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Meta-analysis of Cryogenian through modern quartz microtextures reveals sediment transport histories
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  • Jocelyn N Reahl,
  • Marjorie D Cantine,
  • Julia Wilcots,
  • Tyler J Mackey,
  • Kristin D Bergmann
Jocelyn N Reahl
Massachusetts Institute of Technology, Massachusetts Institute of Technology

Corresponding Author:[email protected]

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Marjorie D Cantine
Massachusetts Institute of Technology, Massachusetts Institute of Technology
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Julia Wilcots
Massachusetts Institute of Technology, Massachusetts Institute of Technology
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Tyler J Mackey
Massachusetts Institute of Technology, Massachusetts Institute of Technology
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Kristin D Bergmann
Massachusetts Institute of Technology, Massachusetts Institute of Technology
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Abstract

Quantitative scanning electron microscopy (SEM) quartz microtextural analysis 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 9 new samples from active aeolian and glacial environments. Our results demonstrate that PCA can group microtextural samples by transport mode and differentiate between aeolian and fluvial/glacial transport modes 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 Bråvika Member (Svalbard). Integrating PCA with field observations, we find evidence that the Bråvika 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.