PRE-GLACIAL HISTORY OF SOUTH VICTORIA LAND 293 



rivers were betrunked, in their lower courses, through the formation of the Ross Sea 

 senkimgsfeld, and were dammed back in their upper courses by the horst. Thus 

 lakes probably gathered to the west of the horst, overflowing to north and west of 

 the horst in the direction of Oates Land, or bending eastwards through the low 

 gap between Mount George Murray and the Drygalski Glacier Tongue. Later, as 

 glaciation developed, the ice rose high on the inland side of the horst, until it 

 poured down the old shallow river valleys and swept bodily over all the wide low 

 sags in the horst, especially between the Royal Society Range and Mount Nansen. 

 During the prolonged glaciation that followed the old mature river valleys were cut 

 down by the ice-flood to their present vast depth, and perhaps all traces of former 

 river action, except that of the original trend of the mature valleys, became 

 obliterated. 



Still another view, advocated by T. Griffith Taylor, is that the horst was not at 

 all notched by rivers, but that the cutting of the outlet valleys was the work of 

 cirque recession on either side of the horst, the cirques incising low cols over which, 

 later, the swelling ice-flood swept. 



This question of the past physiography of South Victoria Land, in Pre-Pliocene 

 glacial times, is also of considerable interest in relation to any estimates of the 

 probable area of concealed coalfields to the westward of the Antarctic Horst. The 

 almost meridional trend of the horst, combined with a general steady slope from 

 near Shackleton's Farthest South to the coast nearly due south of the Balleny 

 Islands, suggests that probably a large subsequent river eroded a wide channel 

 following a subsequent course parallel to the Antarctic Horst, and entering the sea 

 perhaps between Cape North and Adelle Land. If such a valley with its tributaries 

 were eroded in Eocene, Miocene, and early Pliocene time, it would obviously have 

 made great inroads on the former area of the Beacon Sandstone coalfield lying to 

 the west of the horst. As the productive coal seams lie at some height up in the 

 series, these seams would have suffered much from erosion. 



This consideration shows how futile it would be to attempt anything more than 

 an extremely rough estimate as to the possible areas of productive coal under the 

 concealed part of this coalfield, where it is overlaid by a thickness of probably from 

 2000 to 3000 feet of glacier ice. 



Fig. 66 illustrates the possible shifting of the position of the main divide of 

 the Antarctic continent, in the South Victoria Land region, since the formation 

 of the Antarctic Horst, probably in Early Tertiary, possibly in Miocene or even in 

 Early Pliocene time, in regard to the latest of the tectonic movements. 



If the Ross Barrier were to disappear, and we could see the surface relief of the 



floor of Ross Sea, we should probably see as many long submarine morainic mounds 



as there are glaciers of any importance emptying into Ross Sea. Probably these 



mounds would extend considerably more than 100 miles from the shore-line. 



Possibly the moraines of the Ross Barrier may now be in process of being 



2 P 



