177 FER\rOR : CKOTiOGY AND COAL RESOURCES OF KOREA, C. P. 
lanunao and fragments of shale or of coaly matter, indicating the lapse 
of a slight interval between the deposition of the coal series (? in 
lagoons) and the resumption of the shallow fluviatile conditions under 
which the typical false-bedded sandstones must have been deposited. 
In the discussion of the Talchirs (page 1G8) it has already 
been pointed out that (ine-graiued argillaceous sandstones also occur 
at the base of the l^arakar series. In fact the Barakar period 
seems to have conunenced with a gradual shallowing of the deeper 
waters of the Talcliir lacustrine), leading to their conversion 
into river valleys. 
The rocks comprising the coal series or coal 
The coal series. , . 
horizons are : — 
(1) coal ; 
(2) every intermediate stage between coal and carbonaceous 
shale ; 
(3) several varieties of shale comparatively free from carbona- 
ceous matter, and often very micaceous ; 
(4) shaly sandstones or sandy shales composed of alternating 
layers of shale — carbonaceous or micaceous — and fine- 
grained sandstone, usually Very micaceous, and with the 
various layers thinning out lenticularly or displaying 
false-bedding on a small scale ; 
(5) micaceous sandstones, usually well-bedded or flaggy. 
The coal often occurs as the topmost stratum, resting either 
on shale or shaly sandstone, the latter passing down into the 
flaggy micaceous sandstone. But there is sometimes a small thick- 
ness of shale overlying the coal. In places the coal occurs alone, 
overlain and imderlain directly by sandstone, being then usually 
very thin. When more than one coal seam occurs in a section 
there may be a great number of alternations of carbonaceous, 
argillaceous, and arenaceous rocks. Further, the coal seams them- 
selves are frequently broken up by shaly or sandy partings. The 
total thickness of rocks in these coal horizons is very variable, 
sometimes only a few feet, more usually 10 to 20 feet, but some- 
times very much greater, the greatest thickness observed being at 
the Karar Khoh in the Kaoria Nala (Kurasia field), namely about 
92 feet (see page 205). The associated shales and sandstones are 
usually more important in the Kurasia field than in the Sanhat 
field, there being also a tendency for a greater thickness of coal 
at one horizon. A good idea of the composition of these coal 
