Aravalli Hills Research Articles

Fallibility of Palaeo-Channels as Groundwater Potential Zones in a Part of Thar Desert

Abstract Integrated analysis of field data indicates that the Thar desert had a longer network of drainage in the past. Saraswati had been one of the major rivers. Aerial photointerpretation has been useful in definite identification of Kantli palaeo-channels in areas adjacent to the Aravalli hills. Signatures of palaeo-channels on space imagery are sometimes misleading as similar reflections are recorded from dunal depressions also and, hence. must not be thought of as indicating groundwater potential zones.

Polymodal Volcanism in Parts of the South Delhi Fold Belt, Rajasthan

Abstract The Proterozoic South Delhi Fold Belt (SDFB) is known to have a dominant volcanic component along the western flank of the Aravalli Range. Earlier studies have indicated both bimodal and unimodal characters of these volcanics in different parts of the SDFB. The Shyopura-Narpura area in north-central part of the Aravalli Range has, on the other hand, volcanics of intermediate and ultrabasic composition, interlayered with basic and felsic volcanics. This polymodal suite of secondary greenstone character is interpreted to have erupted in a rifted back-arc setting.

SPOT image data as an aid to structural mapping in the southern Aravalli Hills of Rajasthan, India

AbstractThe 10 to 20 m resolution of SPOT image data, together with their potential for stereoscopic viewing, provides an excellent base for geological mapping inremote and rugged terrain that is akin to high-level aerial photographs. Their large format (60 × 60 km) also gives the advantage of synoptic coverage that ranks with images from the Landsat series of satellites. Use of stereo pairs of single-band SPOT images has enabled some revision of existing geological maps of the southern Aravalli Hills in Rajasthan at a scale of 1:100000, and has added significantly to knowledge of their complex mid-Proterozoic structure. In particular, many possibly early low-angled faults have been discovered, together with the tectonic nature of a major terrain boundary and much detail of intricate structures has been added in the more remote areas. The potentialfor lithological discrimination of multispectral SPOT data is severely limited by its restricted coverage of geologically important spectral features, and it is far surpassed by that of Landsat Thematic Mapper data, which would have been capable of more comprehensive lithofacies reconnaissance, had they been available.

Regional tectonic framework, structure and evolution of the western marginal basins of India

The Kutch-Saurashtra, Cambay and Narmada basins are pericontinental rift basins in the western margin of the Indian craton. These basins were formed by rifting along Precambrian tectonic trends. Interplay of three major Precambrian tectonic trends of western India, Dharwar (NNW-SSE), Aravalli-Delhi (NE-SW) and Satpura (ENE-WSW), controlled the tectonic style of the basins. The geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults. The Kutch basin opened up first in the Early Jurassic (rifting was initiated in Late Triassic) along the Delhi trend followed by the Cambay basin in the Early Cretaceous along the Dharwar trend and the Narmada basin in Late Cretaceous time along the Satpura trend. The evolution of the basins took place in four stages. These stages are synchronous with the important events in the evolution of the Indian sub-continent—its breakup from Gondwanaland in the Late Triassic-Early Jurassic, its northward drifting during the Jurassic-Cretaceous and collision with the Asian continent in the Early Tertiary. The most important tectonic events occurred in Late Cretaceous time. The present style of the continental margins of India evolved during Early Tertiary time. The Saurashtra arch, the extension of the Aravalli Range across the western continental shelf, subsided along the eastern margin fault of the Cambay basin during the Early Cretaceous. It formed an extensive depositional platform continuous with the Kutch shelf, for the accumulation of thick deltaic sediments. A part of the Saurashtra arch was uplifted as a horst during the main tectonic phase in the Late Cretaceous. The present high thermal regime of the Cambay-Bombay High region is suggestive of a renewed rifting phase.

Present status of the geochronology of the Precambrian rocks of Rajasthan

Age determinations, mostly by RbSr analyses, of the Precambrian rocks of Rajasthan by us and by others are summarized and discussed. Broad periods of acid magmatism at (1) 3000−2900 m.y., (2) 2600−2500 m.y., (3) 2000−1900 m.y., (4) 1700−1500 m.y. and (5) 850−750 m.y. were identified. The oldest rocks in the area are the yet undated banded gneisses (BGC) east of Udaipur, intruded by the Untala granite dated at 2950 m.y. and hence of mid-Archean age. The basal status hitherto attributed to the Berach granite dated at 2600 m.y. is no longer tenable. The radiometric control on the beginning and duration of the overlying Aravalli Supergroup is not yet satisfactory, though a lower limit at 2000 m.y. is indicated. Heron's original Delhi rocks have recorded two magmatic events widely separate in space and time. While the earliest granitic activity at 1600 m.y. is recorded only in the Alwar basin in the northeast, the younger activity between 850-750 m.y. is widespread, as shown by the nearly concordant ages of “Erinpura-type” granites along the Aravalli mountain Range and the Malani rhyolites in the western plains of the Aravalli Range.

