THE BARAKAR-IRONSTONE BOUNDARY NEAR BEGUNIA, RANIGANJ COAL-FIELD. BY CYRIL S. Fox, D.SC., M.I.MIN. E., F.G.S., Officiating Superintendent, Geolo gical Survey of India. (With Plates 28 and 29.)

THE

'HE re-survey of the Raniganj coal-field now in progress has shown that the junction between the Barakars and the overlying Ironstone Shales is normally a conformable one. It is at a higher geological horizon than is suggested by its position, north of the Grand Trunk road at Begunia, on Blanford's map. This junction really follows a line in a W.S.W. direction from north of Kulti and south of Begunia to the Barakar river. It is a faulted boundary. The shales shown in the sketch of the Jain temple section by W. T. Blanford 1 are carbonaceous, but they do not contain ironstone, and for this reason should be included in the Barakars. Furthermore these shales are overlain by the pebbly sandstone, of a Barakar facies, which forms the ridge on which Begunia is situated. It has, however, been difficult to explain the apparent remarkable unconformity to which Blanford drew attention.

While working on about the same geological horizon, i.e., above the Chanch seam, which is the westward continuation of the Begunia seam, in the Khudia nala near Chanch, I discovered an exposure showing the finest example of false- or current-bedded sandstone that I have seen. The real dips of this sandstone are to the southeast while the planes of current bedding dip northward. (Plate 29). It immediately occurred to me that, as this sandstone was almost certainly the same as that on which the Jain temples at Begunia stand, the northerly dips, which are so evident in the sandstones between Begunia and Barakar, might really be the dip of planes due to current bedding. (Plate 23, fig. 2.) On careful examination, particularly of a small quarry, which was not open in Blanford's day, just north of the Grand Trunk road and east of the road to Barakar station, I found that the planes of apparent bedding do not continue to the surface of the sandstone. This they should do if the surface of the sandstone was a weathered and eroded unconformity. The low southerly dip is the true dip of

2 Mem. Geol. Surv. Ind., III Art. 1, (1865), p. 42.

these sandstones. It agrees with the dip slope of the sandstones at the Jain temple exposure, as well as with the southerly dip seen in the Chanch (Khudia) section. The northerly dips in the quarry are undoubtedly those of the planes of false-bedding. This will be seen from a scrutiny of Plate 28, fig. 2. In short there is no 'roll' of the beds, and certainly no unconformity. The exposures in that area convey a wrong impression to the mind if the meaning of the details in the quarry section is not grasped. Without the quarry section, which was not open in Blanford's time, it would be quite impossible to arrive at any other conclusion than that of Blanford. A true explanation of the observed facts is shown in the accompanying sketch section.

PLATE 28. FIG. 2.-Barakar sandstones in a quarry, Begunia, near Barakar railway

station.

PLATE 29.-False-bedded Barakar sandstone at Chanch, Raniganj coalfield.

THE RANIGANJ-PANCHET BOUNDARY NEAR ASANSOL, RANIGANJ COAL-FIELD. BY CYRIL S. Fox, D.Sc., M.I.MIN.E., F.G.S., Officiating Superintendent, Geological Survey of India. (With Plates 28 and 30.)

IN

N his survey of the Raniganj coalfield W. T. Blanford (Mem. Geol. Surv. Ind., III, pp. 126-131) gives a short clear description of the Panchets and states (p. 127) that there is a slight unconformity between the Panchet and the underlying Raniganj stage. He does not, however, mention the fossil-wood horizon in which the fossil tree was found near Asansol. The re-survey of the Raniganj coalfield has now proceeded far enough for a definite opinion to be given with regard to the exact boundary between the Raniganj stage and the overlying Panchet beds.

Mr. Sethu Rama Rau, Assistant Superintendent, Geological Survey of India, working south of the Damuda river, has found a wellmarked fossil-wood sandstone almost at the top of the Raniganj stage. Mr. A. K. Banerji, Assistant Superintendent, Geological Survey of India, working from the Damuda river north-eastwards by Patmohna and Hirapur to the Kumarpur railway cutting on the East Indian Railway two miles west of Asansol, has traced the same fossil-wood horizon to this place, and finds that this horizon must be included in the Raniganj stage and not in the Panchet stage. I have seen the chief sections on which Mr. Banerji bases his opinions and agree with him that there is a slight but local unconformity (Plate 28, fig. 1) between the undoubted Panchet beds and the underlying strata in which the fossil-wood sandstone occurs. This fossil-wood sandstone is of considerable value as a stratigraphical horizon, as it can be followed across the whole of the western part of the Raniganj coalfield.

