospheric fluxes from sediment concentration data (also, see Boyle Birks, 1999). 

Ochsenbein, U., W. Davison, J. Hilton E. Y. Haworth, 1983. The geochemical record of major cations and trace metals in a productive lake — analysis of thinly sliced sediment samples characterised by diatom stratigraphy. Arch. Hydrobiol. 98 463-488. 

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