SIBERIAN BASALTS 



791 



amounts of normative albite and anorthite, the almost negligible amount 

 of orthoclase, the approximately equal amounts of diopside and hy- 

 persthene, and the high magnetite and ilmenite molecules. 



Siberian Basalts 



In central Siberia is a very large, and as yet imperfectly known, area 

 of basaltic rocks, which, although not everywhere continuous, occur as 

 extensive horizontal sheets, forming either flows or intruded sills. The 

 name Siberian traps has been given to this complex by Eussian geologists. 

 The main and central areas are mapped by Ahlburg 31 (figure 2), but ac- 

 cording to Suess 32 and Backlund 33 they have a much wider extension than 









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fV# / 



rtf- 





4 q./ \ 







vk 7 / 



/ i y / r 



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\ Jf / 

















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Figure 2. — Sketch Map showing the main central Area of the Siberian Basalts 



(From Ahlburg.) 



shown by Ahlburg. Outliers occur northward to the Arctic Ocean, from 

 the mouth of the Yenisei eastward as far as the De Long and New Sibe- 

 rian Islands (possibly beyond) and inland nearly to Bering Sea. Suess 

 and Backlund comment on the similarities between these Siberian basalts 

 and those of the North Atlantic (Thulean) region and suggest — Back- 



31 J. Ahlburg : Zeits. prakt. Geol., vol. 21, 1913, p. 108, and figure 1. 



32 Suess : The face of the earth (English translation), vol. 3, 1908, pp. 20-38. 



33 H. G. Backlund: Mem. Acad. Sci. St. Petersburg, vol. 21, no. 6, 1910; and Acta 

 Acad. Abo., vol. 1, 1920. p. 1. 



