Unraveling burial histories with CosmoChron

Cosmogenic nuclides measured in depth-profiles are a valuable tool for reconstructing the depositional and erosional history of sedimentary sequences. The burial ages of these sequences can be determined by measuring cosmogenic nuclide pairs such as ²⁶Al and ¹⁰Be. However, some conventional approaches neglect post-burial nuclide production, a major source of error.

A new model, CosmoChron (Sørensen et al., 2024, Quat. Geochron. 85, 101618), enables a more versatile and comprehensive analysis by integrating nuclide data with independent age constraints, such as OSL dating or magnetostratigraphy. CosmoChron employs probabilistic inverse modeling, incorporating prior information about accumulation processes and sample origins. The forward model accounts for ²⁶Al/¹⁰Be ratios, pre-burial conditions, radioactive decay, post-burial production, and unconformities, allowing for more precise reconstructions, including hiatuses at unconformities.

We demonstrate CosmoChron via two case studies: (1) a drill-core at Wapenveld (the Netherlands) penetrates the Early Pleistocene “Hattem” beds—thought to be among the earliest glacigenic deposits in Europe. The samples are from three distinct layers with several unconformities and a stratigraphic age constraint at the base. And (2) Fisher Valley (Utah, USA) contains samples from Early Pleistocene alluvial sediments with depth-profile burial ages published by Balco and Stone (2005, ESPL 30, 1051-1067). We recalculate the age-depth relationship, compare the methods, and explore the differences in the results.

We discuss the advantages and limitations of depth-profiles and CosmoChron, emphasizing its ability to provide detailed temporal reconstructions while requiring robust site-specific information.