398 JOHNS : FAULTS IN THE SETTLE- MALHAM AREA. 
a wide area, the constancy of its relation to other well-marked 
faunal horizons and any lithological changes, and its deter- 
mination in the field. The line adopted fulfils each of these 
conditions. It has been mapped over a wide area in N.W. 
Yorks.; it always occupies the same relative position in the 
faunal sequence. It is associated with strong grey limestones 
that weather into well-marked scars, and succeed softer, purer 
limestone. The faunal characteristics can, when once deter- 
mined, be easily recognised in the field. Coming in abruptly 
as it does, after a series of relatively unfossiliferous beds, the 
new fauna, with its Giganteid producti and easily distinguished 
Dibunophyllid corals, can always be picked up if clear sections 
are available. 
The Gordale Faults. 
In the ascent of Gordale the most striking feature is the 
manner in which the great thickness of apparently unfossiliferous 
limestone is succeeded at the very top by a thin band crowded 
with large Producti and corals. This fossiliferous bed can be 
found on both sides if one works back a little. Sometimes it 
remains as isolated patches, forming outliers of Upper Visean 
beds, where denudation has removed the rest. Giganteid pro- 
ducti, Dihunophyllids, Carcinophyllids, Cyathophyllum Murchi- 
soni, and an occasional Cyrtina septosa make it clear that we have 
here the main entrance of the Upper Visean fauna. When 
the level of patches of these beds on opposite sides of Gordale 
is compared, there appears to be a displacement with the down- 
throw on the western side. The difference in level is not much, 
perhaps 10 feet is the extent. At the lower end of the gorge, 
where one has in ascending to leave the stream bed and climb 
up the talus on the left side, the actual fault can be seen, and 
the displacement measured. The downthrow here is again to 
the west, and the actual displacement is about 21 feet. Starting 
at the top, or northern end of the gorge, the stream flows south 
for about a quarter of a mile, then bends round to the S.S.E., 
in which direction it runs for half a mile. It is then that a sharp 
turn in a S.W. direction is taken for tlie stream to flow over 
the accumulation of calcareous tufa which blocks the entrance 
