Clay minerals and elemental composition of smectites in the marine sediment from the southwest Ross Sea and implication for their provenance and sediment input changes after the last glacial period

Abstract

Smectite in detrital sediments can be composed of various proportions of Al, Mg, and Fe, indicating the sediment sources derived from the bedrock or from the sedimentary strata. Comparing the elemental composition of smectites can help to define sediment provenance in relation to paleo-environmental changes, especially glacier retreat. However, few studies of mineralogical and geochemical properties of clay minerals in marine sediment from the southwest Ross Sea have been conducted. Here, this study investigates the clay mineralogy and elemental composition of smectites during the last glacial period to the latest Holocene sediment in cores RS15-GC16B (southern Drygalski Trough), RS15-GC78 (offshore of Mawson Glacier), and RS15-GC80 (Mackay Glacier front) deposited in the southwest Ross Sea sector. It might be necessary to understand variabilities and distribution of elemental compositions in smectites in the southwest Ross Sea and their provenance, and to reconstruct sediment transport through the glacier changes. Indeed, two types of smectite (Al-rich and Al-Fe rich) were identified in core RS15-GC16B from the southern Drygalski Trough, indicating that some sediments were supplied from glaciogenic debris containing Al-Fe rich smectite by the northward advance of the East Antarctic glacier during the glacial period. In contrast, only Al-rich smectite in core RS15-GC16B (the southern Drygalski Trough) were identified during the deglacial period. Al-rich smectite is probably originated from subglacial erosion of sedimentary strata from the David Glacier. This finding implies different sources during glacial and deglacial period deposited at core RS15-GC16B, although that show only minor difference in smectite contents. Overall, these results highlight importance of analysis of the elemental composition of smectites in tracing sediment sources and their transport pathways during the East Antarctic glacier retreat.