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altered dolerite (epidiorite) dykes, and covered in part by four flows of Deccan Trap. The granite-gneiss shows the same uniformity of composition over large areas, the biotite being rarely replaced partly or entirely by hornblende. It is in all probability an orthogneiss. Rare occurrences of epidote-granite gneiss are met with, and the granite-gneisses marginal to the epidiorite dykes are characterised by hornblende. Basic patches, schlieren, or cognate xenoliths occur, composed of either sphene, black iron-ore, apatite and epidote along with crowded flakes of chloritized biotite, or of a dense aggregate of flakes of bluish-green uralitic hornblende associated with many grains of epidote and sphene; both types are set within a ground-mass of ordinary biotite-granite-gneiss. Intruded into these ortho-gneisses are rare pegmatite veins composed of hieroglyphic intergrowths of glassy quartz with pink orthoclase or microcline. Quartz reefs, which are well jointed and nonauriferous, traverse the granite-gneisses; these are sometimes faulted, and are invariably older than the epidiorite dykes, for in every case the latter are seen to cut across them. Of the thirty-five quartz reefs which occur in the area and which vary in width from 15 to 100 paces, the majority strike N. E.-S. W. The epidiorite dykes vary in width from 10-110 paces, and are far more numerous than the quartz reefs, for there are one hundred and fifty-nine. All the basic dykes, except a few of amphibolite, are composed of altered dolerite (epidiorite), which is occasionally coarsely porphyritic. They frequently branch, and intersect each other, and their course is often curved. The majority of them strike more or less due east and west. Some of the dykes contain micro-pegmatite in which there is seen a tendency to radial structure similar to that in a granophyre. Very often the Very structure of their mass is highly granulitic. Between the granite. gneiss and the Deccan Trap series are the boundary "Red and White Beds." Fossiliferous Lameta beds were met with at two localities only. Two furlongs south-south-west of of Nawaapet, (17° 43′ 30′′ 78° 23′ 45′′), is a thin lenticular bed of pale calcareous Lameta shale resting directly upon calcified hornblende granitegneiss covered by Deccan Trap basalts. This bed contains in large numbers a fossil fresh-water Unio belonging to an undescribed species of the new genus Indonaia.

One mile north-north-west of Anantawaram, between the first basalt flow and the underlying biotite-granite-gneiss, a brown chert

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containing indeterminable fossil fragments, probably of Unionidæ, occurs. A part of the gneissic area is covered by four separate horizontal flows of Deccan Trap, but the small outliers of the latter indicate a former wider extension, which probably included the site of the city of Hyderabad. West and south-west of Hyderabad, the ragged edges of the four basalt flows which have been cut back may be observed. None of the four basalt flows are olivinebearing; their thicknesses from below upwards are respectively 34 feet, 111 feet, 96 feet and 74 feet. Between these basalt flows are inter-Trappean beds of green earth, limestone, chert and geode-bearing vesicular basalt.

The first part of the field season was spent by Mr. D. N. Wadia in a continuation of his mapping of the Punjab and Poonch. Rawalpindi district. In the country between Mozaffarabad and Jhelum the entire zone of hills has been subject to a geniculate bend of nearly 110°, the axis of the “knee” being the Jhelum River.

During the latter half of the season the survey of the Poonch Ilaqa was completed. In last year's report it was stated that the suggestion that the Kiol or Kuling beds of Lydekker included Nummulitic strata was confirmed by the discovery of nummulites by Mr. Wadia. These specimens have since been subjected to more careful examination, and although the imperfect fragments decidedly resemble nummulites, they are, according to Mr. Tipper, more probably members of the Fusulinido. The Nummulitic age of part of these beds must therefore be regarded as not yet definitely proven. In the Mendhar and Bagh tahsils it has been found possible. to split the Murree series into two stages, an upper and a lower, based on lithological differences and on the frequent presence of plant remains and woody tissue in the upper.

During the field-season the Rajputana party resumed the geological survey of Rajputana which had been Rajputana. interrupted in 1916 by economic enquiries connected with the War, and had not been since resumed except for a visit to the Jodhpur part of the area by Messrs. Tipper and Crookshank in the field-season of 1920-21 (vide General Report for 1921). The party consisted of Dr. A. M. Heron, officiating Superintendent in charge, with Sub-assistants B. C. Gupta and L. A. N. Iyer, under training. The survey was taken up in the neighbourhood of Beawar, where it had been discontinued in 1916,

and during the season three standard sheets, on the 1-inch-to-1-mile scale, Nos. 165, 166 and 167 of the Central India and Rajputana Survey, were completed except for a portion of the Udaipur (Mewar) State in the south-east. The adjoining portions of sheets 140 and 168 were also touched on. Politically the area surveyed consists of the major portion of the Merwara sub-division of the British district of Ajmer-Merwara, and of a part of the Jaitaran pargana of Jodhpur (Marwar) State, adjoining Merwara along its northwestern border.

