274 THE MAIIQUETTE IRON -BEARING DISTRICT. 



complicated folding of the beds, it was difficult to make tlie determinations 

 at all accm'ate, as the same layer is reproduced in exposure several times. 



Beginning- at the north and at the bottom of the exposures, the lime- 

 stone plunges under the novaculite with a dip of 50° to the south. In 

 passing toward the south, while the same layer, as has been said, may be 

 repeated b)- the folding, on the whole higher and higher members appear. 

 The whole is a part of an east-of-south-dipping stratum, which, however, is 

 itself bent into a number of secondary folds. If one sights along the axes 

 of the folds toward the west, he sees that the slate will rise above the Kona 

 dolomite, the same as it does where the two are in contact to the nt)rtli. 



The folding of the Wewe slate and Kona dolomite in this vicinity is 

 almost an ideal case, illustrating the types of folds and observations to 

 be made in districts of complex folding. The use of topography, tops of 

 anticlines, bottoms of synelines, and the pitch of one set of folds to obtain 

 the dips of the cross set are all shown.^ 



The movements of the Wewe slate have produced a cleavage — in cer- 

 tain places something of a schistose structure, and in the novaculitic layers, 

 as has been said, a breccia. The pseudo-conglomerate at the bottom of the 

 formation was at first supposed to be a true conglomerate, and was thought 

 to mark a possible unconformable break between the slates and the dolo- 

 mite (PI. VII, fig'. 2). The strata were, howevef, found to be strictly con- 

 formable, and the chert and novaculite fragments dynamic rather than 

 waterworn pebbles. Traced along the strike, the autoclastic rock gradually 

 passes into the continuous layers. It appears proliable that the fine sand at 

 the base was interstratified with calcareous layers, that the carbonate was 

 leached oiit and replaced by chert, and that when folded the rock was 

 broken. As further evidence that this rock is a pseudo-conglomerate, 

 the novaculites higher in the formation at many places have been broken 

 thi-ough and through in a similar manner and changed into breccias, 

 the fragments of which are cemented by secondary cherty quartz. In 

 the more argillaceous rocks a slaty cleavage has everywhere develoj^ed, 

 which sometimes passes into partial schistosity. These phenomena are 



' Principles of North American pre-Cambrian geology, liy C. R. Van Hise : Sixteenth Ann. Rept. 

 TJ. S. Geol. Survey, Part I, 1896, pp. 626-631. 



