available, the sediment age probability distribution functions are broad and thus the ages are 

 poorly constrained. 



It is important to recognize that the resolution of sediment age determinations will 

 depend on the sampling interval chosen for the sediment cores. In environments where the 

 magnitude and frequency of sediment accumulation rate changes is high, the number of sediment 

 core sampling intervals must be increased accordingly. The frequency of changing sediment 

 accumulation rates that can be resolved will be determined by the number of data points for each 

 radionuclide profile and is defined by the Nyquist sampling frequency. 



STATUS OF RESEARCH 



For the previous two years, we have performed numerous tests to determine the strengths 

 and limitations of this modeling procedure and have significantly improved the numerical 

 algorithms used in the procedure. The numerical code has been completely re-written from the 

 programming language "Fortran" into "C". During this transition, several errors in the code were 

 identified and corrected. In addition many of the fundamental numerical analysis routines were 

 improved. Paramount among these improvements was the development of a new convergence 

 routine that considers the uncertainty associated with each data point in finding the optimum set 

 of ages at each sediment depth (Carroll et al., submitted (a)). 



Numerous synthetic data profiles with known sediment accumulation rates have been 

 analyzed using the procedure (Carroll et al., submitted (a)) These tests have provided essential 

 information on the kinds of radioisotope profiles that the procedure will assign with correct 

 sediment ages. Historical data on radionuclide profiles from sediment cores collected from a 

 variety of environments have also been analyzed (Carroll et. al., submitted (b)). While we 

 continue improving the modeling procedure we are beginning to place more emphasis on locating 

 and re-analyzing data that is currently available from previous investigations in the MAB region. 



Keywords: sediment accumulation, sediment mixing, sediment ages, isotopes 



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