Till': jjKrnr.Lio tkoikiii. 541 



iittU^ folds ncarh' parnllcl to their axes. In cll'cct, tlicrctorc, tlic j:is|icr 

 oiitcro|is on this northern slope show a paralh'l handinj;- strikint^' nortli\vt\st. 

 On the top ol tlie liill, ho\ve\cr, the true strike is clearly hroii^ht out on 

 the vertical cross joints. 



Tlie Goodrich (|Hart/.itc, which is nui(di niori^ massive and heavily 

 bedded than the Nej^'aunee I'orniation, yiel<le<| to the intense compression 

 1)\ dilVei-ential movements of one hed on another, and doiditless also l)\' 

 thickeninf^'. The effects of the movement of hed on lieil are clearly and 

 strikiiii^'ly shown at nmnerous points in the horseshoe, perhaps particularly 

 wvW in the small open pit east of the Ml\ shall. Ilere the inili\idual 

 (piartzite heds, iVom I foot upward in thickness, are separateil hy paralKd 

 selvayes of g'voimd-up (piartzitic material, \ar\ini;' in thickness nsuallv 

 froin 2 to 4 inches. In the case of one the measured thickness was I 1 

 inches. These selvag'es, known locally as a A^ariety of "soapi'ock," show 

 frequently a vertical pressure (dt'ava;4e. 



M.ij. T. B. Brooks sliows, on his lar<;e-scale ma]) of lie])nl)lic Mountain* 

 and vicinity, tlu^ c()urs(f of a prohabh^ lault cuttinji- diaj^onally across tho 

 .syncliiu' in a nortlieasterl\ direction alon<;- the I'iver in sec. 7, north of 

 the horseshoe. Brooks was led to infer the existence of this fault from the 

 fact that he i-ei^'arded the diorites as re<iularly interheddcd and continuous 

 members of the stratified series, and from his failure to recognize the 

 uncoidbrmity at the base of the Goodi'ich (lua-rtzite. 



On the northeast side of tin* syncdine diorites outcrops a shoit distance 

 north of tlui Milwaukee an<l NortluM-n b'aili-oad water tank, on the (^ast sid(! 

 of the river, and lies directly in the line of strike ol' jaspers that are widl 

 exposed a, few hunilrecl fei^t away on the west bank. 



On the southwest sid(^ of tlut syn(din(^, north of the horseshoe, the 

 Tjower Abn-quette rocks whi(di lie below the Goodrich (luartzite on the east 

 sid(^ of the river would, if prolonj^'ed alonj^- tin* strike^ be carried directly 

 ajiainst j^-i'anites whicdi occupy the west bank, west oi' the West IJepidilic 



'Geol.Siirv. of Michigiiii, AtliiH aoooiiiimiiyiiif; niporlH om llpiior rdiiiiiHiilii, 1*1. VI, by 'P. It. HiooUh, 

 1869-1873. 



