7. Ross orogen

The age determinations compiled in Table 3.3 can be used to reconstruct the geologic history of the Ross Orogen in southern Victoria Land with due regard to several self-evident considerations ... 

The Ross Orogen of southern Victoria Land extends across the David Glacier into the southern part of the Wilson Terrane of northern Victoria Land. The geology of this part of the Transantarctic Mountains in Fig. 4.6... 

The boundary between the Terra-Nova-Bay area and the main part of the Wilson terrane is not defined because the Ross Orogen continues from southern Victoria Land through the Terra-Nova-Bay area into the Wilson Terrane of northern Victoria Land without discernible interruption. The Wilson Terrane extends from the Terra-Nova-Bay area north to the Oates Coast of Antarctica and is separated from the Bowers Terrane by the Lanterman fault zone in Fig. 4.2. The Wilson Terrane extends east across the Renifick Glacier and includes the Lanterman and Salamander ranges which form its eastern province. ... 

Which of the three terranes contains the Ross Orogen of southern Victoria Land ... 

Stump E (1995) The Ross orogen of the Transantarctic Mountains. Cambridge University Press, Cambridge Stump E, Gootee B, Talarico F (2006) Tectonic model for development of the Byrd-GIader discontinuity and the surrounding... 

Goodge (1997) further pointed out that the rocks of the Beardmore Group were folded less than 600 million years ago, as indicated by U-Pb dates of detrital zircons (Walker and Goodge 1994), but more than 500 million years ago, based on age determinations of the post-kinematic Hope Granite. The evidence for a continuous spectrum of dates within the Ross orogen from Late Neoproterozoic to Ordovician is best accounted for by one continuous and extended tectonic process encompassed within the Ross Orogeny. 

The Ross orogenic cycle constitutes a broad and diachronous sequence of geologic events during the latest Neoproterozoic to early Paleozoic manifested by different strain histories in rocks occupying different crustal levels. 

Future generations of geologists may want to fine-tune this model but for the time being it is a realistic synthesis of the geological processes that produced the Ross orogen. 

The insights gained by these specialized studies of the central Transantarctic Mountains must be examined critically to determine whether the master hypothesis concerning the formation of the Ross orogen presented by Stump (1995) is still valid and still explains satisfactorily the deposition of detrital sediment along a passive rift margin which later evolved into an active subduction zone that caused the deformation and regional metamorphism of the rocks that now form the basement complex of the central Transantarctic Mountains. 

After a lengthy period of uplift and erosion, sedimentary rocks of Permian age described by Long (1965) were deposited on the Kukri Peneplain which formed by erosion of the rocks of the Ross orogen. 

The granitic rocks of the Granite Harbor Intrusives occur in the core of the Ross orogen from the Wilson Terrane of northern Victoria Land to the Ohio Range of the Horlick Mountains and beyond. This group of rocks is characterized by a wide range of chemical... 

Mountains that is illustrated in Fig. 7.17. The results generally eonfirm the master hypothesis eoneerning the origin of the Ross orogen presented by Stump (1995). 

In this way, the Shackleton Range completes a trend that began in the Thiel Mountains and continued in the Pensacola Mountains both of which are inCTeasingly displaced from the subduction zone along which the Ross Orogen formed by compression from east to west at about 500 Ma. However, Clarkson (1982) reported that the Cambro-Ordovician rocks at the western end of the Shackleton Range strike north and south. 

Fig. 8.23 The continental collision model considers that the structure of the Shackleton Range is the result of compression caused by the collision of the East Antarctic craton with the African continent. The resulting closure of the Mozambique ocean is recorded by the Mozambique fold belt. The Ross Orogen, which underlies the Transantarctic Mountains formed by compression of sedimentary and volcanic rocks in an active subduction zone followed by intrusion of the anatectic granitoids of the Granite Harbor Intrusives. Both tectonic processes affected the deposition and subsequent deformation and metamorphism of the basement rocks of the Shackleton Range (Adapted from Tessensohn et al. 1999a)...

Rex DC (1972) K-Ar age determinations on volcanic and associated rocks form the Antarctic Peninsula and Dronning Maud Land. In Adie RJ (ed) Antarctic geology tmd geophysics. Universitetsforlaget, Oslo, Norway, pp 133-136 Rowell AJ, Rees MN, Evans KR (1992) Evidence of major Middle Cambrian deformation in the Ross orogen, Antarctica. Geol 20 31-34. 

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