520 THE COLLIERY GUARDIAN. September 10, 1915. Geological Research in the Coal Fields during 1914. In his introduction to the summary of progress of the Geological Survey and Museum for 1914, Dr. Aubrey Strahan, the Director, states that the field work was carried on in England and Wales in the three districts of (1) Denbighshire, with parts of the adjacent counties; (2) Warwickshire and Staffordshire; (3) London and the South-East. In the Denbighshire district work was carried southwards in Shropshire as far as Shrewsbury, and in the lower palaeozoic rocks west of the carboni- ferous tract. The small part of Lancashire, including Liverpool, which falls within the 1 in. Sheet 96, was surveyed. In Warwickshire much attention has been devoted to the red unproductive measures which form the uppermost part of the carboniferous group. In the London and South-Eastern district the work has pro- ceeded eastwards on both sides of the Thames. All three divisions of the chalk and the lower London tertiaries have come under examination, as far upwards in the sequence as the Claygate beds, an outlier of which has been detected near Willesden Green. In all three districts the superficial deposits are of great importance in respect both of wideness of distri- bution and thickness. In Scotland the mapping of the interior of the Island of Mull has been completed, and that of the Highlands has been continued. The revision of the coal measures of the Lanarkshire coal field has been completed during the past year by the mapping of the Hamilton district. Denbighshire and Shropshire District. During the past season the examination of the Liver- pool district, necessary to complete the re-survey of the New Series Sheet 96, has been commenced and nearly completed. In the Wrexham Sheet (121) further infor- mation has been collected. In the Oswestry Sheet (137) the survey of the Denbighshire coal field has been carried southward as far as Oswestry; the mapping of the older rocks on the west has advanced beyond the Tanat Valley towards Llanfyllin, and the newer formations on the east have been investigated as far south as the River Vyrnwy. Work has been commenced in the Shrewsbury Sheet (152) also, between the county town and Wellington. Mr. Wedd finds that the lower and middle coal measures are everywhere covered with drift within the area surveyed near Oswestry. No collieries are at present working within the district, and the only explora- tion recently carried out consists of three borings at Day wall Colliery, Gobowen, the cores of which are being examined. Red upper coal measures, which should apparently be assigned to the Ruabon marls, have been worked for brick-making at the Sweeney Brick Works, south of Oswestry. They are of the usual type of purple clay, with one or two thin beds of grey, apparently ashy, sandstone resembling the Espley rock. An exposure of permian sandstone, indicated on the old map near Oroes-Wylan, on the south side of Oswestry, is now concealed, and the rock has been seen nowhere else. It may be presumed to belong to the Erbistock or Keele beds. Between Shrewsbury and Haughmond Hill the red Keele beds overlying the productive coal measures of the Shrewsbury coal field, and represented on the old map (61 N.W.) as permian, have been found by Mr. Cantrill to be almost concealed by glacial drift. The only good section so far discovered is that afforded by the banks of the Severn at Monkmoor, where purple-red flaggy sandstone, and purple, red, and lilac-coloured marls are exposed. Between Haughmond Hill and Roden a small area of brown sandstone free of drift has been detected at 'Somerwood, while white and crimson clay has been dug, and lavender-coloured sandstone quarried, in the valley of the Roden, north and east of Roden village. A boring for water at Roden proved at the most only 17 ft. of Keele beds, under the drift and overlying the Longmyndian rocks. South of Oswestry, Mr. Webb finds that the trias extends farther west than is shown on the old map. The bunter outcrop, with a general south-south-westerly strike, not only oversteps the Erbistock or Keele beds (the permian of the old map), but transgresses on to at least the sandy limestone group of the carboniferous limestone. Thus, whatever the relationship of the Erbistock beds to the underlying coal measures, a strong unconformability marks the on-coming of the trias, here as in North Denbighshire and elsewhere. Moreover, the south-south-westerly strike of the trias is maintained across at least one important northward downthrow, so as to suggest that such faulting is of pre-triassic date. The local rapidity of the transgression is susceptible of ready explanation. For many miles northward all the strata have a general eastward dip, and the bunter comes on regularly above the Erbistock beds w’ith no obvious discordance. But from Sweeney Mountain southward the carboniferous rocks seem to have been uplifted anticlinally and faulted, sufficiently to have led to the cover of coal measures being removed, and the lower carboniferous rocks partially denuded in pre- triassic time. Warwickshire and Staffordshire District. Warwickshire Coal Field.