Post-Neogene tectonism along the Aravalli Range, Rajasthan, India

The Aravalli Range runs southwest from Delhi for a distance of about 700 km. Its western margin is well defined, but the eastern margin is diffuse. Five geomorphic provinces are recognized in the study area: the western piedmont plains; the ridge and valley province which in the Central Aravallis occurs at two different heights separated by a fault scarp; the plateau province demarcated from the former by a fault scarp, confined to the Southern Aravallis, and occurring for a short stretch at two heights across another fault scarp; the BGC rolling plains east of the Range; and the BGC uplands south of the above. The scarps coincide with Precambrian faults. A series of rapids and water-falls, together with deeply entrenched river courses across the scarps and the youthful aspects of the escarpments with no projecting spurs, or straight river courses along their feet, all point unmistakably to a recent or post-Neogene vertical uplift along pre-existing faults. Presence of knickpoints at a constant distance from the Range in all west-flowing rivers, the ubiquitous terraces, and river courses entrenched within their own flood-plain deposits of thick gritty to conglomeratic sand, are indicative of a constant disturbance with a gradual rise of the Range east of the knickpoint, wherefrom the coarse materials were carried by the fast west-flowing streams. There is a differential uplift across the plateau scarp together with a right-lateral offset. This epeirogenic tectonism is ascribed to the collision of the Eurasian and the subducting Indian plates and to a locking of their continental crusts. By early Pleistocene, with the MBT gradually dying off, continued plate movement caused a flexural bending of the plate by a moment generated at the back, and a possible delinking of the continental crust along the zone of subduction. The felexural bending ripped open the Precambrian regional faults. The differential uplift and the difference in the distances of the nodes on two sides of the major reactivated fault were possibly caused by a difference in the values of the flexural rigidity and the foundation modulus owing to a slight compositional difference of the constiuent rocks in the two sectors.

Basin Configuration and Sedimentary Stratigraphy of Western Rajasthan

Abstract The region west of the Aravalli Range in Rajasthan witnessed Palaeozoic, Mesozoic and Palaeogene sedimentation, with the Delhi Supergroup and the Malani igneous suite of rocks forming the basement. Cambrian sedimentation was confined to the Marwar Basins-Nagaur and Birmania; the Nagaur Basin being extensive, trending north and northwestwards to Salt Range (Upper Indus Basin). The Upper Palaeozoic remnants appear as Bap Boulder Bed (Upper Carboniferous) and Badhaura Sandstone (marine Permain) along the northwestern fringe of the Nagaur Basin; the Permians are fluviatile in the deeper parts of Jaisalmer area. The Lathi Basin (Liassic) had an extensive spread of fluviatile sediments. The Jaisalmer Basin (Callovian-Lutetian) formed part of the Indus geosyncline, Pakistan. The Palana-Ganganagar shelf (Paleocene-Eocene) had two embayments at Palana and Ganganagar, and extended up to Salt Range. The Barmer Basin (Cretaceous-Eocene) was sloping northwards and tectonically controlled by Cambay graben, Gujarat. Facies variations are exhibited by these Basins.

