Using seismic data to investigate how carbonate accumulation rates vary with depth

What is it about?

In early work on the deposition of pelagic carbonate sediments in the 1970s, it was suggested that carbonate dissolution begins strongly at a lysocline and completes at the carbonate compensation depth. In attempting to visualise this and analyze estimates of accumulation rates from DSDP drill cores, researchers assumed that accumulation rates decrease linearly with depth over this interval. We investigated this idea with two lines of seismic reflection data crossing the equatorial Pacific sediment bulge, using the thicknesses between regional reflections to map out the long term spatial patterns of accumulation rates between known age intervals. If the dissolution model were correct, the mass difference of these intervals between the two lines should also follow a linear trend with depth differences. We found no such relationship, arguing against the simple linear model.

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Why is it important?

Most work on long-term carbonate dissolution has used information from the scientific drilling cores. However, deposition rates at individual drill sites are subject to bias (sites are commonly located in areas of thicker sediment and hence preferential deposition). Seismic reflection data on the other hand, though lacking such fine age resolution as found in cores, do provide a way to overcome spatial variations in accumulation rates, thus a combined approach of using the two data types together may be better when quantifying depositional fluxes of various kinds.