QUATERNARY. 195 
appears to have been in part washed into hollows, since with the loess it 
is locally 80 feet, 24 meters, deep, but it has not been sorted by wind. It 
is clearly of local origin and survives from an earlier epoch, characterized 
by climatic conditions favorable to decay. 
The Huang-t’u in the basin of Huang-t’u-chai is distinctly stratified, 
there being in the bluffs horizontal lines several feet apart, visible from a 
distance of 100 meters or so. They are not distinct lines of color, though 
they might appear as such if the surface were not covered with yellowish 
gray dust, but they come out as details of form in the sculpture of the 
cliff. This bedding was not observed in the loess of the higher slopes. 
Both the stratified and unstratified Huang-t’u exhibit vertical cleav- 
age. This structure occurs indifferently in the great mass filling the valley 
from top to bottom of sections more than 200 feet, 60 meters, deep and in 
the shallowest drifts on the mountain slopes, provided they are consolidated. 
It is poorly developed where the proportion of alluvial sand or gravel is 
large, and is wanting in eolian drifts from the latest dust storms. In the 
residual soil the structure resembles that of similar clays elsewhere, being 
of irregular fracture with a tendency to cave and produce steep or over- 
hanging facets, that wear back to slopes. 
In the basin of T’ai-yiian-fu we observed no peculiarities of the 
Huang-t’u especially worthy of note. The far-spreading plain, a surface 
of aggradation largely cultivated, afforded little opportunity to see sections, 
and we were unable to verify von Richthofen’s inference that the basin is 
partly filled by lake deposits, though this is quite possible in view of the 
upwarp across the valley of the Fén-ho below Ling-shi-hién. 
Between Ling-shi-hién and P’ing-yang-fu the Huang-t’u covers the 
uplands up to more than 1,500 feet, 450 meters, above the river. Under- 
lying strata of the Shan-si coal-measures are exposed in many ravines, 
but the slopes are buried in fine silt to depths that range from 100 feet, 30 
meters, to possibly 300 feet, g0 meters. The deposit is thickest next to 
the valleys, and is there interbedded with layers of coarse wash. Thus, 
north of Y6n-yi-ssi, at an altitude of 700 feet, 210 meters, above the town, 
there is a 30-foot, 9-meter, bed of pebbles, up to 5 centimeters in diameter. 
The bulk of the material appears to be loess, but in the sections seen along 
the road the true constitution is obscured by a coat of dust, and coarser 
sand and gravels may be present in larger proportions than one expects. 
Vertical cleavage is everywhere characteristic, as shown in Plate XXIX. 
About P’ing-yang-fu and thence southward the Huang-t’u is an alluvial 
deposit of the usual preponderant loess, with characteristic texture, and 
vertical structure, but horizontally bedded. Here and there occur layers 
of marl, in one case 30 feet, 9 meters, thick, overlain by Huang-t’u. Beds 
