Oceans inputs

Figure 3 Schematic cartoon depicting oceanic inputs and cycles of select U-Th series isotopes...

A box model fiar the marine silica cycle is presented in Figure 6.11 with respect to the processes that control DSi and BSi. An oceanic budget is provided in Table 16.3 in which site-specific contributions to oceanic outputs are given. This table illustrates that considerable uncertainty still exists in estimating the burial rate of BSi. Regardless, burial of BSi is responsible for most of the removal of the oceanic inputs of DSi, with the latter being predominantly delivered via river runoff. This demonstrates the importance of the biological silica pump in the crustal-ocean-atmosphere factory. 

Ludwig, W., J.-L. Probst, and S. Kempe. 1997. Predicting the oceanic input of organic carbon by continental erosion. Global Biogeochemical Cycles 10 23-41. 

Through the influence of speciation on oceanic input and removal processes it is expected that chemical form should strongly influence not only overall chemical concentrations in the ocean but also chemical distributions. In view of this expectation, assessments of speciation and comparative chemistries in this chapter are made in the context of vertical distributions (concentrations vs depth) of chemical species in the ocean. Since elemental distributions are influenced not... 

Figure 5 A cross-plot of Os/ Os versus Sr/ Sr illustrating the isotopic ratios associated with various oceanic inputs. Solid black arrows schematically illustrate the temporal evolution of seawater during the Cenozoic. Data sources (see Table 1 also) are (-) Cenozoic seawater (o) Loess deposits, Peucker-Ehrenbrink and Jahn (2001) (-I-) Indus paleosols, Chesley et al. (2000) and (x) Ganges paleosols, Chesley et al. (2000).

The input of Sr required to account for the observed enlrancement in Sr/ Sr ratio across the KTB can be determined by mass balance of the isotopes of Sr. Assuming the mid-ocean ridge (MOR) flux and isotopic ratio of Sr were unchanged, the total oceanic input of Sr at tlie KTB is described by the equation... 

Estimates of potential trace metal oceanic input based on atmospheric washout, mining productivity figures, and relative river transport are given in Tables 1 and 2. 

In this budget, both estimates for dissolved inorganic nitrogen (DIN) and silicon fluxes are included. The silicon budget is included as a control. The processes involved in the silicon cycle are fewer than that of nitrogen, and so it might be expected that the budget can be closed more easily. The silicon cycle comprises essentially only river and ocean inputs, removal of dissolved silicon... 

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