—The following grouping of the productive measures and of the closely associated overlying red and grey unproductive strata, already recognised in the northern and central parts of the coal field, is applicable also to the southern end :— South of Hawkesbury, Mr. Eastwood finds that the coal measures below the Keele group are concealed either under drift or trias. Numerous old pits have reached the coals belowr, and the records when available have been examined. The present workings of Binley Colliery prove the extension of the workable seams south-east of Coventry. At Hawkesbury and Exhall collieries, and also in the borings at Keresley and Whitmore, the thick coal is practically one seam; but, south of Hawkesbury, it begins to split, and at Wyken (Alexandra) Colliery, la- rnites to the south, it is represented by the Slate and Ell coals, separated by 11 ft. of fireclay. Farther south, the distance apart of these seams increases. The Seven- feet coal, 90 ft. below the thick coal, also appears to split up southward into several thin unprofitable seams. At the old Wyken Colliery, one mile south-south-east of Hawkesbury, the record gives 60 ft. of red measures lying 187 ft. above the Two-yard coal, and the same thickness of similar strata is mentioned as occurring at 174 ft. above the Two-yard coal at the Alexandra pits, half-a-mile to the south. The overlying keuper sand- stone is nearly horizontal in both cases, but the red measures and the coals below dip west at 1 in 4 (14degs.). To refer these red measures to the permian, as was suggested many years ago,* implies the local denudation of over 600 ft. of measures, since within short .distances to the north-east and south-east the base of the Keele group has been proved to be never less than 800 ft. above the Two-yard coal. It is more likely, then, that the red strata are either the upper part of the lower grey measures stained ?ed by percolation through the overlying trias; or that, as is more probable, they represent the lower beds of the Etruria marls, on the strike of which the shafts are situated. The survey of the upper red sandstones and marls has been carried to the southern margin of the map (169). The lower, or Keele, group is poorly exposed. In the middle group the Exhall conglomerate has been traced by Mr. Eastwood for about a mile south of Exhall, chiefly by the presence in the soil of abundant pebbles of yellow chert and some of a grey limestone (probably of carboniferous age). The Corley conglomerate, mainly a dull red sandstone, with lenticles of con- glomerate containing Silurian pebbles, some cherts, but rarely any of limestone, forms a well-marked feature between Corley and Keresley. South of Keresley the outcrop is ill-defined, though it is still traceable through Coventry to Whitley Common. A good section, with the conglomerate exceedingly well developed, is seen at Radford, where the main road to Fillongley crosses the railway. It is also recorded in the borings for the Coventry Waterworks at Spon End and Whitley. The highest beds of the upper red series occur around Tile Hill in the area surveyed by Mr. Cunnington, who estimates that they are 2,500 ft. above the base of the Keele group. They consist of bright red marls passing imperceptibly into marly sandstones. Thin conglomerate bands, containing pebbles of yellow chert and an occa- sional specimen of crinoidal limestone, are present; the best examples are exposed in an old quarry at Beech- wood. Whitmore Park and Keresley Borings. — In the southern part of the coalfield sections of the productive measures of the Etruria marls, and of the Halesowen group, are seldom obtainable; while owing to changes in dip, coupled with false bedding, calculations as to the thickness of the upper red sandstones and marls, obtained from outcrop measurements, are not reliable; but the information is supplied by two borings put down by the Warwickshire Coal Company—one near Newland House Farm, Keresley, and a second near the Rifle Range, Whitmore Park, 2| miles south-east of Keresley. Permission to examine the material, and also that of the shaft sinking still in progress at Keresley, has been kindly granted by Mr. W. P. Evans, of Coventry. Both borings commenced below the Corley con- glomerate, and were continued down to the thick coal, which was entered at a depth of 2,096 ft. at Keresley, and 2,421 ft. at Whitmore. They therefore afford direct measurements of the thickness of the Etruria marls, Halesowen group, Keele group, and of more than half of the middle group. The thick or main coal, as the following sections show, contains only •thin partings. Whitmore. Ft. in. Coal 4 1 Parting 0 3 Coal 2 3i Parting 0 I Coal 4 u Parting 0 1 Coal 1 10 Fireclay 1 0i Coal 2 4i Parting 0 1 Coal 5 | Keresley. I Ft. in ! Coal ............... 2 1 I Fireclay ........... 0 4 I Coal .............. 11 6 Parting ........... 0 1 Coal ................ 5 2 Parting........... 0 1 Coal .............. 0 11 Unproductive series, 3,250 ft.— Thickness Uprer red sandstones and marls— in feet. Upper group .............................. 750 - Middle group ........................... 1,000 Lower (or Keele) group................. 1,900 Upper grey measures (Halesowen group) ..... 450 Lower red marls (Etruria marl group) ...... 150 Productive series, 500 ft.— Lower grey measures........................ 