Investigation of Dating Techniques

Berillium-10 is frequently used as a dating technique in comparison of the ratio to Aluminimum-26. The two nuclides pairs is used because of the difference in half-life between the two, as 26-Al has a half like of 0.7 Ma compared to 10-Be's 1.4 Ma. Although this is a common method, it is not very successful for dating sediment outside that age range. For this research, they instead use Chlorine-36 and Berillium-10, which offers a much more precise burial age because this pair has a smaller half-life ratio of 0.38 Ma compared to 1.43 Ma. With that being said, Cl-36 and Be-10 do not typically occur in the same mineral as Al and Be do in quartz; however, this research finds that the production rates of Cl in potassium feldspars are similar to that of Be in quartz. Using samples of granitoid cobbles containing both feldspars and quartz in the Mission Creek area of the San Andreas Fault, they hoped to determine the age of the alluvial sediment as well as determine the origin, to analyze the movement of the fault slip over time. Corrections had to be made for Radiogenic Cl because the decay U and Th in rocks produces thermal neutrons that are captured in the 10-Cl reaction. With these considerations, they found that their data on loose clasts were less precise, but their calculations and assumptions of steady erosion for bedrock sample were consistent. This research is helpful for future research, informing the effective applications of ratio of 36-Cl/10-Be dating technique.

In Southern Norway, samples from boulders in a variety of locations were taken in order to reconstruct the thickness of the Fennoscandian Ice Sheet since the last glacial maximum (LGM). The sample were from boulder erratics on glacial till, bedrock, and fractured rock from the original bedrock material. This investigation assumes that the erosion since the LGM has been a minimal impact on overall results, however, the research does take in to consideration of the erosional history of the underlying surface. The research entailed the collection of samples and inference of which boulders were likely to be true glacial erratics and the documentation of the exact location of where the sample was taken from. The samples were then taken to a lab and processed. The data was reevaluted with the consideration of isostatic rebound/depression, as well as the seasonal weather patterns. Although, this method required some inferences and assumption, the conluding results offer an insightful look at the patterns of the retreat of the Fennoscandian Ice Sheet in relation to time and space.