Recent recession of the Larsen Ice Shelf C has revealed microbial alterations of illite in marine sediments, a process typically thought to occur during low-grade metamorphism. In situ breakdown of illite provides a previously-unobserved pathway for the release of dissolved Fe²⁺ to porewaters, thus enhancing clay-rich Antarctic sub-ice shelf sediments as an important source of Fe to Fe-limited surface Southern Ocean waters during ice shelf retreat after the Last Glacial Maximum. When sediments are underneath the ice shelf, Fe²⁺ from microbial reductive dissolution of illite/Fe-oxides may be exported to the water column. However, the initiation of an oxygenated, bioturbated sediment under receding ice shelves may oxidize Fe within surface porewaters, decreasing dissolved Fe²⁺ export to the ocean. Thus, we identify another ice-sheet feedback intimately tied to iron biogeochemistry during climate transitions. Further constraints on the geographical extent of this process will impact our understanding of iron-carbon feedbacks during major deglaciations.

Variations in grain size, clay mineral composition, and stable isotopes (δ¹³C and δ¹⁵N) are closely linked to the sedimentary facies that reflect mineralogical and geochemical modification during the retreat and advance of the Larsen ice shelf. A whole round core of marine sediment (EAP13-GC17, 236 cm below the sea floor) was collected on the northwestern Larsen B embayment of the Antarctic Peninsula during a marine geological expedition (the ARA13 Cruise Expedition by the Korea Polar Research Institute, 2013). Four sedimentary facies (U1–U4) were clearly distinguishable: bioturbated sandy mud (open marine, U1), laminated sandy mud (sub–floating ice shelf, U2), sandy clay aggregates (deglacial, U3), and muddy diamictons (sub-glacial, U4), as well as interbedded silty. Clay minerals, including smectite, chlorite, illite, and kaolinite, were detected throughout the core. An increase in the clay mineral ratio of smectite/(illite + chlorite) was clearly observed in the open marine condition, which was strongly indicated by both a heavier isotopic composition of δ¹³C and δ¹⁵N (−24.4‰ and 4.3‰, respectively), and an abrupt increase in ¹⁰Be concentration (~30 times). An increase in the average values of the crystal packet thickness of illite (~1.5 times) in U1 also indicated sediments transported in open marine conditions. Based on the clay mineral composition in U1, the sediments are likely to have been transported from the Weddell Sea. The clay mineralogical assessments conducted in this region have significant implications for our understanding of paleodepositional environments.

The advantages of X-ray powder diffraction (XRPD) analysis are its non-destructive nature, reliability, fast and easy sample preparation, and low costs. XRPD analysis has been used for mineral identification and the quantitative/qualitative determination of various types of fibrous minerals in asbestos-containing materials (ACMs). In order to test the detection limit of ACMs by XRPDD, standard samples with various concentrations of ACMs (0.1%, 1%, and 3%) were fabricated using three matrix materials (talc, vermiculite, and sepiolite). Asbestiform tremolite and chrysotile were identified in the XRPD profiles of the samples with 1% and 3% ACMs. Their integral intensities were positively correlated with the concentrations. However, the XRPD peak of asbestos was not found in the samples with 0.1% ACMs. Therefore, scanning and transmission electron microscopy were utilized to investigate the samples with a very low concentration of ACMs. Although the ACM concentration (0.1%) was negligible and its direct observation was time-consuming, electron microscopy allowed for the detection of asbestos in several matrix materials. Thus, a combination of XRPD and electron microscopy improve analytical performance and data reliability.

Recently, it has been reported that some chemical reactions are enhanced in below-freezing conditions. Despite the high denudation typical of polar regions, chemical weathering that occurs under ice has not been investigated. In this study, we investigated the dissolution of granite in ice. The mixture of granite and deionized water (DW) or solution adjusted to pH 2 or 3 was split into two groups: the test group was frozen at −20 °C, while the control was maintained at room temperature. After 29 days of batch experiments, the filtrate was analyzed to measure the concentrations of cations and silica. The filtered powder was analyzed to investigate the mineral compositions and crystallinities of the granite before and after the experiments. Despite the low temperature, a significant quantity of cations (Na⁺, K⁺, Mg²⁺, Ca²⁺) were dissolved out, even from the ice samples. During X-ray diffraction (XRD) analysis, the decreased crystallinities of granite in ice samples were identified regardless of the pH condition. To verify the observed freeze concentration effect, the concentration of granite in the ice grain boundaries was observed using optical microscopy with a cold chamber. The low concentration of silica in the ice samples could explain the silica anomaly in polar regions. This study also provides a new perspective for the dissolution mechanism in polar regions.

The second Antarctic station of South Korea was constructed at Terra Nova Bay, East Antarctica, but local seafloor morphology and clay mineralogical characteristics are still not fully understood. Its small bay is connected to a modern Campbell Glacier, cliffs, and raised beaches along the coastline. Fourteen sampling sites to collect surface sediments were chosen in the small bay for grain size and clay mineral analyses to study the sediment source and sediment-transport process with multibeam bathymetry and sub-bottom profiles. Under the dominant erosional features (streamlined feature and meltwater channel), icebergs are the major geological agent for transport and deposition of coarse-sized sediments along the edge of glaciers in summer, and thus the study area can reveal the trajectory of transport by icebergs. Glacier meltwater is an important agent to deposit the clay-sized detritus and it results from the dominance of the illite content occurring along the edge of Campbell Glacier Tongue. The high smectite content compared to Antarctic sediments may be a result of the source of the surrounding volcanic rocks around within the Melbourne Volcanic Province.