Sedimentology of the grounding zone of the Kamb Ice Stream, Siple Coast, West Antarctica

• Main Author: Calkin, Theo
• Format: Thesis
• Language: unknown
• Published: 2021
• Subjects: Sedimentology; grounding line; grounding zone; Siple Coast; structure from motion; rainout; melt out; hot water drill; sedimentary facies; diamicton; School: School of Geography; Environment and Earth Sciences; Unit: Antarctic Research Centre; 040310 Sedimentology; 960399 Climate and Climate Change not elsewhere classified; Degree Discipline: Geology; Degree Level: Masters; Degree Name: Master of Science; Antarctic; Kamb Ice Stream; Siple; West Antarctic Ice Sheet; West Antarctica; Whillans; Whillans Ice Stream; Antarc*; Antarctica; Ice Sheet; Ice Shelf
• Online Access: https://doi.org/10.26686/wgtn.16906837.v1; https://figshare.com/articles/thesis/Sedimentology_of_the_grounding_zone_of_the_Kamb_Ice_Stream_Siple_Coast_West_Antarctica/16906837

The grounding line of the Siple Coast incorporates six major ice streams, which together drain around a third of the West Antarctic Ice Sheet. Previously, the ~2000 km-long feature had only been sampled and directly observed at Whillans Ice Stream. This thesis examines glaciomarine sediment and processes operating at the presently stagnant Kamb Ice Stream (KIS) grounding zone ~3.3 km seaward of the modern grounding line (Lat. -82.78, Long. -155.16), where the ice is 590 m thick and overlies a 30 m thick water column. KIS-GZ is the planned site for a deep drilling project in 2023. The sea floor was accessed using a hot water drill in the 2019/20 Antarctic field season. A remotely operated submersible (‘Icefin’) was deployed under the ice shelf, which provided 800 m of sea floor video toward the grounding line. A small number of short (~0.6 m) gravity cores were collected from the seafloor, one of which was examined in this study. The Icefin video imagery was processed using Structure-from-Motion (SfM) software, enabling the identification of two previously unrecognised sea floor sedimentary facies. One is defined by ubiquitous cm-scale ripples in fine-medium sand, where the ripples are aligned with the prevailing tidal currents flowing parallel to the grounding line. Observed current speeds are too low for the ripples to be generated under the modern oceanographic regime. The second facies is defined by abundant dropstones in mediumcoarse sand. A transition zone separates the two facies. Previously unidentified decimetre-scale bedforms are present in the transition zone and near the borehole. The lithological, geochemical, and microfossil properties of the gravity core were analysed. The core sediment is sandy diamicton with weak stratification defined by decimetre-scale changes in clast abundance. Mineral counts, zircon ages, Nd/Sr isotopes, and an immature composition indicate this sediment is sourced within the Kamb catchment. The core also contains reworked late Oligocene-late Miocene diatoms. Quaternary ...