GEOGRAPHY, TOPOGRAPHY, AND GENERAL GEOLOGY. 21 
by assuming tension along the crests of anticlines, resulting in strike 
joints and faults. It may be pointed out that no considerable uplift 
of the arch necessarily precedes faulting of this kind, for the faulting 
may follow the tendency to uplift so closely that the two movements 
are nearly simultaneous. It is of interest in this connection to note 
that Huntington and Goldthwait have developed the fact that the 
relative vertical movements produced by the folds whose axes are 
parallel to the Hurricane fault were in opposite directions from those 
produced by subsequent faults. In the former case the west or Great 
Basin side was uplifted with reference to the east or High Plateau side, 
while in the subsequent faulting the Great Basin became the down- 
throw side, suggesting a drop of the anticline — that is, normal fault- 
ing consequent on the folding. 
SEQUENCE OF GEOLOGIC EVENTS. 
The principal features in the development of the present geological 
and physiographic features of the district have been in order as follows : 
(1) Deposition of Carboniferous limestone, with thin fragmental 
base, on basement unknown in this district. 
(2) A period of nondeposition, perhaps erosion, followed by deposi- 
tion of Cretaceous and perhaps some Jurassic sandstone with layers 
of shale, conglomerate, and limestone. 
(3) An erosion interval, followed by deposition of Eocene lime- 
stone and conglomerate in an inclosed basin. The conditions are 
principally those of shallow water, strong currents, and rapid changes 
through both Cretaceous and Tertiary times. 
(4) In early Miocene time intrusion of andesite laccoliths, princi- 
pally into the Carboniferous limestone, but also into the overlying 
Cretaceous, accompanied by tilting of all the formations away from 
the laccoliths, steeply near the laccoliths, less steeply farther away. 
Limestone and sandstone were metamorphosed near the contact. 
(5) Fissuring and faulting caused by cooling of laccoliths. 
(6) Immediate advent of ore-depositing solutions through fissures 
in the andesite, depositing iron ore in the andesite fissures and in the 
adjacent limestone and affecting other alterations. 
(7) Erosion, exposing the laccoliths and rings of sediments and 
ores around them. 
(8) Extrusion of late Miocene lavas over the entire area, except 
possibly some of the higher peaks of the exposed laccoliths, effecting 
a secondary concentration of the ores and further altering the under- 
lying rocks. 
(9) Further faulting. 
(10) Vigorous erosion, reexhuming the andesite cores and develop- 
ing the Pleistocene conglomerate and the Pleistocene and Recent 
mantle of stream, lake, and other alluvial deposits. 
