Provenance, transport and diagenesis of sediment in polar areas: a case study in Profound Lake, King George Island, Antarctica

Abstract

Detailed scanning electron microscopy (SEM) micro-texture and mineralogical analysis of lacustrine sediment recovered from Profound Lake (also known as Uruguay Lake), Antarctica, was conducted in the foreland area of the Collins Glacier, King George Island. Very coarse and coarse sand grade size fractions (2 mm -600 μm) were examined with SEM/ energy dispersive spectrometry, while the total sand fraction and fines (silt + clay) were examined using x-ray diffraction to determine relationships to source rock, weathering and transport history and long-term clay mineral weathering, all of which are poorly understood in polar areas. The mineralogy of these sediments was compared with petrographical information of the country rock to identify potential detrital sources. The association of recovered detrital minerals, sometimes strongly pre-weathered, supports release from source rock of basaltic and andesitic compositions. The micro-texture analysis of quartz, magnetite and various plagioclase grains show micro-features that reveal a complex weathering-diagenesis history tentatively extending into the Paleogene. The bedrock was eroded mostly by glacial processes and mechanical action presumed to result from glacial crushing. Alteration minerals, likely the product of pre-weathering, are probably sourced from weathered bedrock during contact with the sub-aerial atmosphere prior to entrainment. However, amorphous silica precipitation indicates weathering subsequent to glacial erosion from the source bedrock. Cracks of variable dimensions are mostly characteristic of either frost weathering or glacial transport, and involve mechanical and chemical processes.

Characterization and distribution of clay minerals in the soils of Fildes Peninsula and Ardley Island (King George Island, Maritime Antarctica)

“…Vermiculite has also been described in Fildes Peninsula in previous works (Poggere et al ., 2017; Hernández et al ., 2018). Surface weathering or the low-grade metamorphism and hydrothermal alteration that affected the volcanic rocks from Fildes Peninsula (Venum & Nejedly, 1990; Willan & Armstrong, 2002; Montecinos de Almedia et al , 2003; Bastias et al , 2013) might have transformed biotite and chlorite into vermiculite via interstratified chlorite-vermiculite (Wilson, 1999).…”

Surface Water Stable Isotope Geochemistry in King George Island, Antarctica

“…Further, calibration of climate proxies is needed and a first step in this approach is to understand the links between climate and the stable isotope composition of lake waters. Lakes in KGI have been shown to contain sediments rich in carbonates covering at least Holocene (Mäusbacher et al, 1989;Hernández et al, 2018) thus offering the possibility to reconstruct the dynamics of sedimentation and past climate variability, provided that we understand what the proxies in these sediments record in terms of climate elements.…”