New geophysical data from a key region in East Antarctica: Estimates for the spatial extent of the Tonian Oceanic Arc Super Terrane (TOAST)

Abstract

Within Antarctica, eastern Dronning Maud Land (DML) represents a key region for improving our understanding of crustal fragments that were involved in the amalgamation and breakup histories of Rodinia and Gondwana. An aerogeophysical survey was flown during the austral summers 2013/14 and 2014/15 to explore the largely ice-covered region south and east of Sør Rondane. Here, we present 40,000 new line kilometer of aeromagnetic data gathered across an area of ca. 295,000km2 with a 10km line spacing. Magnetic domains, major lineaments, locations, and depths of magnetic source bodies are detected from total field data, their tilt derivative, pseudo-gravity, and analytical signal transformations, and from Euler Deconvolution maps. These data are integrated with exposure information from the Sør Rondane, Belgica and the Yamato mountains in order to identify the eastern spatial extent of a major juvenile Early Neoproterozoic crustal province, the Tonian Oceanic Arc Super Terrane (TOAST). Magnetic data reveal a characteristic pattern with NW-SE trending elongated magnetic anomalies to the south of Sør Rondane. This area is interpreted as the eastward continuation of the distinct SE DML Province and therefore of the TOAST. Major curvilinear magnetic anomalies of several hundreds of kilometers length dissect the region south and southwest of Sør Rondane. These may represent boundaries of individual oceanic arc terrane or alternatively major Pan-African shear zones. A significant change of the magnetic anomaly pattern ca. 800km inland of Sør Rondane may indicate the southern minimum extent of the TOAST. Magnetic anomalies of varying size, amplitude, and orientation suggest a complex transitional area between the Belgica and Yamato Mts., which appears to separate the TOAST from an Indo-Antarctic craton to the east. The new data suggest that the TOAST is comparable in size with the Antarctic Peninsula and therefore represents a significant piece of Neoproterozoic crustal addition. It originated at the periphery or outboard of Rodinia and is a remnant of the Mozambique Ocean.