Abstract
The majority of palaeoenvironmental information is inferred from proxy data contained in accretionary sediments, called geo-archives. The validity of proxy data and analysis workflows are usually assumed implicitly, with systematic tests and uncertainty estimates restricted to modern analogue studies or reduced-complexity case studies. However, a more generic and consistent approach to exploring the validity and variability of proxy functions would be to translate a given geo-archive into a model scenario: a "virtual twin". Here, we introduce a conceptual framework and numerical toolset that allows the definition and analysis of synthetic sediment sections. The R package sandbox describes arbitrary stratigraphically consistent deposits by depth-dependent rules and grain-specific parameters, allowing full scalability and flexibility. Virtual samples can be taken, resulting in discrete grain-mixtures with well-defined parameters. These samples can then be virtually prepared and analysed, for example to test hypotheses. We illustrate the concept of sandbox, explain how a sediment section can be mapped into the model and, by focusing on an exemplary field of application, we explore universal geochronological research questions related to the effects of sample geometry and grain-size specific age inheritance. We summarise further application scenarios of the model framework, relevant for but not restricted to the broader geochronological community.
Highlights
We illustrate the concept of sandbox, explain how a sediment section can be mapped into the model and, by focusing on an exemplary field of application, we explore universal geochronological research questions related to the effects of sample geometry and grain-size specific age inheritance
Artificial, peaks occurred below the main modes of the other end-members, as commonly encountered in end-member modelling analysis (EMMA) (Dietze and Dietze, 2019)
The proposed structure of sandbox, consisting of grains, populations, parameters, rules, and functions, allows to consistently define synthetic sections that can be used to pursue a series of research questions, for 405 instance the study of the effects of sampling container size and grain size related age inheritance on the expected age scatter
Summary
Information about the evolution of earth-surface dynamics beyond the timespan of instrumental records is predominantly gathered from sedimentological deposits, serving as hosts of proxy data. Proxies are based on the presupposition that a specific sediment property is representative of an unknown environmental variable or can be unequivocally converted into such. The grain-size distribution of a sample is supposed to reflect the sediment transport processes, the isotopic composition of fossils represents precipitation or temperature, charcoal occurrence indicates human activity within a landscape, or trapped charges in minerals denote a depositional age. The validity of proxies is usually an assumption based on conceptual relationships, modern analogue data, or physical principles.
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