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THE GEOLOGICAL SURVEY OF INDIA.
BANDED GNEISSIC COMPLEX
Gneisses and granites
THE GEOLOGY OF GUJARAT AND SOUTHERN RAJPUTANA. BY B. C. GUPTA AND P. N. MUKERJEE, B.Sc. (CAL.), M.Sc. (LOND.), D.I.C., Asstt. Geologists, Geological Survey of India. (With Plates 1 to 5.)
General description and lithology
Basal conglomerate and quartzite
Relation of the Gneissic Complex to the Aravallis
Quartzite intercalations in the Aravalli schists
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The area with which the following pages are concerned includes in its northern portion the southernmost States of the Rajputana Agency, namely, Dungarpur, Dungarpur, Banswara and Kushalgarh in their entirety and Partabgarh in part. Extending southward the area. covers the eastern tracts of the Mahikantha and Sabarkantha States and Lunavada, Sunth, Sanjeli, Kadana and Balasinor States of the Rewakantha States Agency. Farther south, stretching across the Panch Mahals district and the eastern fringes of Ahmedabad and Kaira districts of the Bombay Presidency, the area includes the Rewakantha States of Bariya and Chhota Udepur. Part of the eastern margin of Baroda State, together with numerous small feudatory States of the Rewakantha States Agency lying north of the Narbada river, forms the southern limit of the area. The western border of the area under
review is fringed by the fertile alluvial plains of Gujarat, while the western margin of the great Malwa plateau flanks it on the east.
The area is nearly 13,000 square miles in extent and lies between the parallels of 22° and 24° north latitude, and 73° and 74° 45′ east longitude.
The geological account of the area which is presented herein is based mainly on two distinct periods of field-work with a hiatus of nearly twenty years between them.
The first was party during the
that of by the Central India and Rajputana years 1907 to 1914 under the superintendence of Mr. C. S. Middlemiss: the late Mr. N. D.
Field-work. Daru was chiefly responsible for the survey of the Southern Rajputana States of Dungarpur and Banswara, and the adjoining Rewakantha States of Sunth and Kadana, while Mr. H. Walker and Dr. A. M. Heron in 1907 and 1908 geologically surveyed the Central Indian State of Jhabua, and Partabgarh and Kushalgarh, the western fringes of which comprise the eastern margin of the area under review.
The second period of field-work, extending over the successive field-seasons between 1931 and 1935, was undertaken by the authors as members of the Rajputana and Bombay party, under the guidance of Dr. A. M. Heron, with a view to extend the previous work of the Central India and Rajputana party southward into the Bombay Presidency.
The intervening period between these two series of field-work has been productive of far-reaching results regarding the succession and correlation of the Archæan formations of Rajputana and its neighbourhood. The authors thus had the advantage of a definite lead in the execution of their own work as well as in the interpretation of the work of their predecessors in the area.
Essentially the area is the southern continuation of the ancient metamorphic regions of Rajputana. The north-western portion of the area represents the south-western extreLinks with surround- mity of the Aravalli range,-much broken and ing areas. ultimately lost in the low-lying alluvial tracts of Gujarat.
Mr. C. S. Middlemiss, in the course of his geological survey of Idar State, surveyed this portion of the area in great detail. His scale of formations, as far as the metamorphic rocks are concerned,
has been reversed as a result of subsequent work establishing connection between his survey and that of Dr. Heron in Rajputana.1 The Phyllite Series of Middlemiss has been found to correspond with the Aravalli phyllites, and his Delhi Quartzite Series is partly the Delhi basement series, the Alwar quartzites, and partly quartzites intercalated in the Aravalli system. Thus interpreted, and greatly generalised, the eastern portion of Middlemiss' geological map of Idar State has been incorporated in the map accompanying this
At its south-western corner the map includes the eastern fringe of R. Bruce Foote's geological map of Baroda2, showing an extensive alluvial area diversified at its north-eastern margin by much worn down heaps of dark Deccan trap.
In the south the map just overlaps the north-western margins of the maps representing the work done by W. T. Blanford in the Taptee and Narbada valleys and P. N. Bose in the lower Narbada valley. The ancient metamorphics are mostly represented by gneissic rocks along this border, except where these are covered by extensive lava piles, the northern continuation of the Deccan trap flows of Rajpipla, mapped and described by P. N. Bose.5
Uninterrupted sheets of extensive lava flows join up the eastern margin of the area with the Malwa plateau, geologically surveyed by H. Walker and A. M. Heron.
Patches of infra-trappeans, often intervening between the ancient metamorphics and the extensive lava flows, have been recorded at several localities in the area under review. These have been correlated with the Bagh beds, the Lameta series and the Nimar sandstones in consideration of their lithological characters and fossil contents.
In the early sixties of the last century W. T. Blanford and A. B. Wynne, in the course of their work in western
Previous observers. India, geologically surveyed portions of the
southern fringe of the area under review.9
1 Rec. Geol. Surv. Ind., LXV, p. 107, (1931), 72, p. (1938).
2 The Geology of Baroda State', by R. Bruce Foote, 1898.
3 Mem. Geol. Surv. Ind., VI, pt. 3, (1869).
4 Op. cit., XXI, pt. 1, (1884).
5 Rec. Geol. Surv. Ind., XXXVII, pt. 2, (1908-1909).
W. T. Blanford, Mem. Geol. Surv. Ind., VI, pt. 3, p. 207, (1869).
7 J. G. Medlicott, Op. cit., II, p. 196 (1860).
8 P. N. Bose, Op. cit., XXI, pt. 1, pp. 3, 23, (1884).
Op. cit., VI, pt. 3, (1869); Rec. Geol. Surv. Ind., V, pt. 3, (1872).
R. Bruce Foote visited the south-western corner of the area in the course of his geological survey of Baroda State, under the auspices of the Baroda Durbar, during 1891 and 1894.1
Sir L. L. Fermor investigated the geology of a portion of the southern tracts of the Panch Mahals district in 1905 in connection with his investigation of the manganese deposits of India.2 His detailed study of the lavas of the Pavagad Hill provides a supplement to Blanford's pioneer work on them.
The north-western corner of the area, composed of the eastern portion of Idar State, was surveyed by C. S. Middlemiss during 1911 and 1916.5
Results of a geological traverse between Pavagad (22° 28′ : 73° 31') and Dohad (22° 50′ : 74° 15′) of the Panch Mahals district, have been recorded by E. J. Beer in the Transactions of the Mining and Geological Institute of India. 6
The north-western tracts of Chhota Udepur State, near the southern end of the area under review, were geologically surveyed by G. V. Hobson during 1923-1924, and described in his paper on "The metamorphic rocks and intrusive granite of Chhota Udepur State".?
Bariya State, adjoining Chhota Udepur on the north, was geologically surveyed by B. Rama Rao during 1930-1931. A report of his work has been published by the Bariya Durbar.8
Dr. P. K. Ghosh, when working in southern Mewar, made a special study of a group of much metamorphosed ultrabasic intrusives occurring in the neighbourhood of Kherwara (23° 59′ 73° 36′). These rocks extend southward across the State boundary into Dungarpur State. The results of Dr. Ghosh's investigations, along with a geological map showing the distribution of these rocks in southern Mewar and Dungarpur, have been published in his paper on the Talc-serpentine-chlorite rocks of southern Mewar and Dungarpur "."