Detrital zircon dating

07-Nov-2020 12:50

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We demonstrate that statistically significant differences amongst detrital zircon samples derived from the same (integrated) source region can be introduced by the dynamics of sediment transport, which may in turn lead to erroneous geologic interpretations arising from the inaccurate assumptions that, at present, condition the quantitative treatment of detrital zircon data.“The fascinating impressiveness of rigorous mathematical analysis, with its atmosphere of precision and elegance, should not blind us to the defects of the premises that condition the whole process.”—Thomas C. Most sediment provenance studies that apply quantitative detrital zircon U-Pb geochronology rely on the assumption that direct intersample comparisons using dissimilarity metrics allows for determination of similar and/or distinct sediment sources (e.g., Saylor and Sundell, 2016; Vermeesch, 2018, and references therein).

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But do they recognize all the possible sources of error? To determine the provenance of sediments, geologists are often tasked with making geological interpretations based on comparison of samples collected tens to thousands of kilometers apart, sometimes across terrane boundaries and modern or ancient ocean basins (e.g., Rainbird et al., 1992).

What we want to ask, now that this paper has shown a significant “unknown” in geological sample collection and testing, is what other unknowns are still out there? Do any of them really know how old their samples are?

Subduction along the southern margin of Alaska, USA, has been ongoing since at least the Jurassic.

Here we use a double-dating approach that combines fission track dating and U-Pb dating on individual detrital zircon grains.

In total we analyzed more than 1700 zircons from Eocene to Pliocene strata and modern river sand that has eroded from the surrounding regions of the Cook Inlet basin.However, the character of the subducting slab has changed through time and has included subduction of normal oceanic crust, a spreading ridge, and an oceanic plateau.