sedimentation have been reported from Deep Sea Drilling Project 

 holes in the north Atlantic, Caribbean, central and northern Pacific, 

 and the Melanesian region. It appears that the hiatuses in Indian 

 Ocean sediment accumulation resulted from major changes in 

 oceanic circulation that occurred as Australia separated from 

 Antarctica about 50 million years ago. 



Drilling near Antarctica expanded knowledge of the development 

 and history of the icecap that now covers the continent. Studies of 

 sediments recovered from the cores has demonstrated that extensive 

 glaciers have covered the Antarctic continent since at least 20 

 million years ago and perhaps as early as 40 million years ago. The 

 ice accumulation climaxed 4 to 5 million years ago after which time 

 the ice front abruptly retreated to its present position. Gaseous 

 hydrocarbons were encountered in sediments in three of the four 

 holes drilled in the Ross Sea. Preliminary results indicate that the 

 gas is dominantly methane with significant traces of ethane and, in 

 one instance, ethylene. Traces of oil were also found in three sites 

 adjacent to the southeastern part of Australia near Tasmania. 



The Tasman Sea, south of Australia, was demonstrated to be 60 to 

 75 million years old, as previously predicted on the basis of 

 geophysical data. The Tasman Sea region, therefore, significantly 

 predates the breakup of Australia from Antarctica 50 million years 

 ago and the arrival of the southern continents at their present 

 positions. Drilling in other parts of the Pacific showed the geologic 

 youth of the Philippine Sea (60 million years old) and the Sea of 

 Japan (20 million years old). Evidence of major climatic oscillations 

 during the past million years was also detected in young sediments 

 from the Sea of Japan. 



Research programs conducted by the U.S. Geological Survey 

 (USGS) are concerned primarily with energy resources. Projects 

 involve the delineation of regional continental margin structure in 

 areas of potential gas and oil reserves, environmental research 

 leading to an improved understanding of the marine ecosystem and 

 of the changes that may result from resource development, studies of 

 geologic processes related to the accumulation of oil and placer 

 mineral deposits, earthquake hazards and the geochemical processes 

 involved in mineral development, and fundamental processes 

 governing the ecosystem in estuaries and along open coasts. 



Recent surveys along the Arctic coast of Alaska identified an 

 extensive, deep basin of sedimentary rocks in the southern Chuskchi 

 Sea; rocks and structures that extend west from Alaska's 

 petroliferous north slope were located beneath the northern 

 Chuskchi Sea. Between 70 and SOpercent of the shelf and slope areas 

 had favorable conditions for oil or natural gas; in the adjacent 

 Beaufort Sea, the entire area may be petroliferous. 



112 



