An active Neoproterozoic margin: evidence from the Skelton Glacier area, Transantarctic Mountains

Abstract

Metamorphosed supracrustal rocks in the central Ross Sea sector of the Transantarctic Mountains are of Neoproterozoic age and not Cambrian. They include pillow basalts with a mantle separation age of 700–800 Ma. In the Skelton Glacier area, these rocks experienced two strong phases of deformation that produced folds and associated foliations. Both rocks and structures are cut by a 551 ± 4 Ma unfoliated quartz syenite (late Neoproterozic). The deformation and limited geochemical data suggest an active Antarctic plate margin whose late Neoproterozoic history is markedly different from that of the temporally equivalent rift to drift transition recorded along the autochthonous western margin of Laurentia. If these two cratons were ever contiguous, separation occurred by c. 700–800 Ma.

Tectonic Model for Development of the Byrd Glacier Discontinuity and Surrounding Regions of the Transantarctic Mountains during the Neoproterozoic — Early Paleozoic

“…Indications of convergence are folding of Skelton Group crosscut by plutons dated at 551 ±4 Ma (Rowell et al 1993;Encarnación and Grunow 1996). An even earlier age for the onset of subduction is suggested by detrital zircons of magmatic origin in Starshot Formation dated at 580-560 Ma (Goodge et al 2002).The Beardmore microcontinent converged on the continent from the SSE.…”

“…Identification of the Beardmore orogeny was based primarily on the deformation of Beardmore Group prior to deposition of Shackleton Limestone, but was generalized to encompass any orogenic activity in the Neoproterozoic (Grindley and McDougall 1969).Constraints from detrital zircons in La Gorce Formation now suggest that this folding episode was an Early Cambrian event (perhaps beginning within the last few million years of the Proterozoic) completed by 525 Ma, the beginning of the Atdabanian, which is the age of cross-cutting Wyatt Formation in the La Gorce Mountains and the oldest fossils in the Shackleton Limestone (Palmer and Rowell 1995). In SVL a series of minor plutons span most of the time period 550-505 Ma when the main episode of Granite Harbour Intrusives began, suggesting subduction to the north of the Byrd Glacier discontinuity throughout that time (Rowell et al 1993;Cooper et al 1997;Cox et al 2000;Allibone and Wysoczanski 2002;Read et al 2002).…”

“…Near the base of the marble to the north of Cocks Glacier, polymict, matrix-supported metaconglomerate occurs. The marble overlies a thick succession of clastics, mainly quartzite (Rowell et al 1993). Above the Marble unit is the "Cocks unit" of Cook and Craw (2002) (Cocks Formation of Skinner (1982)), a schistose metasedimentary unit containing thin pillow basalts, and with conglomeratic lenses near its base.…”

“…Above the Marble unit is the "Cocks unit" of Cook and Craw (2002) (Cocks Formation of Skinner (1982)), a schistose metasedimentary unit containing thin pillow basalts, and with conglomeratic lenses near its base. The units of the Skelton Group in the Skelton Glacier area were deformed prior to intrusion of two plutons, each dated at 551 Ma (Rowell et al 1993;Encarnación and Grunow 1996). This relationship itself precludes correlation of Skelton Group (in the Skelton Glacier area) with Byrd Group.…”

Insights in the Neoproterozoic–Early Cambrian transition of NW Argentina: facies, environments and fossils in the proto-margin of western Gondwana

“…An even larger extension has been also proposed, from the highlands of Perú (Díaz Martínez 1996) to Antarctica, on the basis of lithology and trace fossil content (Tessensohn 1982;Jezek et al 1985). Low-grade metamorphic basins of this type are also recorded eastwards in Australia, as part of a major structural unit, resulting from the break-up of Rodinia (Moore 1991;Ross 1991;Storey et al 1992;Rowell et al 1993).…”