Linking Sedimentary Textures to Neoproterozoic Climate Dynamics

The Cryogenian Bråvika Member in Northeastern Svalbard sits at the boundary between two different climate states: the unglaciated interval between the two Cryogenian ice ages, and the Marinoan glaciation. Large-scale sedimentological and isotopic studies of the Bråvika Member and the surrounding stratigraphy have identified three possible depositional environments for the Bråvika Member: a fluvial proglacial, an aeolian, or a tropical fluvial environment.

These different interpretations highlight the uncertain relationship between the Marinoan glaciation and the Bråvika Member. In addition, this relationship is important for understanding if the Marinoan glaciation was laterally continuous, with few or no subaerially exposed areas ( "hard Snowball Earth" models) or discontinuous, with some subaerially exposed land areas (the "soft Snowball" or "slushball" models). Radical changes in ecology and evolution led to the emergence of complex animal life during and after the Cryogenian glaciations. Correctly identifying the environments in which these changes occurred is critical for understanding the role of environment and temperature in shaping animal evolution on Earth.

This study uses a combination of petrography, energy-dispersive spectroscopy (EDS), scanning electron microscope (SEM) microtextural analysis, and statistical analysis to characterize the microtextures of quartz grains from the mid-lower Bråvika Member in Buldrevågen, Svalbard, and is the first study to perform microtextural analysis on the Bråvika. Samples from the mid-lower Bråvika Member from Buldrevågen most closely resemble samples from known periglacial aeolian facies. This evidence, together with field evidence for syndepositional ice and aeolian transport, suggests that the mid-lower Bråvika Member in Buldrevågen represents a periglacial aeolian facies, implying some terrestrial environments were subaerially exposed during the Marinoan glaciation.