LOWER CRETACEOUS. 629 



The upper shales (A) are generally arenaceous and interstratified with sand- 

 stones from 3 to 6 inches thick. A bed of sandstone 30 feet thick occurs 70 feet 

 above the base, and the lowest shales are interstratified with reddish-weathering, 

 grayish-brown dolomite, which constitutes the chief part of the mass and seems to 

 form a passage to the underlying conglomerates. The shales have yielded but one 

 recognized fossil, " Inoceramus problematicus.'"' 



The conglomerates (B) include for the most part well-rounded pebbles, in some 

 layers several inches in diameter, derived from the more or less crystalline pre- 

 Cretaceous rocks; rounded shaly fragments of the next underlying Cretaceous are 

 also found, indicating slight erosion, but no true unconformity, during the deposition 

 of the conglomerate. Gray and yellow sandstones are interbedded and the upper 

 part of the conglomerate is dolomitic. 



Thie lower shales and sandstones, at the base of which the anthracite coal is found, consist 

 of blackish or gray shales, interbedded with gray or yellowish-gray sandstones and numerous 

 layers composed of sandy argillaceous material, intermediate in character between shale and 

 sandstone. The bedding is generally regular and certaia zones are characterized by large 

 calcareous nodules, generally lenticular, and occasionally several feet in diameter or even 

 coalescing to form sheets of calcareous matter. Layers so coarse as to be called conglomerates 

 scarcely occur. The beds immediately underlying the conglomerates of subdivision B are 

 generally gray shales, very regular in their bedding, and quite hard. Below these is a con- 

 siderable thickness of strata in which shaly beds usually preponderate, while toward the base 

 of the subdivision sandstones are more important. The lowest beds are of interest as being 

 those in association with * * * the coal. * * * 



Subdivision C rests on a series of volcanic rocks constituting subdivision D, which appar- 

 ently forms a member of the same formation. The upper surface of the agglomerate and ash 

 rocks of D must, however, have been an irregular one, and to its undulations the lower beds of 

 C more or less closely conform. The appearance at the junction of subdivisions C and D is 

 therefore that of an unconformity more or less marked. * * * Tjiig partial unconformity 

 is, however, believed to be essentially unimportant and only such as might be anticipated at 

 the junction of two classes of deposits so dissimilar. * * * The occurrence of fossils identi- 

 cal with those of subdivision C in beds below the volcanic horizon, with the inclusion of marine 

 forms in some parts of the upper portion of the rocks of volcanic origin (at points on the east 

 side of AUiford Bay), serve to show the continuity of the conditions of deposit. 



The passage beds have been observed in a number of localities to be coarse feldspathie or 

 tufaceous sandstones, generally pale in color and formed apparently by the rearrangement of 

 the still unconsolidated materials of the upper beds of D. These vary in thickness but are 

 generally associated with black carbonaceous argillites, which are sometimes shaly and at the 

 Cowffitz mine hold the seam of anthracite coal. 



******* ** 



[The agglomerates which constitute subdivision D] are almost exclusively of volcanic origin, 

 though some layers show traces of water action in the rounding of fragments. Some beds may 

 have been flows of molten matter, but most are of a fragmental character, either agglomerates 

 or tufaceous sandstones, of greenish, grayish, brown, or purple tints. * * * q^g material 

 is almost everywhere predominantly feldspathie, and some specimens resemble typical 

 porphyrite of rather coarse grain. At the east side of the point north of AUiford Bay, hard 

 dark tufaceous sandstones are found graduating into agglomerates, some of which, however 

 have their fragments so well rounded as to be more appropriately designated conglomerates. 



"■I. labiatus. — T. W. Stanton. 



