The structural evolution of the Straumsnutane and western Sverdrupfjella areas, western Dronning Maud Land, Antarctica: implications for the amalgamation of Gondwana

• Published in: Geological Magazine
• Main Authors: Bumby, Adam, Grantham, Geoffrey H., Moabi, Neo Geogracious
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2020
• Subjects: Geology; Dronning Maud Land; Ahlmannryggen; Sverdrupfjella; Ritscherflya; Straumsnutane; Antarc*; Antarctica; DML
• Online Access: http://dx.doi.org/10.1017/s0016756819001523; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756819001523

Abstract The study area is located across the Kalahari Craton – Maud Belt boundary in Dronning Maud Land (DML), Antarctica. The ∼1100 Ma Maud Belt in the east is situated where the ∼900–600 Ma East African and ∼530–500 Ma Kuunga orogenies overlap. The Kalahari Craton cover in the west of the study area comprises ∼1100 Ma Straumsnutane Formation lavas in Straumsnutane. In Straumsnutane, early ∼1100 Ma low-grade structures suggest top-to-the-NW deformation. Younger ∼525 Ma structures suggest conjugate top-to-ESE and -WNW transport under low-grade conditions. Western Straumsnutane and Ahlmannryggen do not show the same complex deformation, the intense deformation being restricted to NE Straumsnutane along the eastern margin of the Kalahari Craton. In Sverdrupfjella, in the east, the Maud Belt is underlain by medium-grade, deformed ∼1140 Ma supracrustal gneisses and younger intrusions. Four deformation phases in the gneisses comprise D 1 + D 2 with top-to-the-N and -NW folds, D 3 top-to-the-S and -SE folding and D 4 brittle faulting. Syn-D 3 emplacement of granitoid veins is inferred at ∼490 Ma. Comparison of the deformation vergence of NE Straumsnutane with western Sverdrupfjella suggests D 1 in Straumsnutane is correlatable with D 1 + D 2 Mesoproterozoic structures in western Sverdrupfjella. D 2 deformation in Straumsnutane can be correlated with D 3 structures and Cambrian-age granites in Sverdrupfjella. D 2 deformation in eastern Straumsnutane and D 3 in western Sverdrupfjella are inferred to have occurred in a mega-nappe footwall, implying the Ritscherflya Supergroup cratonic cover in eastern Straumsnutane was partially submerged in the footwall, the mega-nappe formed during Gondwana amalgamation, involving collision between N and S Gondwana in the Kuunga Orogeny, ∼530–500 Ma ago.