The fossil tree erected in the Indian Museum comes from the fossilwood sandstone exposed in the Kumarpur railway cutting west of Asansol. This tree, according to Professor B. Sahni, belongs to 'the Cordaitales, one of the most important groups of Palaeozoic Gymnosperms.' Details of the discovery are given in the Records, Geological Survey of India, LVIII, pt. 1, 1925, pp. 75-79. In this account it was stated that the sandstone in which the silicified tree trunks were found belongs to the Panchet beds. The reasons

for this opinion are not stated. I found another silicified tree trunk in the same cutting in October 1925 (Plate 30, fig. 2). This was extracted and brought to Calcutta, but has not yet been mounted. It was nearly 50 feet long as it lay when fully exposed. Professor Sahni, considered that the first tree belonged to the genus Dadoxylon and showed well-marked growth rings (Plate 30, fg. 1). He gave no name for the species. He, however, drew attention to the fact that it was very similar to two species--namely D. indicum, Holden, from Deogarh, and D. bengalense, Holden-from Brahmanbarari in the Jharia coalfield. Both these species were from the Barakar stage of the Damuda series (Lower Gondwanas). Seeing that the palaeontological evidence supports a Palaeozoic rather than a Mesozoic age I feel that an uppermost Raniganj age rather than a lowest Panchet age must be accepted for the fossil-wood sandstone and suggest that its official designation might be the Kumarpur (fossilwood) sandstone.

This is the only fossil-wood (silicified) horizon known in the Lower Gondwanas, and should it be also found to occur in the eastern part of the Raniganj coal-field, will be of great use a stratigraphical horizon.

as

LIST OF PLATES.

PLATE 28, FIG 1.-Panchet-Raniganj unconformity in stream near Junut village, Raniganj coalfield.

PLATE 30.--FIG. 1.-Fossil tree from Kumarpur railway cutting showing rings of

growth.

FIG. 2.-Fossil tree in Kumarpur railway cutting.

A PERMO-CARBONIFEROUS MARINE FAUNA FROM THE UMARIA COAL-FIELD. BY F. R. COWPER REED, M.A., SC. D., F.G.S. (With Plates 31 to 36.)

INTRODUCTORY REMARKS.

THE fossils described in this paper were collected from beds associated

with those of undoubted Lower Gondwana age at Narsarha railway cutting, Umaria, Rewah State, Central India, in 1922, but the presence of marine fossils at this locality had been observed in the previous year. A brief note on their occurrence was published in the General Report of the Geological Survey for 1921 1, but no precise determination of the specimens was given. In this report it was observed that the most abundant fossil was a species of Productus which Mr. Tipper considered to be new to India; and this shell forms practically the whole of the shell-band, 3 inches thick, which contains most of the fossils. Another brachiopod attributed to Spiriferina was also mentioned, and it was regarded as "close to and probably identical with Sp. cristata var. octoplicata.” The shell-band is described as resting on quartz-grits which pass up conformably through it into sandstones of Lower Barakar age.

The description of these fossils, which were sent to me for identification in 1925, had been finished and the plates to illustrate them had been drawn when further material collected by Mr. E. R. Gee in 1926, was submitted to me, necessitating a revision of my previous work and throwing further light on the stratigraphical age of the beds. These new fossils were found in the same locality on both sides of the Narsarha railway cutting two miles west of Umaria railway station in four distinct bands, the lowest one D, (K 23-264) containing large numbers of small gasteropods in a gritty clay; the next one, C, (K 23-263) lying 2 feet higher and containing chiefly brachiopods, in red and olive-green clays associated with the Productus shell-band and about 8-9 inches below the succeeding horizon, B, (K 23.262) which is a yellow brown sandy clay 1 inches thick. The highest horizon, A, (K 23-261) is an 8-inch band in the soft fine yellow sandstone of the basal Barakar series, and contains many specimens of Productus, Pleurotomaria, etc.

1 Fermor, Rec. Geol. Surv. Ind., Vol. LIV, pt. 1, August 1922, pp. 14-16; Nature, Vol. CX, 1922, p. 556; Wadia, Geology of India', 2nd edit., 1926, London, p. 148.