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

Abstract

Abstract. The Byrd Glacier discontinuity is a major tectonic boundary crossing the Ross Orogen, with crystalline rocks to the north and primarily sedimentary rocks to the south. Most models for the tectonic development of the Ross Orogen in the central Transantarctic Mountains consist of two-dimensional transects across the belt, but do not address the major longitudinal contrast at Byrd Glacier. This paper presents a tectonic model centering on the Byrd Glacier discontinuity. Rifting in the Neoproterozoic produced a crustal promontory in the craton margin to the north of Byrd Glacier. Oblique convergence of a terrane (Beardmore microcontinent) during the latest Neoproterozoic and Early Cambrian was accompanied by subduction along the craton margin of East Antarctica. New data presented herein in support of this hypothesis are U-Pb dates of 545.7 ±6.8 Ma and 531.0 ±7.5 Ma on plutonic rocks from the Britannia Range, directly north of Byrd Glacier. After docking of the terrane, subduction stepped out, and Byrd Group was deposited during the Atdabanian-Botomian across the inner margin of the terrane. Beginning in the upper Botomian, reactivation of the sutured boundaries of the terrane resulted in an outpouring of clastic sediment and folding and faulting of the Byrd Group.

Detrital mineral ages from the Ross Supergroup, Antarctica: Implications for the Queen Maud terrane and outboard sediment provenance on the Gondwana margin

“…Alkaline magmatism continued into the early Cambrian (~530 Ma) in southern Victoria Land (Rowell et al, 1993;Cooper et al, 1997;Read et al, 2002;Mellish et al, 2002;Cottle and Cooper, 2006a), intruding deformed metasedimentary rocks. Calc-alkaline magmatism was prevalent between~530 and 480 Ma (Encarnación and Grunow, 1996;Allibone and Wysocazanski, 2002;Vogel et al, 2002;Paulsen et al, 2013), but may potentially have locally initiated as early as 545 Ma (Cottle and Cooper, 2006b;Stump et al, 2006;Goodge et al, 2012). Widespread emplacement of largely undeformed granites occurred after~500 Ma (Borg et al, 1990;Stump, 1995;Encarnación and Grunow, 1996;Allibone and Wysocazanski, 2002).…”

“…,Mellish et al (2002),Myrow et al (2002),Read et al (2002),Vogel et al (2002);Goodge et al (2002),Curtis et al (2004),Goodge et al (2004a,b),Paulsen et al (2004),Stump et al (2004),Wysoczanski and Allibone (2004),Cottle and Cooper (2006a,b),Stump et al (2006Stump et al ( , 2007,Talarico et al (2007),Paulsen et al (2008),Cooper et al (2010),Goodge et al (2012), andPaulsen et al (2013).…”

Time–space focused intrusion of genetically unrelated arc magmas in the early Paleozoic Ross–Delamerian Orogen (Morozumi Range, Antarctica)

“…However, there is no robust evidence that the Ross Orogeny and subduction-related arc magmatism started before c. 540-530 Ma, and the diachronous starting of the orogenic cycle in Antarctica and Australia has recently been questioned (Gibson et al, 2011;Turner et al, 2009). Nevertheless, the age and geochemical patterns of intrusive rocks suggest oblique convergence along a tectonically segmented margin (Encarnación and Grunow, 1996;Goodge, 2002;Goodge et al, 2004Goodge et al, , 2012Rocchi et al, 1998;Stump et al, 2006). The latest magmas emplaced in the Ross Orogen are about 480 Ma, and evidence for younger (460-440 Ma) amagmatic contractional tectonic activity in Victoria Land is likely related to the early stages of the formation of the Lachlan Fold Belt (Di , which is best developed in southeastern Australia (Glen et al, 2007).…”

Morphotectonic architecture of the Transantarctic Mountains rift flank between the Royal Society Range and the Churchill Mountains based on geomorphic analysis

“…Davey, 1981;Cooper et al, 1991;Tessensohn, 1994;Mazzarini et al, 1997). Evidence examined by Stump et al (2006) suggests that the discontinuity evolved into an oblique subduction boundary during the Ross Orogeny, thus suggesting Ross Orogen control over the accommodation zone.…”