An Interpretation of the Induction Arrows at Indian Stations

Induction arrows (Wiese vectors) for night-time SSCs and Bays are determined and discussed along with geological and other geophysical data at eight Indian magnetic observatories, from Sabhawala in the Himalayan foothills to Trivandrum on the seacoast in the extreme south.A medium-sized induction arrow at Sabhawala pointing northwards indicates that the region of higher subsurface conductivity lies to the south of Sabhawala, possibly along the Aravalli Hills, and not beneath the Kashmir Himalaya, where the conductive upper mantle appears to be depressed. East-south-east pointing arrows at Jaipur and Ujjain are again indicative of a high electrical subsurface conductivity on the west along the Aravalli Hills and the Cambay region, where high heatflow and gravity values have also been reported, and the upper mantle appears to be elevated.At Alibag, a medium-sized induction arrow points eastward, with the conductive seawater lying on the west. Hyderabad is the only station where small induction arrows (small Z variations), characteristic of an inland station, are observed. Negative Z variations for positive H variations along the Alibag-Hyderabad-Kalingapatnam profile, become positive about 100km east of Hyderabad due to ocean effect from the east coast.Unusually large induction arrows (very large positive Z variations) in the extreme south Peninsular tip (largest one at Trivandrum), so close to the dip equator, are indicative of very strong induced current concentrations near and along this coast. These oceanic induced currents causing the anomalous geomagnetic variations in Peninsular India, appear to concentrate along the coastline and the continental shelf, and flow from north to south along the east coast. The currents concentrate further as they pass through the narrow Palk Strait and the Gulf of Manar between India and Sri Lanka on to Kanyakumari and the Trivandrum coast, and turn northwards along the west coast due to the obstruction provided by the volcanic ridge of Lakshadweep, Minicoy and Amindivi islands lying to the west in the Arabian Sea, about 300km off the Trivandrum coast. The current concentration would turn westwards near Calicut (11°N) and pass north of these islands in a diffuse form. Another current concentration is expected to flow along the Alibag west coast from north to south (so as to explain the reversed coast effect at Alibag), and turn westwards near Calicut to merge with the Bay of Bengal current system. There is no need to postulate a couductor and current channelling beneath the sea near the Trivandrum coast without any supporting geological evidence. There could be a channelling of the induced currents at the interface of the conductive upper mantle beneath the ocean and the less conductive upper mantle beneath the Peninsular India (100-200km), in a step-structure around the coast, which will account for the induction anomalies observed in long-period variations like Sq.

Determinants of Agricultural Productivity in Rajasthan, India: The Impact of Inputs, Technology, and Context on Land Productivity

Much attention has been devoted in recent years to the sources of agricultural development in such regions of India as Punjab-Haryana and Tamilnadu. Yet other states also merit notice because of their special natural and social characteristics, unique agrarian patterns, and less publicized achievements. Thus, we believe it would be useful to investigate the sources of variation in agricultural productivity, defined as the average value of crop output per hectare of arable land, in Rajasthan's 26 districts. (A district in India is an important political and administrative unit below the state level and over villages and tahsils. In Rajasthan, a district's population will typically number 1 million or more.) Dissatisfied as we were with the limited range of explanatory variables that could be brought into standard production function analysis, we followed an alternative method here that seems to yield a superior understanding of important relationships. Located in the west, Rajasthan is on the average poor, dry, and sparsely populated.' Bajra, a millet grown on unirrigated land, is planted on the greatest acreage; overall, nine-tenths of the arable land is devoted to food crops. Sugarcane and cotton are the major cash crops. Much of the west is desert, but the eastern areas receive adequate rainfall for agriculture, although the monsoon is highly variable. Most major towns, including Jaipur, the capital, are found in the more densely populated east. The Aravalli range runs south to north through the state, screening the monsoon rains from the dry desert and near-desert areas bordering Pakistan. Ganganagar district, wedged against Punjab and Haryana in the north, enjoys a canal-based agricultural regime that differentiates it from

Seismicity, earthquake mechanisms and tectonics along the Himalayan mountain range and vicinity

