48 



5. R. CAP PS 



An examination of this section shows that although the elKpsoidal 

 flows form the larger proportion of the series, they are interbedded 

 with some more massive diabase beds. At intervals, however, 

 the extrusive rocks are seen to be interrupted by slates and gray- 

 wackes, the sedimentary beds becoming thicker and more fre- 

 quent as the top of the greenstone series is approached. The 

 strike and dip of adjoining lavas and sediments is the same, and it 



_«pp^^ 





Fig. 3. — Ellipsoidal lavas. The forms are ellipsoidal in cross-section, but in plan 

 are long uneven bodies characterized by bulbous portions separated by constrictions. 

 Photo, by S. Paige. 



is evident that clastic sediments were deposited at intervals between 

 the outpouring of the lava flows (Fig. 4). In a large number of 

 observations on slate or slate-graywacke beds interbedded with 

 ellipsoidal greenstones, no single case was found in which there 

 was a discordance in bedding between the sediments and the lavas. 

 Furthermore, in the cracks between the ellipsoids of the lower part 

 of a flow and in the smaller cooling cracks within the individual 

 ellipsoids there were frequently seen thin vein-like layers of a black, 

 shaly material which proved to be of the same character as the under- 



