Effect of bioturbation on concentration profiles in sediments

The simplest approach considers a perfectly mixed bioturbated layer of thickness L and homogeneous concentration C. If v is the sedimentation rate, the mass balance condition for element i reads 

Fora bioturbation of constant thickness L, the conservation equation now becomes 

Michel et al. (1990) have measured the iridium content in Ocean Drilling Project hole 690 sediments from the Weddel Sea across the Cretaceous-Tertiary (K-T) boundary (Table 8.1). Depth z is relative to an arbitrary level in the core. Compare the reduced iridium flux at each depth down the core assuming the bioturbated layer is either 4 or 8 cm thick. 

Making the approximation at the fcth depth level that 

Depth z (cm) is measured relative to an arbitrary reference layer. 

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