CLAYS OF CRETACEOUS FORMATION. 181 



cross-bedded, and this, together with the irregularity of the "feld- 

 spar" lenses, indicates that the deposit was made in rapidly mov- 

 ing water, where shifting currents- brought about constantly re- 

 curring conditions of deposition, erosion and re-deposition. 



It has been stated 1 that the "feldspar" beds are entirely un- 

 stratified, and that in this respect they are in marked contrast to 

 the other beds of the Raritan. It is true that in these lenses there 

 is no stratification or lamination of such a nature as to- separate 

 the quartz pebbles from the decomposed feldspar masses. The 

 two are most intimately mingled without a trace of the alternation 

 of clay seams and sand layers, which is sometimes seen in other 

 portions of the Cretaceous. Nevertheless, there are definite, 

 though not always obtrusive, lines of stratification in the "feld- 

 spar" lenses, and there is plain evidence of its deposition in water. 

 (Plate XX, particularly Fig. i.) 



As was noted above, the quartz pebbles are somewhat rounded, 

 and hence have suffered at least a moderate amount of wear dur- 

 ing transportation by streams or waves, The clayey or kaolinized 

 material is now for the most part so^ soft that it is difficult to 

 imagine how it could have been transported any distance in its 

 present condition along with the hard quartz without complete 

 disintegration. This difficulty is met, if it be assumed that the 

 alteration of the feldspar pebbles to- the clay masses has taken 

 place subsequent to> their deposition. The pebble-like form and 

 incomplete alteration of a portion of them accords with this as- 

 sumption, but the irregular shape and the manner in which much 

 of the clayey material surrounds the quartz pebbles are apparently 

 inconsistent with this hypothesis. It must be borne in mind, how- 

 ever, that, as the feldspar changes to* kaolinite, water is absorbed 

 and there is some increase in volume. This swelling may account 

 in part for the irregular outlines of the clay particles. To some 

 extent, also, settling of the beds since deposition may have 

 squeezed the clayey material around and between the quartz peb- 

 bles, but these explanations do- not seem wholly adequate. If the 

 material were derived from a partially decomposed rock composed 

 of quartz and large feldspar crystals, it may be assumed that some 



Report on the Clays of New Jersey, 1878, p. 62. 



