210 W. M. DAVIS NOMENCLATURE OF SURFACE FORMS 



In Scotland the abrupt southward descent from the crystalline highlands 

 to the worn-down stratified rocks of the central lowlands is made by what 

 seems to be a maturely dissected and strongly glaciated resequent fault- 

 line scarp, developed in a second cycle by renewed erosion on a previously 

 faulted and subdued mass. The long scarp on the northwest side of 

 Newfoundland, above mentioned as thought by Twenhofel to be a fault- 

 scarp, is possibly — or probably — a fault-line scarp. 



Several submature resequent fault -line scarps with eastward aspect are 

 crossed by the Mohawk valley in eastern New York, and have receive' 1 

 general study from Darton ('95). The scarp at Little Falls has been 

 described in detail by Cushing ( '05, 71-) ; others of diverse aspect far- 

 ther east near Saratoga by Miller ('11, 38-). A long and strong 

 resequent scarp, with southeastward aspect, forms the border of the 

 crystalline highlands toward the red sandstone lowlands in northern 

 New Jersey; it is described by Kummel ( '98, 110) as a geological bound- 

 ary rather than as a topographical feature. The eastern border of the 

 Connecticut valley lowlands in Connecticut and Massachusetts is a west- 

 facing scarp of the same nature, but more irregular in plan; it was 

 worked out by Griswold and is described in my report on the Triassic 

 formation of that district ('98, 122) ; the trap ridges of the same low- 

 land in Connecticut are repeatedly terminated by oblique resequent or 

 obsequent fault-line scarps, often too young to have their slopes com- 

 pletely graded, while in the already old, worn-down areas of weak sand- 

 stones the same faults are nearly or wholly obliterated ( '89, 68 ; '98, 89). 

 A remarkably good example of a maturely dissected obsequent scarp, now 

 worn a mile or more back from its fault line, runs transverse to the 

 dominating structural trends across the boundary between the Appala- 

 chian ridges and the Cumberland plateau in northern Tennessee; it is 

 well represented on the Briceville folio of the United States Geological 

 Survey. Several other obsequent fault-line scarps have lately been de- 

 scribed by Paige for central Texas in the Llano-Burnet folio. Subse- 

 quent fault-line valleys and obliterated fault scarps are repeatedly illus- 

 trated in the Appalachians of Virginia and Tennessee. 



The Hurricane ledge in the plateaus of northern Arizona north of 

 the Colorado canyon is an exceptionally fine young, west-facing rese- 

 quent fault-line scarp ; it was described as a young fault scarp by Dutton 

 ('85, 112-), but its resequent nature seems to be well established by a 

 lava flow that T found in 1902 to lie across the line of the obliterated 

 scarp of first faulting, protecting a local area of weak clays which have 

 elsewhere been worn away on the west of the fault line, leaving the re- 

 sistant limestones in bold relief on the east side (a, '03, 26-; '12, 171). 



