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| Mawson Lineament | |
|---|---|
| Name | Mawson Lineament |
| Type | Lineament / shear zone |
| Location | East Antarctica |
| Named for | Sir Douglas Mawson |
Mawson Lineament is a major crustal-scale linear feature in East Antarctica associated with a long, discontinuous zone of deformation that transects Precambrian terranes and influences the distribution of crustal blocks across the Antarctic Shield. The feature has been interpreted as a transcurrent shear zone, a suture between continental fragments, or a reactivated Proterozoic boundary, and it has been investigated through aeromagnetic, gravity, and seismic studies alongside field mapping in outcrop exposures such as the Gressitt Glacier region. Its significance extends to interpretations of Rodinia and Gondwana reconstructions, paleogeographic models, and correlations with orogenic belts on other continents such as the East African Orogen and the Fennoscandian Shield.
The Mawson Lineament is described in literature as a linear geologic fabric or zone of high strain cutting across crustal domains of Antarctica and influencing the juxtaposition of terranes like the Mawson Craton, the Wilkes Land block, and adjacent Proterozoic provinces. Early recognition came from regional aeromagnetic and satellite imagery patterning linked to linear magnetic anomalies, which spurred integrated studies by institutions such as the Australian Antarctic Division, the British Antarctic Survey, and the Scientific Committee on Antarctic Research. Interpretations emphasize its role in continental assembly and breakup events that involve plates and microcontinents such as East Antarctica, India, Australia, and fragments correlated with the Antarctic Peninsula.
The lineament manifests as an alignment of deformation features including mylonitic fabrics, shear zones, and discontinuous fault segments observed in exposures and inferred from geophysical lineations. Lithologies affected range from Archean gneisses of the Mawson Craton to Mesoproterozoic supracrustal belts and granitoid intrusions correlated with the Gawler Craton and Grampian Orogen-equivalent terranes. Structural elements include steep dextral shear senses, conjugate fault sets, and metamorphic gradients that grade from amphibolite to granulite facies near deeply buried segments implicated in crustal thickening episodes linked to the Pan-African Orogeny and older orogenic episodes comparable to the Grenville Province.
Competing models for the origin of the Mawson Lineament invoke (1) a Proterozoic suture marking collision between microcontinents related to reconstructions of Rodinia, (2) a reactivated intracontinental shear zone linked to Neoproterozoic rifting and the assembly of Gondwana, and (3) a long-lived lithospheric-scale transform expressed during Mesozoic breakup of southern Pangea and the opening of the Indian Ocean. Correlations have been proposed with structural trends in the Kalahari Craton, the Kendall Belt analogues, and elements of the East African Rift system when considering later reactivation. The feature is therefore invoked in plate reconstructions that include Laurentia, Siberia, Baltica, and Avalonia fragments.
Detrital zircon ages, U–Pb isotopic data, and Sm–Nd whole-rock signatures from rocks adjacent to the lineament yield age spectra tied to Archean provinces (ca. >2.5 Ga), Mesoproterozoic crystallization events (ca. 1.6–1.0 Ga), and Neoproterozoic metamorphism and magmatism (ca. 1.0–0.54 Ga). These data enable correlation with the Sturtian glaciation-age tectonism and linkages to magmatic events recorded in the Transantarctic Mountains, Wilkes Land orogenic belts, and continental-margin arcs comparable to those preserved in Tasmania and the Gawler Craton. Stratigraphic relationships incorporate reworked supracrustal sequences, granitoid intrusions, and late-stage sedimentary basins recognized in onshore and offshore seismic profiles.
High-resolution aeromagnetic grids, regional gravity anomaly maps, and passive seismic tomography have delineated linear anomalies consistent with the Mawson Lineament’s trace beneath ice cover and sediment. Satellite-based radar altimetry and ice-penetrating radar have constrained subglacial topography and bedrock expression where the lineament intersects drainage systems such as major outlet glaciers and subglacial basins mapped by the Antarctic Geological Drilling Program and the International Ocean Discovery Program. Interpretations integrate datasets from agencies including the National Aeronautics and Space Administration, the Australian Antarctic Data Centre, and the Geological Survey of Norway for global correlation.
The Mawson Lineament forms a key boundary separating cratonic and orogenic domains: to the west lie cratonic fragments analogous to the Australian Shield and Yilgarn Craton provinces, while to the east are orogenic belts akin to the Ross Orogen and elements correlated with the Kerguelen Plateau-related magmatism. Cross-boundary correlations have been proposed with suites on India, the Prince Charles Mountains, and terranes linked to the Cairo–Hornsby structural corridor in reconstructions. These relationships inform models for continental accretion, delamination, and lithospheric reworking during Proterozoic and Phanerozoic times.
Recognition of the Mawson Lineament evolved from early 20th-century reconnaissance by expeditions associated with figures such as Sir Douglas Mawson and subsequent systematic mapping by national programs including the Australian Antarctic Division, the United States Geological Survey, and the British Antarctic Survey. From the mid-20th century, integration of geochronology pioneered by laboratories at ANU and USGS accelerated comprehension, while collaborative initiatives under SCAR facilitated multinational surveys, drilling campaigns, and comparative studies tying the lineament to global orogenic events like the Pan-African Orogeny and the Grenville orogeny.
Category:Geology of Antarctica Category:Structural geology Category:Geologic lineaments