PREDICTING MINERALOGY OF MODERN SEDIMENT USING A GLOBAL SAND DATABASE

This research aims to better understand how Earth-surface processes are manifested in sediment and the sedimentary archive. Framework grain mineralogy of terrigenous sand and sandstone has long been used as a proxy for sedimentary provenance. Often used to infer the tectonic setting of ancient sandstone depositional environments, mineral proportions can also provide information about boundary conditions within sediment routing systems such as climate and source terrane lithology, and Earth-surface processes like sediment composition refinement with transport distance. This study began by asking these complementary questions: (1) can the final modal composition of sand be predicted if boundary conditions are known; and (2) can sand composition in basin samples be used to determine the relative control of the environmental factors that generate sediments? We investigate these questions by analyzing Pleistocene-to-modern aged samples where provenance and boundary conditions are known with certainty, using existing data from published studies and new data from marine sand samples across the globe.

To date, modal point count data from 2,640 sand samples have been compiled from 41 publications. This dataset spans all continents except Antarctica. Fluvial and deep-water depositional environments constitute the majority of the dataset (70% and 13%, respectively), with lacustrine, aeolian, littoral, and shallow-marine environments making up the remainder. Onshore samples lack feldspathic sand relative to quartzose and lithic sand. Feldspathic sands are more prevalent in deep-water environments; this is possibly related to many samples in the compilation being in proximity to volcanic arc sources. Pure quartzose sands (i.e., total quartz > 95%) comprise 10% of the database and only exist between latitudes 31.6°N and 34.2°S. This is consistent with previous studies that have documented the effect of tropical climate on increasing quartz concentration. Future analysis will compare modal composition of fluvial and marine samples to parameters within their upstream catchments.