500 The Keresley boring was carried down 57 ft., and the Whitmore boring 123 ft., below the Main seam. A bluish-black shale, 5 ft. thick, and 139 ft. above the top of the Main coal at Whitmore, was matched very closely by a band, 4 ft. thick, at a height of 151ft. above the Main coal at Keresley. The presence in each boring of this bed of a peculiar character, and the fucoid-like markings, suggest that it is one of the marine bands, but no shells were found in it. It is difficult to recognise the beds below the Halesowen group as the equivalents of the red Etruria marls as developed at their outcrop. Except for an occasional bed of mottled shale, the whole group in each * “ The Geology of the Warwickshire Coal Field,” Memoirs, Geological Survey, 1859, pp. 21, 30, 31. boring is grey and far more sandy than usual. However, the beds described as coarse sandstones in the records are of the same type as the Espley rocks seen in the red marls in the northern pit of the Haunchwood Brick Company. It should also be remembered that in most of the records of shaft-sections south of Nuneaton, beds in the position of the Etruria marls are described as red and grey binds with mingled ground and coarse sand- stones. The Halesowen group compares closely with the development at outcrop, but, in the Whitmore boring, contains more sandstone than usual, and the index lime- stone is slightly higher. The index limestone is much lighter in colour than the bands in the Keele group, and Spirorbis is far more abundant. This is characteristic of the limestone over the coal field, and, as its name implies, it forms a reliable index of the depth to the Thick coal or its equivalents. The varying character of the Keele group will be gathered from the illus- trations. It will be seen that the group is thicker in the north (Keresley) than in the south (Whitmore), thus agreeing with the general thinning out of the rest of the carboniferous rocks in this direction. In mapping the WHITMORE PARK. DEPTH FROM SURFACE Soft red Sandstone 668 1637 3 HEIGHT above ORDNANCE DATUM KERESLEY DEPTH. FROM SURFACE Red marls br Sandstones i Fxhaii Conglomerate 1538 Red Sandstone Spirorbis Limestone- Red mar! with thin Sandstones 2083 2209 2282 Grey Sandstone with red mar! Red mar! Blue mar! Index Limestone^ Blue 4 brown mar! Coal 0Ft.3!ns. Grey Sandstone Coal OFt. 3 Ins. Grey Sandstone Grey Sandstone Mottled Shales Grey Shales, Fireclay &■ Espley Rocks 2443 Thick Coal 21 Ft '. Bins. Marine Horizon ? 1306 1331 14'13 412 49Q Spirorbis Limestone Sandstone with thin beds of Marl Red marl with thin beds of Sandstone Maris with thin Sandstones HEIGHT ABOVE ORDNANCE DATUM Grey Sandstone - Spirorbis Limestone Index Limestone Grey Sandstone Coal OFt. Sins. 1783 1864 1945 2116 Marine Horizon ? Thick Coat 20Ft. 2ins. Grey Sandstone Grey Shales, Fireclay 4 Espley Rocks SCALE O 200 400 600 FEET Sections of Deep Borings to the Thick Coal in the Warwickshire Coal Field. district, the base of the Keele group was taken at the first bed of red marl above the essentially grey beds of the Halesowen group. But in both of the borings grey sandstones occur above the first band of red marl. The rest of the sequence up to the Exhall conglomerate or its horizon consists of bright red marls and dull red sandstones. Although the sandstones are frequently marly, and include beds of marl, while the marls con- tain thin sandstones, they can be grouped into rela- tively thick alternating beds of marl and sandstone. The nodular bed of Spirorbis limestone at 490ft. depth at Keresley is probably represented by a bed found by Mr. Eastwood near Astlcy Court and by limestone made up of brecciated fragments near Great Lynes Wood. At the base of the middle group the Exhall con- glomerate in the Whitmore boring is identical in com- position with that seen at Exhall, and in the Keresley shaft at a depth of 440 ft., but it does not occur in the Keresley boring. In the beds above the con- glomerate the borings show a great divergence in composition between the two localities. South Staffordshire Coal Field.—A small area only has been surveyed in the Halesowen district, as shortly after entering upon it Mr. Cunnington left for military service. It appears that the well-known Clent breccia at the base of the bunter is stratigraphically separable from the underlying “ so-called ” permian, and is in many respects comparable to the Hop was breccia of the Tamworth district. In this connection it is of import- ance to note the occurrence in some borings at Saltley, of similar breccias below the bunter conglomerate, which thus form a connecting link between those of Clent, Sutton Coldfield and Hopwas. Keuper.—The mapping of the lower keuper sandstone, flanking the East Warwickshire coal field, has been com- pleted by Mr. Eastwood. Its precise limits under the thick drift cannot be determined, but there is no doubt that it gradually transgresses the older formations from north to south. Thus, at Marston Jabbett, it rests on Stockingford shales, near Hawkesbury on the lower grey group of the coal measures, and in the extreme south on the Corley conglomerate. Whether, in places, the juxtaposition is due to faulting, as shown on the old one-inch map, is uncertain; but the cutting of the new loop line between Parting of the Heaths and Pinley shows that the keuper here overlaps and is not faulted against the Keele beds.