META-ANALYSIS OF CRYOGENIAN THROUGH MODERN QUARTZ MICROTEXTURES REVEALS SEDIMENT TRANSPORT HISTORIES

Quantitative analysis of quartz microtextures by means of scanning electron microscopy (SEM) can reveal the transport histories of modern and ancient sediments. However, because workers identify and count microtextures differently, it is difficult to directly compare quantitative microtextural data analyzed by different workers. As a result, the defining microtextures of certain transport modes and their probabilities of occurrence are not well constrained. We used principal-component analysis (PCA) to directly compare modern and ancient aeolian, fluvial, and glacial samples from the literature with nine new samples from active aeolian and glacial environments. Our results demonstrate that PCA can group microtextural samples by transport mode and differentiate between aeolian transport and fluvial and glacial transport across studies. The PCA ordination indicates that aeolian samples are distinct from fluvial and glacial samples, which are in turn difficult to disambiguate from each other. Ancient and modern sediments are also shown to have quantitatively similar microtextural relationships. Therefore, PCA may be a useful tool to constrain the ambiguous transport histories of some ancient sediment grains. As a case study, we analyzed two samples with ambiguous transport histories from the Cryogenian Bravika Member (Svalbard). Integrating PCA with field observations, we find evidence that the Bravika Member facies investigated here includes aeolian deposition and may be analogous to syn-glacial Marinoan aeolian units including the Bakoye Formation in Mali and the Whyalla Sandstone in South Australia.

Automated summary

The study demonstrates that principal-component analysis (PCA) can effectively differentiate microtexture samples of different sediments, validate differences between aeolian transport and fluvial/glacial transport, and constrain transport histories of certain ancient sediments. By comparing and analyzing modern and ancient samples, we identified the microtextural differences between aeolian sandstone and fluvial/glacial sediments, highlighting the similarities in microtexture relationships between ancient and modern sediments.