Flexible paleoclimate age-depth models using an autoregressive gamma process

TLDR

Radiocarbon dating is routinely used in paleoecology to build chronologies of lake and peat sediments, linking depth to age. The study introduces Bacon, a new chronology‑building approach that has attracted enthusiastic attention from paleoecologists. Bacon models core accumulation rates with a gamma autoregressive semiparametric process, incorporates informative priors, uses a robust adaptive t‑walk MCMC sampler, and handles outliers via a Student‑t radiocarbon model. In two case studies—a peat core and a lake core—Bacon’s results were compared with other methods, demonstrating its performance.

Abstract

Radiocarbon dating is routinely used in paleoecology to build chronologies of lake and peat sediments, aiming at inferring a model that would relate the sediment depth with its age. We present a new approach for chronology building (called "Bacon") that has received enthusiastic attention by paleoecologists. Our methodology is based on controlling core accumulation rates using a gamma autoregressive semiparametric model with an arbitrary number of subdivisions along the sediment. Using prior knowledge about accumulation rates is crucial and informative priors are routinely used. Since many sediment cores are currently analyzed, using different data sets and prior distributions, a robust (adaptive) MCMC is very useful. We use the t-walk (Christen and Fox, 2010), a self adjusting, robust MCMC sampling algorithm, that works acceptably well in many situations. Outliers are also addressed using a recent approach that considers a Student-t model for radiocarbon data. Two examples are presented here, that of a peat core and a core from a lake, and our results are compared with other approaches.