South Shetland microplate

South Shetland microplate
Name	South Shetland microplate
Location	Southern Ocean, near Antarctic Peninsula, South Shetland Islands
Type	microplate
Area	~?
Coordinates	~62°S 58°W
Discovery	British Antarctic Survey, Soviet Antarctic Expedition, United States Geological Survey

South Shetland microplate is a small tectonic block located north of the Antarctic Peninsula and adjacent to the South Shetland Islands, involved in the complex interaction between the Antarctic Plate, Phoenix Plate remnants, and the Scotia Plate. The microplate influences regional deformation across the Bransfield Strait, affects volcanism at Deception Island, and plays a role in seismicity recorded by stations operated by British Antarctic Survey, Instituto Antártico Argentino, and United States Antarctic Program. Its study intersects work by institutions such as the Scripps Institution of Oceanography, Lamont–Doherty Earth Observatory, and the National Oceanic and Atmospheric Administration.

Geology and Tectonic Setting

The microplate resides within the tectonic framework bounded by the Antarctic Peninsula, the extinct spreading center of the Phoenix Plate, and the active margin of the Scotia Plate, in a region influenced by the South Shetland Trench, the Bransfield Rift, and the Bellingshausen Sea margin. Regional lithology includes accreted ophiolites comparable to those described at Sanae Glacier exposures, arc-related andesites analogous to those on King George Island and volcanic edifices like Deception Island and Elephant Island, with sedimentary basins resembling sequences from Ellsworth Mountains to Graham Land. Tectonostratigraphic units correlate with plate reconstructions by researchers at Cambridge University and University of Buenos Aires using models from the International Geological Correlation Programme and datasets maintained by Geoscience Australia and the United States Geological Survey.

Boundary Interactions and Fault Systems

The microplate boundary network includes transform faults, back-arc extensional structures, and subduction-related thrusts similar to systems mapped at the South Sandwich Islands and the Alaska-Aleutian transform. Major fault systems include the Bransfield Fault Zone, strike-slip segments analogized to the Peru-Chile Trench transform offsets, and southern counterparts to the Mendocino Fault style discontinuities. Interaction zones have been studied in context with fracture zones identified by NOAA Ship Okeanos Explorer surveys and echo-sounding campaigns by RV Polarstern and RRS James Clark Ross, with geodetic constraints provided by International GNSS Service stations and campaigns by University of Chile and CONICET teams.

Plate Kinematics and Motion

Kinematic models for the microplate derive from GPS, VLBI, and satellite altimetry combining datasets from European Space Agency, NASA, and the Japan Aerospace Exploration Agency. Reconstructions show relative motion between the microplate, the remnant Phoenix Plate, and the Scotia Plate with pole-of-rotation solutions compared to those for the Nazca Plate and South American Plate interactions. Slip-rate estimates have been constrained by work from USGS and researchers at Woods Hole Oceanographic Institution and University of Cambridge, employing methods parallel to reconstructions of the Indian Plate–Eurasian Plate collision and models used in studies of the Mediterranean Sea microplates.

Seismicity and Volcanism

Seismicity around the microplate includes shallow crustal earthquakes, volcanic tremor at Deception Island, and tectonic events recorded by regional catalogs maintained by Incorporated Research Institutions for Seismology, IRIS, and national networks of Chile and Argentina. Volcanism links to magmatic systems comparable to those at Mount Erebus and arc volcanism in the Aleutians, with petrological studies involving Smithsonian Institution scientists and samples archived by British Antarctic Survey repositories. Historic seismic events have been analyzed in the context of tsunamigenic potential as in studies involving the International Tsunami Information Center and hazard assessments by IOC.

Geophysical Studies and Mapping

Geophysical investigations have utilized multibeam bathymetry from NOAA cruises, seismic reflection profiles by RV Polarstern, gravity and magnetic surveys by NASA missions, and tomographic imaging developed at MIT and ETH Zurich. Marine geophysics employed tools such as side-scan sonar similar to systems on RV Pelagia and oceanographic data from ARGO floats, while crustal studies used magnetotelluric arrays comparable to surveys in Iceland and Japan. Mapping efforts integrated GIS products from ESRI and datasets distributed via the Global Seismographic Network and regional compilations by SCAR.

Geological History and Evolution

The microplate evolved during the Cenozoic as the Phoenix Plate underwent fragmentation and subduction beneath the Antarctic Plate, a process recorded in stratigraphic sequences akin to those in the South Orkney Islands and Seymour Island. Paleogeographic reconstructions by teams at University of California, Santa Cruz and University of Leeds link rifting in the Bransfield Strait to Antarctic glaciation events studied by British Antarctic Survey and climate records from Vostok Station and EPICA. Its evolution has been compared to microplate formation elsewhere, including the Aegean Sea and Caribbean Plate microplates, through integrated plate-motion synthesis led by Paleomap Project contributors.

Research and Monitoring Methods

Ongoing research employs continuous GPS arrays from Scripps Institution of Oceanography and episodic campaign data from University of Texas Institute for Geophysics, seismic networks operated by IRIS and SCAR, and marine sampling programs aboard RRS James Clark Ross and RV Polarstern. Geochemical analysis of volcanic glasses follows protocols used at USGS Volcano Science Center and isotopic studies by Max Planck Institute for Chemistry. Collaborative monitoring involves agencies such as NOAA, ESA, UK Natural Environment Research Council, and national Antarctic programs including Instituto Antártico Argentino and Comisión Nacional del Antártico Chileno.

Category:Tectonics Category:Geology of Antarctica