The historical as well as recent seismicity data and the focal mechanism solutions for 48 earthquakes determined from the observations of world-wide standardized stations network (WWSSN) records, were used to investigate the tectonics of the Himalayan mountain system and vicinity. Seismicity maps of the region showing large earthquakes (magnitude 7.0 and above, and damaging earthquakes that caused fatalities) from the earliest time through 1976, and instrumentally located earthquakes for the period January 1963–March 1974 are presented. Eleven of these earthquakes are estimated to be of magnitude 8.0 and above. The earthquake epicenters generally follow the trend of the mountains with greatest concentrations of seismic activity occurring along the Hindu Kush and Pamir mountain ranges, and near the Quetta, Kashmir and Assam syntaxes. Throughout Tibet, however, the distribution of epicenters is rather irregular and no clear trends are apparent. Two aseismic lineaments, one west of the Sulaiman Range and the other in the Assam Valley, are identified. Also, seismic activity in the vicinity of the Counter Thrust (Indus-Tsangpo suture zone) is rather small. Based on the identification of these aseismic lineaments and from a consideration of the geometry and kinematics of the continental collision model, a hypothesis for the origin of the Himalayan syntaxes is presented. Focal mechanism solutions confirm northward underthrusting of the Indian Plate along the Main Boundary Thrust and Main Central Thrust system, and eastward underthrusting along the Burmese Arc. Fault-plane solutions indicate left-lateral motion along the Kirthar-Sulaiman Range, right-lateral motion along the Karakoram Fault, left-lateral motion along the eastern extremity of the Himalayan flank of the Assam syntaxis, and right-lateral motion along the northern part of the Naga Hill flank of the syntaxis. These observations are in agreement with the expected sense of lateral (parallel to the collision boundary) mass movement for the continental collision model. Focal mechanism solutions for three earthquakes in east Afghanistan show NW-SE compression. A near-vertical orientation of the axes of tension in the solutions for two earthquakes in the Hindu Kush region is consistent with the sinking of a remnant slab of oceanic lithospere. Normal fault-plane solutions showing NW-SE extension for two events near Gatok, Tibet, and for the recent Kinnaur earthquake are interpreted to indicate a possible subsurface northern continuation of the Aravalli Range of Peninsular India, and its involvement in the tectonic framework of the region. Focal mechanism solutions of three earthquakes near the southern edge of the Shillong Plateau suggest block uplift of the plateau as a horst along the Dauki Fault. The solution for one earthquake near the Yunnan Graben shows NE-SW extension.

Deformational and crystallization history of the Precambrian rocks in north-central Aravalli Mountain, Rajasthan, India

Abstract Large-scale structures, textures and mineral assemblages in the Precambrian rocks of the Banded Gneissic Complex and the overlying Delhi Group in north-central Aravalli Mountain reveal a complex deformational-crystallization history. In the basement Gneissic Complex at least three deformational events, D 0 , D 1 and D 2 , and two separate episodes of metamorphism, M 1 and M 2 , are recognized. The supracrustal Delhi Rocks display only two phases of deformation, D 1 and D 2 , associated with a single protracted period of metamorphism, M 2 . The first phase of deformation (D 1 ) of the Delhi orogeny (1650-900 m.y.) produced large isoclinal folds that are overturned towards the southeast and have gentle plunges in NE and SW directions. The second phase of deformation (D 2 ) gave rise to tight open folds on the limbs and axial-plane surfaces of the D 1 folds. These folds generally plunge towards the N and NNW at 30°–80°. In the Basement Complex one more deformation (D 0 ) of the Pre-Delhi orogeny (> 2000 m.y.) is recorded by the presence of reclined and recumbent folds with W to WNW trending fold axes. The D 0 folds were superimposed by D 1 and D 2 folds during the Delhi orogeny. The three deformational events have been correlated with the crystallization periods of minerals in the rocks and a setting in time is established for this part of the Aravalli range.

Late quaternary history of vegetation and climate of the Rajasthan desert, India

The results from stratigraphy, radiocarbon dating and pollen analysis of three salt-lake deposits at Sambhar, Lunkaransar and Didwana in western Raj'asthan, and one freshwater lake deposit at Pushkar in the Aravalli Hills, are described in conjunction with pollen analysis of some archaeological soil samples from the Indus Valley site at Kalibangan in northern Rajasthan. The salt-lake deposits studied are stratigraphically divisible into (a) pre-lacustrine, (b) lacustrine and (c) post-lacustrine sections. The pre-lacustrine section is characterized by a thick bed of aeolian sand underlying lacustrine sediments, while the lacustrine and post-lacustrine sections are broadly circumscribed by laminated clay and nonlaminated silt respectively. The pollen record from the four lake profiles studied is divided into local pollen zones. Four regional pollen assemblage zones are delineated for the area west of the Aravalli Range in Rajasthan. The environmental history deduced from the pollen record is divisible into phases I-V, of which phases II-V follow the regional pollen assemblage zones. Phase I is stratigraphically determined, and is representative of severe arid environments under which the sand dunes, now stabilized, are suggested to have been active. The plant microfossils first appear in phase II with the deposition of lacustrine sediments dated to around 10000 b . p . The vegetation comprises an openland steppe which is rich in grasses, Artemisia and sedges and poor in halophytes. Artemisa, Typha angustata, Mimosa rubicaulis and Oldenlandia , which now grow under areas of comparatively higher average annual rainfall (above 50 cm), appear to have flourished in the semi-arid belt, while the first two plant taxa had encroached even as far as the arid belt, both suggesting that a general westward shift of the rainfall belts had taken place. Vegetation destruction through burning by man is suggested to have started together with the first occurrence of Cerealia-type pollen at about 7500 b . c . and continued thereafter throughout phases III and IV. The increase in swamp vegetation and the intensification of vegetation cover inland together with the maxima of all mesophytic elements in phase IV ( ca. 3000 b .c . to ca. 1000 b .c .) indicate an increase in the rainfall, apart from a short relatively drier time about 1800-1500 b . c . at Sambhar which correlates with the decline of the Indus culture in northwest India. Phase IV is immediately followed by aridity for which there is stratigraphic evidence that the salt lakes started drying. At Pushkar, there is evidence that the vegetation showed a marked change in the Aravallis. The onset of this aridity is suggested to have been widespread. The climate did not ameliorate until about phase V (? early centuries a .d . to present) at which time the Rangmahal culture perhaps flourished in Rajasthan, the remains of which imply good water supply. In conclusion it is suggested that the Rajasthan desert is primarily natural, its history punctuated by at least one more vegetated, humid period during the Holocene, the climatic control of which as indicated by the vegetation history is consistent with climatic events elsewhere in the world.

