UNRAVELING THE UNCERTAINTIES OF DETRITAL ZIRCON PROVENANCE ANALYSIS WITH JOINT LANDSCAPE AND PROVENANCE MODELLING: INSIGHTS INTO SEDIMENT DYNAMICS AND LANDSCAPE EVOLUTION

Environmental signals preserved in the depositional record reflect variations in the production of sediment, transport, or deposition caused by environmental disruptions. Those can be triggered by sea level changes, tectonics, human intervention, and climate, among other factors. A wide array of environmental signals exists, but a common target for analysis is sediment provenance and detrital zircon U-Pb geochronology. This method has swiftly progressed from a technology with an ostensibly limited utility to an almost essential technique for analyzing sedimentary units and their source areas. In concert with developments in analytical techniques, sophisticated methods have developed to interpret the results, for example, those for “unmixing” provenance samples to estimate contributions from different source terranes. Here we consider ways to account for sources of uncertainty related to specific assumptions made during unmixing and similar methods. To tease these uncertainties out, we model synthetic landscapes along with their expected provenance evolution. This allows us to isolate generative parameters, like spatially variable erosion, rock strength, and zircon fertility, to account for variable provenance at the outlet. Multiple statistical approaches can be combined to perform this task, accounting for the uncertainties involved in the sampling and analysis of source-to-sink systems. Our preliminary efforts involve a simplified beginning case, simulating an environment with two different sources with varying properties being exposed progressively in a setting with a main drainage divide between basins. Each source has a specific signature, and within the model environment, the produced sediment is mixed as it is routed and can be “sampled” anywhere in the network. Comparing suites of simulated results across a range of parameter space with those inferred from simple and common assumptions, e.g., same zircon fertility between units, constant erosion rate, etc., allows for an assessment of the potential uncertainty and the generative sources of that uncertainty in these analyses. The quantification of uncertainty within detrital zircon provenance analysis has the potential to provide insights into sediment dynamics and landscape evolution typically interpreted from these records.