278 A. L. Leach—Glacial Drift near Amroth. 
VITI.—On « Gractat Drirr ar Marros, nEaR AmnorH. 
By A. L. Lzacu. 
NE mile and a half east of Amroth a small valley which opens on 
the coast of Carmarthen Bay at Marros shows drift deposits of 
much interest. The valley itself is noteworthy. Like several others 
in the vicinity it is deeply cut in comparison with its width; the 
gradient of the valley sides is as high as 1 in 2, and the depth below 
the bordering hills is not less than 300 feet. The stream, which now 
drains the valley, rises on Marros Mountain, barely 2 miles from 
the shore, and flows down the main dip-slope of the Coal-measures, 
which here are greatly disturbed by folds and faults. 
The pre-Glacial origin of the valley is suggested by its depth, and 
fully confirmed by the nature of the drifts, which cover the floor and 
are well displayed on the shore, where the sea has cut into these 
deposits and formed a vertical section, 200 feet long, extending from 
side to side of the valley. Other sections are shown in the banks of 
the stream, which by excavating a new channel through the drifts 
has cut down to the pre-Glacial rock-floor. But although the stream 
has reached the rock it does not. flow along the lowest part of the 
pre-Glacial valley ; it has cut a new channel in the rock several feet 
above the base of the drifts and, as will be shown later, its post- 
Glacial erosion may be estimated. The chief interest of this small 
valley arises from the exceptional clearness of the relation between 
the drifts and the valley-floor. The larger valleys to the west of 
Marros are choked with recent alluvial deposits, and their mouths 
are blocked by sand-dunes and storm-beaches, which, except in one 
case, completely hide any glacial deposits that may be present. 
The Marros Valley is excavated in shales and grits of the Coal- 
measures. A small anticlinal fold rises under the glacial gravel in 
the mouth of the valley, and probably a fault is concealed by the thick 
drift deposit. 
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Section of the Drifts at Marros, near Amroth: a, newer stony loam; 3, older stony 
loam; ¢, glacial gravel. Length of section 200 feet. The thickness of the 
drifts is exaggerated. 
The drift section shows at the bottom a stony loam composed of 
decayed local rocks, in which are embedded angular blocks and slabs 
derived from the slope of grits and shales against which it rests. 
Close to the west side of the valley this deposit is nearly 20 feet thick, 
but after it passes under the glacial gravel its base, being hidden by 
a storm-beach, cannot be seen, and the thickness shown in the cliff 
does not exceed 3 or 4 feet. The glacial gravel rests upon an wneven 
surface of this stony loam, except on the eastern side, where it rests 