The Economic, Political and Social Dimensions of an Indian State: A Factor Analysis of District Data for Rajasthan

Rajasthan is a large, unusually diverse state in western India. It has a long frontier with Pakistan, and from north to south touches the adjacent states of Punjab, Haryana, Uttar Pradesh, Madhya Pradesh, and Gujarat. Rajasthan adds to its own internal, social, economic, and political complexity some of the features of each of these disparate neighbors. The dominant geological feature in Rajasthan is the Aravalli range, which runs south to north through the heart of the state. This barrier almost completely arrests the already faltering summer monsoon, creating a semiarid and desert zone to the west and a more watered region in the east.

Some Problems of Precambrian Geology of the Central and Southern Aravalli Range, Rajasthan

Abstract In the Aravalli Range and its environs, the Precambrians consist of the Delhi and the Aravalli systems with the underlying Banded Gneissic Complex (BGC) regarded as the 'Basement Complex' of the region and correlated with the Bundelkhand Gneisses. The unconformity below the Delhis is described as a 'spectacular hiatus', a fact not apparent in the region under review. Portions of the unit mapped as basal conglomerate have been found to be feldspathized mylonites, though there are stretches of basal grits and conglomerates, especially along the northwestern border with the Pre-Delhis. BGC occurs in four patches: (1) N. of the Aravalli metasediments (BGC I), (2) S. of the Aravallis (BGC II), (3) E. of the Aravallis (Berach Granite), and (4) in an oval inlier below the Aravallis, around Serera. The Aravalli-BGC I boundary is diffuse and indefinite, and was obviously unrecognizable north of latitude 25040'. The boundaries of the Aravallis with the BGC II and the Berach Granite are unconformable, so also is the Aravalli-BGC boundary in the Serera inlier. The correlation of Berach Granite and Bundelkhand Gneiss, though deeply entrenched in literature, is only of a tentative nature. The existence of the Raialos seems doubtful. The Delhis show three sets of superposed folds: F1 represented by megascopic folds mainly, and in the complex map pattern at times, is rotated by the immediately following F2 along a coincident or nearly parallel axis; a comparatively open and broad F3 cuts them at high angles producing simple interference in the regional pattern. The nature of the fault between the Delhis and the Pre-Delhis along the eastern border is not clear. No structures could be recognized in the small areas of Aravallis and BGC country studied, that could be regarded as diagnostic of the systems. They show the same structures in the same sequence as found in the Delhis. Search for a diagnostic orogenic trend' in small sample areas is beset with difficulties and may be positively dangerous. Only a detailed and extensive mapping could establish such a feature. The radiometric ages available for rocks of this region are not many. At times contradictory, it is not clear in most of the cases if these 'ages' really date an event to be correlated with the relevant orogeny. A scheme of Precambrian stratigraphy of Rajasthan is proposed, based mainly on the field observations of the author and his associates, and on analysis of published data: Delhi System (1100± to ?750m.y.) Aravalli System = BGCI (I590± to 1000± m.y.) BGC II = BGC (Serera) = ? Berach Granite An attempt has also been made to fit this scheme with the recently proposed classifications of the Precambrians.

