SECT. 2] 



INSOLUBLES 



301 



than that of quartz. These observations probably are related to the much 

 smaller size range of the clay mineral (less than 1 micron) and of atmospheric 

 and hydrospheric fractionation processes. One might expect the quartz to be 

 less dispersed on the sea floor, subsequent to fall-out, due to its larger size and 

 hence much smaller residence time in both the air and oceans. 



An independent line of evidence as to the continental origin of the illite 

 evolves from the work of Hurley, Hart, Pinson and Fairbairn (1959) who 

 found, from potassium-argon dating of surface Pacific illitic clays, various ages 

 up to hundreds of millions of years. This work clearly negates an authigenic 

 origin of illites. 



The longer cores from the Pacific show marked changes in both the quartz 

 and illite contents from modern to older strata (Fig. 4). Such curves, when 

 combined with appropriate age-dating techniques, may provide a paleo- 

 meteorological or paleoclimatic tool which may have recorded in the sediments 

 past climates and/or past air movements. 



Feldspar % = 0.51 quartz % + 0.32 



(J' = 0.045 

 N =12 

 r = 0.96 



7 



10 14 



% quartz 



2 6 



% quartz 



(a) 



(b) 



Fig. 3. (a) All samples from the Province of Hilly Topography in the eastern Pacific north 

 of 8°N, east of 170°W and more than 500 miles from the continent. 



(b) All samples containing detectable quartz and feldspar (phillipsite-free) from the 

 Province of Hilly Topography from 8°N to 18°S more than 500 miles from the 

 continent. 



Volcanic ash horizons have been of major importance as stratigraphic 

 indicators. For example, Bramlette and Bradley (1940) used sihcic volcanic ash 

 zones to establish a stratigraphy in Atlantic sediments. 



The correlation of ash beds with sources and a transport mechanism has 

 received some attention. The difficulties in such work stem from our insufficient 

 capability of predicting the dispersal patterns of dust. Further, quantitative 

 approaches to the relative contributions of volcanic materials to sediments are 

 hampered primarily because of the difficulty of recognizing degradation pro- 

 ducts resulting from chemical and physical changes in the original material. 



Mellis (1954) has suggested that certain ash horizons in Mediterranean cores 

 arose from activity of the Santorin eruptions. Kuenen (1950) and Neeb (1943) 

 noted ash from modern eruptions of Tambora and Oena Oena in Indonesia out 

 to distances of 300 km, which contributed up to 80% of the material in certain 

 deposits. 



