Tectonic Framework of Antarctica

Ian W. D. Dalziel
Institute for Geophysics
Jackson School of Geosciences
University of Texas at Austin

The Antarctic continent consists of two distinct parts.  The East 
Antarctic craton was a segment of the core of the Precambrian 
Gondwanaland supercontinent that was assembled during the 
Neoproterozoic from Archean, Paleoproterozoic, and Mesoproterozoic 
components and existed until fragmentation during the Mesozoic.  
The Transantarctic margin of the craton appears to have rifted 
from another major cratonic entity during the opening of the 
Pacific Ocean basin, also during Neoproterozoic times. West 
Antarctica has been part of the complex circum-Pacific convergent 
margin since the Cambrian, and consists of accreted arc and forearc 
elements, together with displaced fragments of the craton.  The 
continent has been in a south polar location since the Cretaceous 
Period. 

The Antarctic Peninsula overlaps southernmost South America in a 
reconstructions of Gondwanaland based solely on seafloor spreading 
data.  Together with the isolation and displaced strata of the 
Ellsworth Mountains, this indicates that the geography of West 
Antarctica resulted from movement of four major crustal blocks 
during the fragmentation of Gondwanaland, both relative to each  
other and relative to the craton.  Geologic and paleomagnetic  
studies have confirmed this hypothesis.  The present geography 
of the continent was attained prior to the separation of the 
New Zealand microcontinent in the Late Cretaceous.  Uplift of 
the Transantarctic Mountains, together with active volcanism in 
the Ross embayment, indicate Cenozoic and active tectonism.  
The extent and magnitude of this ongoing rifting within crust 
stretched during Gondwanaland fragmentation, especially between 
the Ellsworth-Whitmore, Marie Byrd Land, Thurston Island, and 
Antarctic Peninsula crustal blocks, are major questions of 
global significance currently being investigated using the Global 
Positioning System.  They  could also be addressed with an augmented 
Antarctic seismic array. 

Recent recognition of the lakes beneath the East Antarctic ice sheet 
have led to suggestions that some of them, notably Lake Vostok, 
may be located in an active rift system within the East Antarctic 
craton.  Evidence for activity beyond the possible reactivation of 
old lithospheric weaknesses such as the Lambert-Amery aulacogen 
that predates the opening of the Indian Ocean basin, is minimal.  
However, an augmented Antarctic seismic array could also help 
resolve this important question, as well as contribute to understanding 
of the nature of the adjoining, enigmatically high-relief, Gamburtzev 
Sub-glacial Mountains.