Developing a statistical approach to analyze large paired geo-thermochronological datasets with an application to the Canadian Cordilleras

• Applicant: Dr. Tobias Stephan
• Subject Area: Palaeontology
• Term: from 2020 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 439621066

Laser ablation U–Pb dating of detrital minerals is the most common approach in provenance analyses. The method allows producing large geochronological datasets in a fast and cost efficient manner as wells as the application of several different dating methods such as U–Pb, (U–Th)/He, and fission track on the same detrital grain. The combination of geochronological and thermochronological methods provides valuable information for the understanding the coupling between tectonic processes, erosion, sedimentary transport and recycling, and paleo-climate.The increase of age data complicates the data analysis and thus the interpretation. The combination of several different provenance information, in particular the use of multi-method ages from single grains, expands the dataset by one or more dimensions. The multivariate analysis of more than one provenance proxy is complex and mostly done by analyzing the individual proxies separately. This approach, however, does not exhaust the entire potential of multi-method provenance analysis as it ignores the initial linkage of the different information of each individual grain and, thus, erroneously assumes that the different information represent independent variables. The overarching objective of this project is to develop a statistical procedure for quantitative provenance analysis using a large amount of samples analyzed by multi-method dating. By applying modern statistical methods such as Bayesian inference, dimensionality reduction and clustering, the procedure will include quantification of the dissimilarities of the samples, identification of the provenance endmember, quantification of sedimentary mixing, and prediction of provenance of single-method age datasets. In order to guarantee geological meaningful results, a priori assumptions on the multi-method dataset have to be made in the first place. This step will include data pre-processing, bias, and noise reduction. The numeric quantification of the pairwise dissimilarities of multi-method dated detrital sample will be pursued by testing two approaches: (i) non-negative matrix factorization and (ii) trans-dimensional Bayesian mixture modelling applying hierarchical models for noise estimation. Provenance endmember and sedimentary mixing will be identified and quantified by exploratory data analysis, in particular multidimensional scaling and density-based clustering. The statistic procedure will be tested on synthetically generated datasets and double- and triple dated detritus from the Canadian Cordilleras.The new approach can be easily applied to other paired radio-isotopic chronometers, e.g. U–Pb and Lu–Hf dating, which offers a large potential for future geo- and thermochronological studies. Moreover, it will provide robust results for quantitative provenance analysis that are required to understand the complex coupling between endogenous and exogenous processes.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professorin Dr. Eva Enkelmann