Semi-automatic, autocorrelation-based varve counting and sediment chronology: the open source countMYvarves toolbox

Determining the chronology of sedimentary sequences is crucial to the study of paleoclimate, past volcanism, cryospheric change and more. Annual periodicity sediment layers, known as varves, can provide continuous and high-resolution chronologies of sedimentary sequences. Varve counting has a more than 100 year history and is not burdened with the high laboratory costs of many geochronological analyses. However, manual varve counts are time consuming, error prone, and can be subjective or challenging to reproduce. Several partially and fully automated numerical varve counting tools have been created to overcome these limitations. These are based on two main strategies: i) counting peaks or inflection points along a transect of digital varve image colour-intensity, and ii) machine learning techniques in which the computer is trained to identify varve boundaries. However, existing tools present limitations for semi-automated counting of complex or very fine scale varves.