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Topographically the area is characterised by its division into five zones, which extend in an approximately N. E.-S. W. direction, the general strike of the rocks; this physiographical division reflects with great faithfulness the geological structure. Rocks belonging to two systems are present in alternate zones, two of these being occupied by varied metamorphics of the younger system correlated with the Delhi system of Jaipur and Alwar and three by gneisses of the older group, which we may consider as probably belonging to the Aravalli system. So far we do not know the relationship of the Aravallis of north-eastern Rajputana and Jaipur to the gneisses and biotite-schists of the great plain of Kishengarh and south-eastern Ajmer, but the two groups are similar, except that in the latter the proportion of granites and banded granitegneisses is higher. This increase in the amount of igneous intrusion is quite in accordance with the other observations, from which we infer that as we go westwards, transverse to the axes of folding which determine the "grain" of the country, from Alwar through Jaipur to Ajmer, we are passing from the flanking folds of the ancient Aravalli chain to its central core where metamorphism and igneous permeation reach their maxima. We may perhaps consider the Aravalli system to be part of the Archæan, at any rate the older rocks of this system are of typically Archæan

facies.

Only the central and the north-western belts of the older rocks were examined this year, with a narrow strip of the south-eastern belt where it underlies the newer system. Dr. Heron reports that in the north-western belt the most prominent rocks are a group of limestones in massive beds, overfolded in several isoclines, the axial planes of which dip to the north-west at high angles. They form high, straight and almost continuous ridges extending for about 50 miles, and the celebrated marble of Makrana in Jodhpur

appears to occur along their strike continuation to the north-east. For the most part they are coarse, white, saccharoidal marbles, with diopside and white mica; interbedded with them are bands of finer and less crystalline, blue-grey, "sandy sandy" limestone, the sandy" appearance being due to knots of secondary felspar, quartz and calc-silicates weathering in high relief. Dark calcgneisses occur sparsely. Lapping round the ridges and exposed in valleys between them, in such a manner as to suggest that the limestones are folded into it, is a grey, foliated, porphyritic gneiss of a fairly uniform granitic composition, which comprises the remainder of the north-western belt of older rocks. This is probably a granite magma which has invaded the limestone series, removing or absorbing the non-calcareous portion of the assemblage, or it may be the result of the complete metamorphism and recrystallisation of the non-calcareous members of the series. The contact between limestone and gneiss is sharp, and there is no passage of one into the other. The gneiss is much intruded by later pegmatites, which are absent from the limestones.

The central belt is composed of porphyritic banded gneisses which are in part the dark Aravalli porphyritic biotitic granite, often bearing garnet and magnetite, and in part biotite schists injected with this granite and later acidic granite and pegmatite, the various types being interbanded and rolled out together in the greatest complexity. To the south-west this band narrows and is finally eliminated by the convergence of the two flanking synclines of the younger series, while to the north of Beawar it disappears beneath alluvium. Along it runs a line of small plugs of a comparatively little-altered dolerite, which is probably the latest intrusive here present.

Only the north-western edge of the south-eastern Aravalli area was examined. The dead-level plain which stretches through southeastern Ajmer and the Kishengarh and Jaipur States is almost unbroken except for a few hills composed of outliers of the Delhi system. Along the edge runs a narrow band of the dark porphyritic gneiss, varying in all degrees from a coarse biotitic granite through banded varieties to a fine mylonite with the felspars entirely destroyed. Beyond this is a wide extent of biotite schists and granulites, intruded by large and small bodies of the Aravalli granitic gneisses and saturated with pegmatite from that granite, forming the "migmatite" of Sederholm. These schists are the oldest rocks

met with, and in them the gneiss (really a foliated granite) is intrusive, with its pegmatite, other younger fine-grained acid granites, epidiorites (amphibolites), pegmatite from the post-Delhi granite magma, and still later doleritic rocks.

Shearing and mylonisation occur principally along the contact with the younger series and have been caused by the sliding of the younger syncline over the older complex, with an imposing development of shear-breccias, "flinty crush-rocks" and "trap-schotten gneiss."

Alternating with the three belts of older rocks, the younger system is exposed in two symmetrical isoclines, dipping in general towards the north-west. In the type area of the Delhi system, Alwar and Jaipur, it is broadly divisible into the Alwar series, a great thickness of quartzites, succeeded upwards by the Ajabgarh series, and by as great or even greater a thickness of argillaceous and somewhat calcareous rocks. Round Ajmer quartzites are in force, but in this season's area they have disappeared except for puny representatives; it is not yet clear whether their absence is due to their having died out to the southward, with the upper argillaceous and calcareous series overlapping them on to the Aravalli system.

Only a very general agreement can be made out between the succession in the two synclines, and each is in itself quite asymmetrical. This is no doubt due to intensely compressed folding with "sliding" and overthrusting, resulting in the partial elimination of one limb of the syncline, as is the case in the Alps and the Highlands of Scotland. Unfortunately in the Aravalli range the folds never approach horizontality, their axial planes generally dipping north-westward at angles from 50° to vertical; this and the moderate height of the ridges render available only very short sections for study along the direction of dip; consequently thrust-planes are almost impossible to trace in such highly folded rocks. It is still hoped, however, that further strike-mapping may clear away some. of the complexities.

Dr. Heron reports that, commencing with the south-eastern margin of the south-eastern syncline, the basement bed, resting on the older complex, is a thin arkose quartzite. This is continuous along the strike with the great unconformity conglomerate which between Srinagar and Kishengarh has a breadth of outcrop of over a mile; this, allowing for the folding seen in it, gives a thickness

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