—_ 
HUNTINGTON AND GOLDTHWAIT: THE HURRICANE FAULT. 221 
parts of anticlinal folds appear to be shoved away from the old land, and 
the plications now stand in unsymmetrical attitudes. In the Plateau 
province most of the flexing is monoclinal and of far simpler character 
than in the Appalachians. As these displacements involve but little 
horizontal compression, it has generally been assumed that they are due 
to the action of vertical forces by which one block was merely raised 
above or depressed below another (Gilbert, b, p. 86). In the Toquer- 
ville area and northward, however, we have a small district which has 
evidently been subjected to tangential pressure. The folds thus pro- 
duced are of the true Appalachian type, and at Kanarra are thrust over 
one another on a small scale, just as is the case in certain parts of the 
eastern mountains. Both in the Kast and in the West the direction of 
movement was such as to incline the tops of the anticlines away from 
the neighboring old land. South of the Pine Valley mountains these 
true folds of the Plateau province flatten out into monoclinal flexures. 
The query arises whether the monoclinal flexing of the Plateau province 
as a whole may not be a phase of a close folding of the Appalachian type, 
where for some reason most of the strata were affected but slightly. 
The manner in which the folds of the Toquerville region are intensified 
immediately east of the great lava mass of the Pine Valley mountains 
and bend around parallel to it is certainly remarkable. The mind at 
once attempts to formulate some causal relation, but that would be 
going farther than is warranted by our present knowledge. 
Gilbert (a, p. 62) has suggested that the faults of the Basin Range 
and Plateau provinces are the superficial expression of a deep-seated 
structure such as that of the Appalachians. Otherwise expressed, his 
hypothesis is that far below the surface there was great tangential pres- 
sure which forced the lower part uf the crust- into plications of the 
Appalachian type. The superficial layers, however, were not so folded, 
but were raised ‘and broken into blocks, as a sheet of ice may be broken 
by a wave that passes under it. This hypothesis seems to agree with 
all the known facts, including the new ones found in the Toquerville 
region. In Gilbert’s discussion he has shown (a, p. 59), as has also 
King (a, p. 744), that the Tertiary faults of the Basin Range and Plateau 
provinces follow the same lines as the plications of an earlier Jurassic 
upheaval. He has not, however, distinguished between the folding and 
flexing which took place in the early Tertiary on the one hand, and the 
periods of faulting which we shall later show to have occurred at the 
middle and end of thatera. If Gilbert’s hypothesis is correct, the strata 
that were deeply buried at the time when the earth’s crust was dis- 
