. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. ly inclined one and, moreover, was possessed of notable irregu-larities of surface. The other exposed contacts of the amygdaloid and shale, which arelocated in the spring section, near South Britain, are clearly fault contacts, and their consider-ation will be deferred until thedeformation of the area is treated(see Chapter IV). One character-istic of the amygdaloid at thislocality should, however, be men-tioned here. By referenc
. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. ly inclined one and, moreover, was possessed of notable irregu-larities of surface. The other exposed contacts of the amygdaloid and shale, which arelocated in the spring section, near South Britain, are clearly fault contacts, and their consider-ation will be deferred until thedeformation of the area is treated(see Chapter IV). One character-istic of the amygdaloid at thislocality should, however, be men-tioned here. By reference to thesketch map of the area (fig. 27, ), it will be seen that the red shalehere has outcrops in the shape ofan acute triangle or wedge, theapex of which is exposed in the stream bed. The belt of amygdaloid,which is in contact with the shale upon the north, like that formingthe cliff wall to the southeast, can be shown to be separated from theshale by a fault, as will be fully explained in the sequel (p. 8t)). Thenorthern belt of basalt continues, however, to outcrop to the east-ward in the stream bed, and it is specimens of this basalt which will. Fig. 14.—Section across the contact of anteriorshale on the amygdaloidal basalt near RedSpring (locality a. fig. 13). 6, basalt; I, .shule;stippled area, cover. HOBBs.] CONTACTS OF MAIN BASALT. 53 now be considered. They were taken in the bed of the stream only afew feet above the apex of the wedge of shale. In them we find theusual characters of the anterior basalt sheet, there being numerousamjgdules filled with calcite and chlorite, although the rock is lessdecomposed than the normal rock. The special feature which distin-guishes these specimens from all others which I have observed is thatnear their upper surface (the uppermost inch or so of rock in theexposure) the coarse vesicles are filled not with infiltrated minerals,as is usual, but with the shale itself, which it would seem must havehere been deposited or washed in
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