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University of California Publications in Geology [Vol.8 



District to the monzonite laccolith in which, or close to which, they 

 occur. A great body of sediments consisting chiefly of quartzite and 

 sandstone, separated by several formations of limestone and shale, 

 has been folded into an open syncline and invaded by a comparatively 

 small laccolith of monzonite acompanied by sills and other apophyses. 

 The sedimentary rocks, known as the Bingham quartzite, have an 

 exposed thickness of about 10,000 feet and are referred to the Upper 

 Carboniferous; but neither the bottom nor top is known. The axis of 



Bingham Limestone Monzonite 

 quartzite formations laccolith 



Fig. 2. Sketch, after Keith and Boutwell, showing the relation of the in- 

 trusive monzonite to the syncline of the Bingham quartzite. 



the syncline pitches to the northwest and the laccolith lies to the 

 southwest of it, having been injected into the lower part of the sedi- 

 mentary series. The general structural relations are shown in the 

 accompanying diagram, figure 2, adapted from the geological map 

 which accompanies Keith's and Boutwell 's papers as plate 1. In 

 form the laccolith is irregular and large parts of the roof have sunk 

 into it, appearing now at the erosional surface as inclusions. It is 

 not known whether the syncline was developed before, or after, or at 

 the time of the intrusion. The metamorphism of the rocks encasing 

 the laccolith is manifested chiefly as marmorization and silicification 

 of the limestone and silicification of the quartzite. The ore deposits 

 fall into three classes : 



