Di Roberto A., P. Del Carlo, A. Bertagnini, E. Colizza,
M. Pompilio, F. Giglio, F. Florindo, (2024).
Annals of Geophysics, https://doi.org/10.4401/ag-9102

Abstract

In this study, we investigate silica spherules with a diameter <1.25 mm from sediment cores retrieved from the northern Drygalski Trough, during the Italian Antarctic Research Programme (PNRA) expeditions in 1999 and 2002. In the past, these unique spherules have been a subject of interest due to their distinctive characteristics. Despite previous hypotheses on their origin, a comprehensive discussion on their formation mechanism and implications in marine sediments was lacking. Our analysis encompasses the depositional environment, morphology, internal texture, major element composition, and age determination through radiocarbon dating (14C) and 40Ar‑39Ar dating of spherule-containing sediments. By integrating our findings with a critical review of existing literature, we propose that spherules form by cyclical chemical precipitation of silica when silica-rich freshwater mixed with seawater during extensive events of ice melting. We also tentatively suggest that these spherules possibly represent a proxy for significant meltwater production and discharge into the Antarctic Ocean. This research contributes to a better understanding of silica spherules in polar marine environments and their implications for past climate conditions.