576 R. C. ALLEN AND L. P. BARRETT 



STRUCTURE OF THE LITTLE LAKE HILLS 



Rising to a height of possibly loo feet above a featureless fiat 

 sand plain near the station of Little Lake are two hills on which 

 there are many exposures of pre-Cambrian arkose, quartzite, .and 

 quartz slate with associated conglomerates. These hills present 

 today, in reference to the fluvio-glacial sand plains in which their 

 bases are buried, somewhat the same appearance that they seem 

 to have had near the close of pre-Cambrian time, when they were 

 monadnocks on a pre-Cambrian peneplain, for remnants of fiat 

 lying Paleozoic (Cambrian or Ordivician) limestone still cling to 

 their sides and summits. 



The eastern and larger hill is nearly a half-mile in diameter; 

 the western and smaller one is about three-eighths of a, mile long in 

 an E.-W. direction with a basal width of about one-eighth of a mile. 

 The exposures are most abundant on the north half of the east 

 hill, but on both hills there are a large number of pits and trenches 

 which were dug many years ago by prospectors whose diligence 

 deserved a better reward than this locality seems to have offered. 

 Aside from the red color of some of the quartz slate beds in the 

 upper series, iron-stained shear zones in the quartzite and arkose, 

 and an exposure at locality F (see figure) of about eighteen inches 

 of hematite occupying a lens-shaped cavity along a zone of thrust 

 faulting in massive quartzite, there appears no present evidence 

 of the attractiveness which these hills seem to have presented to 

 the early prospector for iron ore. 



The structure of the north side of the east hill is apparently 

 an anticline, the crest of which has been cut away by erosion, 

 thus exposing the arkose and associated conglomerate of the lower 

 (Gwinn) series flanked on the north, east, and west sides by con- 

 glomerate, quartzite, and quartz slate of the upper (Princeton) 

 series. This is the only complete structural feature which can be 

 determined from the available data. There is evidence in the 

 development of cleavage and schistose structures, shear zones and 

 faults of bo-th normal and thrust type, that general deformation 

 has been severe. Further evidence of the intensity of deformation 

 is afforded in the overturning of the formations, with consequent 

 apparent reversal in succession, in exposures at locality A at the 



