BETWEEN IRON-DOME AND CARBONATE FAULTS. 249 



Waterloo claim its continuation shows a slight upthrow to the west, so that 

 at some point south of that its movement must be null. 



South of California gulch. — Of the actual rock surface of the southern portion 

 of this area, which is deeply buried beneath thick deposits of Lake beds and 

 the superincumbent moraines of the Iowa glacier, nothing is as yet definitely 

 known. The outlines as given on the map must therefore be regarded as 

 theoretical deductions from the structure of the adjoining regions developed 

 by actual explorations. That a synclinal fold exists here is well proved, 

 and the probable slope of the rock surface beneath the Lake beds would cut 

 off the successive sedimentary formations approximately along the lines 

 represented on the map. 



In Iowa gulch the few prospect shafts were still in surface material. 

 The Black Cat shaft, on the ridge north of the gulch, had been sunk 530 

 feet through moraine material and underlying Lake beds. 



In Georgia gulch the developments of the Coon Valley shaft, where a 

 drill was supposed to have reached contact at 575 feet, show a thickness of 

 200 feet of Wash, 375 feet of Lake beds, and 75 feet of White Porphyry, 

 with the contact not yet reached at 650 feet. The Resumption shaft, near 

 this, found the same thicknesses of Wash and Lake beds, but had not reached 

 the porphyry. In the Zulu King (N-24) and Commercial Drummer 

 (U-1), northwest of this, near the top of the ridge overlooking California 

 gulch. White Porphyry was found at comparatively shallow depth im- 

 mediately under the Wash, showing that beneath Georgia gulch a bay once 

 existed in the original Arkansas lake. 



Proof of synclinal fold. — The intrusive body of Gray Porphyry between 

 White Porphyry and Blue Limestone comes to the surface on the banks of 

 Iowa and California gulches, adjoining Dome fault on the west, thus proving 

 a westward dip in the underlying formations ; in other words, that they 

 basin up to the eastward and that the Dome fault runs along or near the 

 axis of a shallow anticlinal fold. It has been reached after passing through 

 White Porphyry on the California gulch side by the Bank of France shaft, 

 in the angle of the Dome and California faults ; by the City Bank and Oro 

 City shafts, higher up the slope ; and by the Vining (N-19), near the fault 



