298 ANNALS NEW YORK ACADEMY OF SCIENCES 



Spar (acid labf adotite) , augite, magnetite and biotite. Pyrite and olivine 

 are absent. A fine-grained type occurs on the edge of the sheet. The 

 shale adjacent to the diabase has undergone induration, crystallization, 

 and change of color. There are developed in the round nodules of chlorite 

 pseudomorphs after cordierite. In addition to the difference in grain 

 between the diabase of the Haycock sheet and the dikes of the Boyertown 

 hills, a difference owing to the greater size of the former intrusive mass, 

 the Haycock diabase possesses certain characteristics by which it is dis- 

 tinguished from the diabase of the Boyertown region. The most promi- 

 nent characteristic is the freshness of the constituents of the diabase of 

 the Haycock sheet; the diabase of the Boyertown hills has undergone 

 marked alteration by suassuritization and chloritization, which has ob- 

 scured the ophitic texture and dulled the rock and changed the color. 

 Pyrite is absent in Haycock diabase, but is abundant in the diabase of 

 the Boyertown hills. Stratigraphic relations point to a difference in age 

 of the two diabases. Field relations prove the Triassic age of the Hay- 

 cock sheet which has invaded Upper Triassic sediments. The diabase 

 of the Boyertown hills nowhere penetrates to a horizon younger than the 

 Precambrian. Therefore the alteration prevalent in the diabase of the 

 Boyertown hills may be explained by their Precambrian age and the 

 greater metamorphism they have undergone. 



Professor Grabau stated that the three important oil-bearing forma- 

 tions which he has studied in detail are the Trenton limestone, the 

 Onondaga (Corniferous) limestone, and the Upper Devonie oil sands 

 of Pennsylvania. In all cases it is shown that these formations grade 

 laterally into black shales of sapropeltic origin, these shales being the 

 source of the oil. Lateral migration along the bedding planes has re- 

 sulted in the accumulation of the oil in the more porous limestones or 

 sandstones in which they are found today. The beds which have pro- 

 duced the oils are the Utica shale .(in its broadest sense), the Marcellus, 

 and the Ohio shales. The relation of the Utica-Trenton and of the Ohio- 

 Portage relation is an interfingering one. The lower two shales are 

 sapropelites ; the upper m&re nearly a humulith, though having some 

 sapropelitic admixtures. The significance of this relationship in the 

 determination of oil-bearing horizons is apparent. 



'rhe Section then adjourned. 



Chester A. Eeeds, 



Secretary. 



