156 KUMMEL AND WELLER LIMESTONES OF KITTATINNY VALLEY 



marked, is distinctly oblique to tlie under] 3dng beds. The fragments 

 in the lower la3'ers of the conglomerate are coarse and angular, sur- 

 rounded by a matrix of smaller fragments of the same sort, and have 

 evidently undergone but little transportation and sorting. In the upper 

 beds the fragments are smaller, better rounded, and the matrix carries 

 crinoid .stems and other obscure fossils. Above the conglomerate is 

 found the typical Trenton limestone, through which are scattered occa- 

 sional Kittatinny limestone pebbles. In other localities the dips of 

 closely adjoining beds of Trenton and Kittatinny formations are not 

 more discordant than might be expected in conformable formations 

 which have been more or less closely folded. 



Trenton Limestone 



character and thickness 



The. Trenton limestone proper rests either directl}' on the Kittatinny 

 limestone or on the basal conglomerate. It is a dark blue or black, 

 non-magnesian limestone, in massive beds, generally weathering into 

 thin, knott}^ irregular layers, a few of which are minutel}'^ crystalline. 

 Some of these layers contain as high as 95 per cent carbonate of lime. 

 Intercalated with the i)urer limestones are more shal}' beds, and the 

 whole formation grades into the overlying clayey, micaceous, slate, and 

 sandstone formation through a series of calcareous shales, which are 

 sparingly fossiliferous and commonly concealed by glacial drift or wash 

 from the harder and toj)ogra})hically higlter layers. It is this calcareous 

 shale which forms the '' cement rock " of the Lehigh and Phillipsburg 

 Portland Cement regions. These calcareous shales, with the occasional 

 thin bands of limestone which occur in them, are classed with the un- 

 derlying fossiliferous limestones, rather than with the overlying argilla- 

 ceous slates, although there is no sharp line of demarkation between 

 them. 



In the northern and central part of the Kittatinny valley the thick- 

 ness of the Trenton is about lo5 feet, but it increases toward the south- 

 west, being 300 feet or more near the Delaware and apparently something 

 more than' that in the Lehigh region, Pennsylvania. The increase in 

 thickness is due apparently to the increase in the thickness of the cal- 

 careous shales, the cement rock at the top, rather than of the purer, 

 massive, fossiliferous limestones below. 



CHEMICAL COMPOSITION 



The Trenton limestones are not magnesian, as is the great mass of the 

 Kittatinny formation. The purest layers contain 52 to 55 per cent of 



