Late Quaternary Sediment of the Panama Basin: Sedimentation Rates, Periodicities, and Controls of Carbonate and Opal Accumulation

Assuming a constant rate of quartz accumulation for deep-sea sediment core Y69-106P, from the Panama Basin, I have estimated the age of samples from the core and have constructed a curve for sedimentation-rate versus time. Strati-graphic controls for the calculated time scale include three C14 measurements, the extinction of the radiolarian Stylatractus universus, correlation with oxygen-isotope curves from other dated cores, and an Ar 4 0 /Ar 3 9 age determination. The model sedimentation rates, when combined with data on mineralogic composi-tion, allow the determination of accumulation rates for CaC0 3, opaline Si0 2, and remaining "detr i tus. " Fluctuations in CaC0 3 accumulation rates over time correlate with variations in oxygen-isotope ratios in biogenous carbonate from two other equatorial Pacific cores; high oxygen-isotope ratios correlate with high C a C 0 3 accumulation rates. Opaline S i0 2 accumulation rates reflect changes in the dominance of different radiolarian fossil groups, changes which can be related to surface circulation in the Panama Basin. Spectral analysis of the accumulation rate of CaC0 3 in core Y69-106P and of the oxygen-isotope record of core V28-238 indicates a 23,000-yr periodicity. Spectral analysis of the opal accumulation rate suggests a 100,000-yr periodicity, which is an important frequency in the oxygen-isotope record. Both these periodicities are close to those found in fluctuations in the Earth's orbital parameters. The eccentricity of the orbit fluctuates with an average period of 98,000 yr, and the precession of the equinoxes changes with a period of 22,000 yr