Evaluating the natural bias on the detrital record imparted by riverine systems

We analyze modern riverine sediments to evaluate if the detrital record may be (heavily!) biased by riverine systems. Turns out that the paleoenvironmental and tectonic reconstruction should be conducted with more care than previously thought!

 Summary

In this study we conduct a high-resolution and large-n detrital zircon study modern sediments from the Bermejo river, which comes out of the Subandean Andes and drains the Chaco Megafan before merging with the Paraguay river. Importantly, there are no tributaries for over ~1000 km that may alter o induce noise in the detrital signal, turning it in an excellen case study for evaluating how detrital zircon crystals may be affected during transport and if hydraulic sorting plays a significant role in the detrital record.

The approach to conduct these analysis was also developed for this study, where samples are first imaged using XRCT to reconstruct their morphological characteristics and then dated using U-Pb LA-ICP-MS data. Additionally, the degree of cristalinity of each zircon crystal, which may also play a significant role when determining their transport capacity, may be calculated after their Raman spectra.

Based on the results, we find that samples from within the same locality may yield different detrital spectra and that Kolgomorov-Smirnov test is not an approach that is robust enough to simply accept/reject pairs of the samples. In fact, multidimensional models may be required to better generate more robust models moving forward.