Are global U-Pb detrital zircon age distributions valid proxies for global igneous activity?

When interpreting results, it is imperative to have some understanding of the degree to which the results are replicable. If the results cannot be replicated with independent data, then interpretations from the results become questionable. To minimize the potential for misinterpretations, the current study analyzes six time-series derived from globally sampled U-Pb zircon databases – of which, two are independent igneous databases, one being a quasi-independent igneous database, and three being independent detrital databases. These time-series are then analyzed with standard statistical methods to evaluate replicability. The methods include bandpass filtering to transform the raw time-series into stationary sequences, Student’s t-test, Monte Carlo simulations, periodograms from spectral analysis, correlation studies, and correlograms. Each test is designed to determine the replicability of a specific time-series, as well as the replicability of periodicities found from the time-series. The results show at least three key components to assessing replicability: (a) U-Pb igneous and detrital zircon age distributions are highly replicable, (b) time-series replicability gradually deteriorates with age, and (c) replicability is scale dependent, with low frequency cycles being more replicable than high frequency cycles. From the tests, we conclude that four harmonic cycles are highly replicable and statistically significant, these being periodicities of 810, 270, 90, and 67.5-myr.