Water-Mass Interactions Regulate the Occurrence of Silica Spherules, Microtektites, and Carbonate Preservation on the Ross Sea Continental Shelf

The role of the Ross Sea continental shelf in global carbon cycling has been studied under variable ecological conditions. Here, the spatial distributions of microfossil assemblages and silica-rich spherules from surface sediments across the Ross Sea continental shelf are integrated to provide additional insights into the interaction among water masses. The spatial distribution of diatoms and benthic foraminifera reflects spatial gradients in sea-ice concentration and hydrodynamics. Silica spherules and microtektites identified in the Drygalski and Joides Troughs were classified by geochemical composition to explore potential links between characteristic elemental enrichments and water masses. Three compositional patterns of silica spherules were identified under relatively turbulent hydrodynamic conditions with silica supplied by meltwater: (1) specimens with elevated Nb and Zr distributed under consolidated sea ice conditions influenced by High-Salinity Shelf Water (HSSW); (2) Rb-enriched specimens distributed in the Drygalski and Joides Troughs with Modified Circumpolar Deep Water (MCDW) incursion; (3) ordinary specimens without specific characteristics. The microtektites characterized by high Cr are compositionally consistent with Australasian Transantarctic Mountain (AUS/TAM) types and potentially transported by HSSW circulation. More foraminiferal fragments under higher hydrodynamic conditions suggest that the water-mass interactions may contribute to carbonate preservation, in addition to water chemistry.