152 KUMMEL AND WELLER — LIMESTONES OF KITTATINNY VALLEY 



Contrasted with these there are several hundred feet of thin beds in the 

 upper part of the formation in which bands of limestone an inch in 

 thickness are separated by thin partings of greenish shale or by equally 

 thin layers of sandstone. Some layers contain much chert, both in the 

 form of nodular masses and as lenses a foot or less in thickness and 

 several rods in diameter. Some beds are minutel}'' cr3''stalline, some of 

 so dense and fine a texture that no grains nor crystals are visible ma- 

 croscopically, and some of the lower beds are oolitic. At a number of 

 points beds of almost pure limestone, alternating with the dolomitic 

 laj'^ers, occur near the top of the formation as exposed. Owing to a slight 

 unconformity, however, between this formation and the succeeding one, 

 the top is a variable horizon. 



The thickness of the Kittatinn}^ limestone is probabl}^ about 2,700 to 

 3,000 feet, although owing to folds and faults no absolutely reliable esti- 

 mates can be made ; but the figures obtained are not discordant with 

 estimates made in other states. 



CHEMICAL COMPOSITION 



Many analyses* of this limestone have been made by the New Jersey 

 Geological Survey at various times, so that its chemical composition is 

 well known. Nearly all the analyses, which are of s})ecimens from 

 widely scattered localities and different horizons, contain a large amount 

 of magnesia, whence the name magnesian limestone, applied by Doctor 

 Cook. Thirty-nine analyses showed the composition to vary within the 

 following limits: 



SiOj (silicic acid and quartz) 1.8 to 15.0 per cent. 



^j^'q^} 0.6 to 8.4 per cent. 



CaO 23.6 to 32.4 per cent. 



MgO 14.6 to 21.7 per cent. 



In the upper part of the formation a few thin layers of a purer lime- 

 stone, with 90 per cent or more of carbonate of lime, alternate with the 

 dolomite. 



FAUNA OF THE KITTATINSY LIMESTONE 



The calcareous sandstones forming the top of the Hardiston quartzite 

 pass insensibly into the lower arenaceous limestone of the Kittatinny 

 formation, but the Lower Cambrian fauna of the quartzite has not been 

 recognized in the Kittatinny limestone. The age of the beginning of 

 the continuous Hardiston-Kittatinny sedimentation may be definitely 

 fixed as Lower Cambrian. 



*As the analyses were usually made for economic purposes the l.)etter layers were probably 

 chosen and tlje markedly impure shaly or sandy layers rejected. 



