GEOLOGICAL RECORD OX THE OCEAN FLOOR 139 



Late Pleistocene climatic development in peat bogs hav^e been 

 correlated by interstratified ash layers from the Andean volcanoes. 

 Correns (1937), in his work on equatorial Atlantic sediments, 

 noted the variability in the volcanic components, and in the 

 Mediterranean a great deal of interest has been devoted by 

 Mellis, Pettersson, and Norin (1958) to identification of observed 

 ash layers in the sediments with known historic or prehistoric 

 volcanic events. The first and so far perhaps most successful 

 attempt at oceanwide correlation of ash layers in long sediment 

 sequences was made by Bramlette and Bradley (1942) in the cores 

 raised by Piggot between Newfoundland and Ireland (Fig. 5). 

 These results offer a powerful tool for correlation of the numerous 

 long cores which since have been raised in the North i\tlantic, 

 and for reconstruction of the volcanic history of the whole region. 



One of the most dramatic discoveries of this kind is the recent 

 finding by Worzel (1959) of extensive ash beds in sediment cores 

 near the South American coast (Fig. 6) all the way from Peru to 

 Mexico. In their preliminary description of these strata, Ewing, 

 Heezen, and Ericson (1959) interpret them as one continuous unit, 

 which would represent a single gigantic eruption. One would, 

 however, under these conditions expect to encounter the layer also 

 in the more slowly accumulating sediments further out in the 

 equatorial Pacific, reworked and spread vertically by bottom 

 organisms (Fig. 7) and perhaps altered to montmorillonite but 

 still mineralogically discernible. In these cores, including one from 

 the Galapagos area, not far away from the Worzel ash in the Bight 

 of Panama, however, several minor concentrations of unaltered 

 ash of different types, and of montmorillonite are found, but 

 nothing of the dimensions observed near the coast. It appears, 

 therefore, that at the present time caution should be observed in 

 the correlation of the coastal ash layers, that might well be derived 

 from a series of eruptions from different volcanoes in the Cordillera. 



While the volcanic dust appears as spikes in the sedimentary 

 record, there is a fluctuating continuum of airborne detritus carried 

 out over the oceans (Fig. 8) and deposited there, especially from 

 the arid lands of the world. This dust has quite a varied mineral 

 composition. One of the major components which is easily deter- 



