Reports and Proceedings — Geological Society of London. 329 



extensive plateau of tlie Dombes, east and north of Lyons, com- 

 posed of marine marl overlain by the characteristic conglomerat 

 ferrugineux, which some French geologists still regard as pre- 

 Olacial and others as Quaternary, but which is typical Decken- 

 schotter, and in the full acceptation of the term an alluvion des 

 plateaux. The deposits thus described afford proof of the existence, 

 in Upper Pliocene times, of an extensive alluvial cone about 

 100 miles in length, which reached from Lausanne (probably even 

 from the base of the Alps) to Lyons, and was formed by the waters 

 of the retreating Khone and Arve glaciers on a Molasse-and-marl 

 plateau, the altitude of which above sea-level was 800 metres near 

 Lausanne and 300 metres near Lyons. 



From this concurrent evidence in Northern Switzerland and in 

 the Rhone Valley, the author is led to conclude — 



(1) That at the time of the deposition of those alluvial cones, the 

 principal Subalpine valleys and lake-basins could not as yet have 

 existed in their present form or depth, and must have been from 

 100 to 200 and 400 metres higher ; and 



(2) That the Subalpine valleys were eroded to their present depth 

 in the course of the inter-Glacial Period — now recognized to have 

 been of very long duration — between the Pliocene and the Middle 

 Pleistocene (or maximum) glaciations, and that the Subalpine lake- 

 basins were formed in the same period by the contemporaneous 

 action of fluviatile erosion and of a zonal settling along the base 

 of the Alps after these had been raised by horizontal pressure. 



2. " Overthrusts and other Disturbances in the Braysdown 

 Colliery (Somerset), and the Bearing of these Phenomena upon the 

 Effects of Overthrust Faults in the Somerset Coalfield in general." 

 By Frederick Anthony Steart, Esq. (Communicated by Horace B. 

 Woodward, Esq., F.R.S., F.G.S.) 



This coalfield, although covered by comparatively undisturbed 

 Secondary rocks, is in part the most disturbed and contorted of 

 those known and worked in the United Kingdom. It is seldom, in 

 some parts of it, that one sees 200 yards of coal without a fault 

 or other disturbance. The ' Radstock Seams ' of the Upper Coal- 

 measures at Eadstock are traversed by a huge ' overlap fault,' 

 which thrusts them forward for a great distance : this runs nearly 

 east and west, and has parallel to it two smaller overthrusts. In 

 one of them the coal at first dips towards the thrust, then it thickens 

 from 2 to 6 or 8 feet, next it becomes inverted, and eventually 

 regains its former character. The continuity of the coal has been 

 proved in the case of three of the coal- veins. As there is practically 

 the same sequence of strata on both sides of the fault, it is con- 

 cluded that the ' overthrusts ' did not take place till all the 

 coal-seams of the Eadstock Series had been deposited. The areas of 

 ' dead ground,' sometimes considei'ed to be wash-outs, are probably 

 also the result of movement. The areas occur near faults, frequently 

 take a course parallel to overthrust faults, and at their margins 

 the coals are often reduplicated. ' Dead ground ' is usually found 



