Maximum depositional age estimation revisited

In a recent review published in this journal, Coutts et al. (2019) compared nine different ways to estimate the maximum depositional age (MDA) of siliclastic rocks by means detrital geochronology. Their results show that among these methods three are positively and six negatively biased. This paper investigates the cause these biases proposes solution it. A simple toy example shows that it is theoretically impossible for the reviewed find correct even best case scenario: MDA estimates drift ever smaller values with increasing sample size. The issue can be solved using maximum likelihood model was originally developed fission track thermochronology Galbraith Laslett (1993). approach parameterises estimation problem binary mixture discrete continuous distributions. The ‘Maximum Likelihood Age’ (MLA) algorithm converges unique value, unlike ad hoc methods reviewed (2019). It successfully recovers example, produces sensible realistic illustrated an application dataset 13 sandstone samples were analysed both LA-ICPMS CA-TIMS U–Pb algorithms produce unrealistic systematically younger data than the CA-TIMS data. MLA does not suffer from negative bias. method purely statistical approach estimation. Like methods, readily accommodate geological complications such as post-depositional Pb-loss, or analytical issues causing erroneously young outliers. in such complex cases re-analyse youngest grains more accurate dating techniques. the MLA visualised on radial plots. Both plots have applications outside detrital geochronology, determine volcanic eruption ages.