The Arthropod Fauna of Sambhar Salt Lake, Rajasthan, India

Lake Sambhar is situated on the east side of the Aravalli range in NW India. It is approximately 350 km2 with an average depth of 0.6 m during the rains. The lake water contains NaCi, Na2SO4, Na2CO3 and NaHCO3 and traces of colloidal CaCO3. It differs from sea water in lacking MgCl2, MgSO4 and KCI. The salinity varies from 9.6 to 164.0%. The dissolved oxygen content is inversely related to salinity and varies from 47.0 mg/l in August to 13.8 mg/l in April. The CO2 as bicarbonate varies from 34.9 mg/l to 135.4 mg/l. The pH shows a seasonal variation from 7.4 to 9.5. Due to the high basicity calcium ions are precipitated. Thus, the environment is very variable throughout the year. There are

Tibet and her Neighbours

T tHERE was a time when a large continent starting from the Aravalli Hills, south of Delhi, extended far beyond the present limits of southern India. To the north of that continent an ocean, which geologists call the Tethys Ocean, extended over the whole of what is now Tibet. Then up-thrusts occurred and the Himalayas and Tibet rose from the bottom of the ocean. In the Himalayan area great twistings and turnings and the action of weather resulted in the further up-thrust of Everest, Kanchenjunga, and other giants of the Himalayan chain, and in the deposition of the material of which the plains of Bengal are formed. To the north there was less disturbance of strata, and it is possible that oil may occur in northern Tibet. Its discovery would bring Tibet into commercial prominence. As the country was rising, glaciers and rivers were cutting their way down across what is now the main Himalayan range towards the plains of India. Perhaps at some future date these river-beds may be used for laying pipe-lines. Lhasa, the capital of Tibet, lies about i2,000 feet above the sea, lower than most of Tibet, which lies about three miles above the sea. But Lhasa is approximately in the same latitude as Delhi, Cairo, and the mouths of the Mississippi. The result is that the climate is not so extreme. as is generally supposed. Most of the country is semi-arid. Northerly winds do not bring rain, and it is only when, in summer, the monsoon cloud is sufficiently established to cross the Himalayan barrier at a height of I5,000 to 25,ooo feet that any considerable amount of rain falls throughout most of Tibet. But under irrigation in central Tibet good crops of wheat grow up to about I4,000 feet, and barley up to i6,ooo feet, and most of the fruits and flowers of an English garden do well in Lhasa. By race and language Tibet is more closely associated with Mongolia and Burma than with China, though she has long had connexions with China and with India. About the fifth or sixth century A.D. Buddhism, which had assumed a Tantric form in India, reached Tibet and, coalescing with the animistic forms of religion which were already established in the country, became the dominant force in the life of a people who previously had had a formidable military reputation. Near Lhasa there are two monasteries of about 8,ooo and 6,ooo monks, and there are many other monasteries, great and small, all over the country. The monasteries own about a third of the cultivated area of Tibet, and there is hardly a family in Tibet which does not contribute a monk or nun to the Church. Religion enters into everybody's daily life. Between Tibet and China also the first close connexion was religious. 71

Regionale Geologie der Erde

DR. G. DE P. COTTER, until recently a superintendent of the Geological Survey of India, has utilized the experience of a lifetime spent in the field in India in summarizing the present state of knowledge of the geology of the peninsula. There are no Palaeozoic rocks there older than the Talchir Boulder Bed at the base of the Gond-wanas, which is regarded, with fair confidence, as Upper Carboniferous. The glaciation was more intense in the south, where ice-scratched rockfloors and boulders occur, whereas in the Himalayas (in Spiti and Kashmir) the representative of the Boulder Bed is a basal conglomerate which may have been deposited by floating bergs. Since India is the only land north of the equator where the Boulder Bed occurs, Cotter is inclined to accept the hypothesis of continental drift and to regard the Indian fragment of Gondwanaland as having drifted northwards from its original home south of the equator, leaving behind it portions of its mass in Madagascar, the Chagos archipelago and the submerged land which forms the platform of the Maldives and Laccadives. Elsewhere the latter is regarded as the extension of the Aravalli Range. Regionale Geologie der Erde Herausgegeben von Karl Andree H. A. Brouwer W. H. Bucher. Band 1, Abschnitt 6: The Indian Peninsula and Ceylon, by G. de P. Cotter. Pp. 66 + vi. (Leipzig: Akademische Verlags-gesellschaft m.b.H., 1938.)