DIFFICULTIES OF CORRELATION. 389 



Northern Ann Synclinal. — Southwest of the Genesee anticlinal there is a 

 broad synclinal of younger formations, extending from the Mormon 

 canyon of Indian creek to nearly three miles northeast of mount Jura. 

 The best exposures of the strata it contains, besides those of mount Jura, 

 are to be found in the eastern branches of the northern arm, especially 

 in the various gulches of foreman ravine. 



The detailed, arrangement of the strata within the synclinal is not easily 

 discerned. This is due chiefly to two causes: (1) the presence of a large 

 mass of overturned Jurassic strata, which not only fails clearly to partake 

 of the synclinal structure hut appears by its unconformity to cover up 

 other strata the repetition of which might he recognized ; and ( 2) except- 

 ing the Jurassic strata, the formations exposed within the synclinal are 

 poor in fossils, so that their correlation is a matter of considerable diffi- 

 culty. 



The central sandstone of the Foreman beds is well exposed in Foreman 

 ravine, and bounded on both sides by slates which contain occasionally 

 masses of conglomerate composed chiefly of quartz pebbles. The simi- 

 larity in the general character of the two bodies of slates adjoining the 

 central sandstone on opposite sides, taken in connection with the re- 

 currence at corresponding positions within them of rather peculiar con- 

 glomerates, tends strongly to indicate that they are the same formation 

 with synclinal connection beneath the central sandstone, but within the 

 Foreman beds. In the section (figure 1) the place of the central sand- 

 stone in the middle of the synclinal is occupied by an eruptive. 

 Although the Foreman beds appear to have been overturned and the 

 synclinal closed, so that for the most part the dip is southwestward, 

 there is a large portion of them near the northern end of mount Jura 

 that dip northeastward, and it is possible that a part of the original 

 open synclinal yet remains in that protected locality. A few fossil plants 

 have been found in a slaty portion of the Foreman beds. They are re- 

 garded by Professor Fontaine as certainly Mesozoic and most probably 

 Rhsetic in age. A favorable opportunity has not yet occurred to search 

 for them in all portions of the slates. 



The Ilosselkus limestone on the northeastern side of the synclinal is 

 covered up through a huge portion of its extent by the eruptives ad- 

 joining the Foreman beds. It is. however, well exposed in this position 

 ;it the old Lime-kiln on the northern slope of Genesee valley. 



It lias been recognized in I he southwestern a no of the synclinal, at ;i n 

 elevation of 1,800 feet on the slope of Grizzly mountain (see figure L-), 



aboul two miles southwest of Ilosselkus. where it is evident that ;i shorl 



distance further northward it must be concealed from view beneath the 



•Inra. 



