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The Transantarctic Mountains (TAM) are one of the world's longest continental rift flank uplifts, with an along strike length of more than 3500 kilometers. They rise from sea level to elevations of 4000 meters just 40 kilometers from the coast. 100 kilometers offshore in the Ross Sea, the Victoria Land Basin contains up to 14 kilometers of sediment deposited during Jurassic-Recent rifting. The TAM and adjacent basins thus comprise a large, continental scale rift system, comparable in size to better known continental rifts such as the East African Rift System, the Great Escarpment of Southern Africa, and the Basin and Range province of western North America. The remarkable change in elevation over so small a lateral distance is distinctive of the TAM system, however.
|Sattelite image compiled by National Remote Sensing Centre, UK. Data from NOAA.|
Important structural differences exist between the TAM and the other continental rift systems mentioned. In the other rifts, the asymmetry of extension changes polarity along strike at a spacing of tens to hundreds of kilometers. These changes in asymmetry polarity are so common that they are considered fundamental features of rifts. It is surprising, then, that the TAM show no evidence for a change in asymmetry polarity along their entire length. Sense of offset is consistently down to the east. This conclusion is especially well documented in the 2000 kilometer long Ross Embayment sector of the TAM due to better exposure in this sector.
Another difference between the TAM and the other rift systems is that the TAM demarcate a primary lithospheric boundary between Archean-Proterozoic lithosphere in East Antarctica and Paleozoic-Mesozoic accreted terranes in West Antarctica. The TAM rift system appears to reactivate a long-lived zone of crustal weakness at the edge of the East Antarctic craton. Although other rift systems may reactivate old structures in some cases, they typically do not separate domains of different lithospheric age.
Because the 4 kilometer high TAM flagrantly violate McKenzie's (1978) model for lithospheric stretching and initial subsidence, workers on the TAM system have produced many models to explain the large uplift of the rift flank. These models are similar in form to explanations for the uplift of other rift shoulders around the world, but the models differ in detail. A comparison of the TAM system with other rifts can be found in the comparison section.
Questions? Comments? Contact me. Last updated 4/7/02.
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