We will enhance the modeling code so that it will perform the sectioning procedure automatically 

 and thus greatly reduce the amount of time needed to analyze complex data profiles. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



This computer modeling project requires no independent field collection activities. The 

 data to be used in this project will be provided through collaborations with other researchers in 

 the OMP, principally, Dr.'s L.K. Benninger and P. H. Santschi. However, as previously 

 mentioned, the determination of sediment ages from sediment core radionuclide profiles collected 

 during the initial field studies will be used to direct where additional resources should be 

 distributed. Sediment core sampling locations and sampling intervals will be defined to achieve 

 the desired level of detail in the analysis of carbon burial histories. 



METHODS AND PLATFORMS 



Natural excess 210 Pb and weapons-fallout nuclides ( 239,240 Pu, 137 Cs) provide information on 

 rates of sediment accumulation and mixing for the past 100 years. 14 C is used to determine 

 accumulation rates over longer time-scales. The numerical algorithm will be used to derive 

 accumulation rates from different tracer profiles to determine time variation in accumulation rates 

 in sediment cores from shelf -rise environments off Cape Hatteras. 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



Strengths - This new procedure is a vast improvement over conventional approaches for 

 determining sediment ages because it increases the number of data types from which realistic 

 sediment ages can be derived. Also, the resolution of the depth distribution of sediment ages is 

 significantly increased and the accuracy of these ages are well characterized. These improvements 

 will allow the OMP to use information collected early on in the field investigations to determine 

 where additional data is needed to achieve the desired spatial and temporal resolution. In 

 addition, data collected during previous investigations on sediment accumulation rates in the 

 MAB can be re-interpreted using the new procedure so that none of the historical investigations 

 need be repeated. 



Limitations - Tests conducted on synthetic profiles suggest that the procedure works best when 

 sediment accumulation rates are variable (Carroll et al., in prep.). If the evidence suggests that 

 sediment accumulation rates are constant at a location, we will apply both the new and 

 conventional procedures. 



In all cases, it is important to identify historical markers in the sediments, such as 239240 Pu 

 and 137 Cs, to improve the accuracy of the sediment age determinations. When a marker is not 



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