OCCURRENCES OF SANDSTONE SUITABLE AS BUILDING STONE AND FOR CARVING IN BARMER DISTRICT, JODHPURM. S. Sisodia, G. Lashkari & R. G. Goswami*Department of Geology, J. N. Vyas University, Jodhpur. 342 005*Department of Mines and Geology, Government of Rajasthan, Jodhpur.

AbstractSandstone leases have been allotted by the Rajasthan state government in thirteen districts of Rajasthan, but no lease of sandstone to be mined as building stone or for other similar purposes has been allotted in whole of the Barmer district. A few leases allotted in Barmer district are mostly for masonry stone which are of igneous origin and are used as concrete for road construction. We report here new occurrences of sandstone in Barmer Basin, some of these sandstone are thinly bedded, hard, compact, pink colored, fine to coarse grained, quite suitable as building stone; while some are comparatively soft, flaggy, pale to pink colored that can be used for carving etc.

IntroductionThe sedimentary tract in northwestern Rajasthan covers an area of about 1, 20,000 km2. This area is subdivided into several basins viz. The Jaisalmer Basin, the Barmer Basin, the Bikaner-Nagaur Basin and Sanchaur Basin. We mapped Barmer basin basically to deduce the stratigraphy of the Barmer Basin from the available outcrops and to determine tectonic control on basin development from kinematic indicators in the basin fill sediments (see Sisodia and Singh, 2000 for details). The geological map and stratigraphic correlation of Barmer Basin are given in Figs 1and 2. During the survey of Barmer Basin we came across several sandstone outcrops which we reckon as promising areas for building stone. Geology of Barmer Basin The Barmer Basin comprises mainly middle Jurassic to lower Eocene sediments. The outcrops are highly scarce as most of them are covered under extensive desert sand. The oldest rocks exposed in the area belong to the Precambrian Malani Suite of igneous rocks. The formations of Proterozoic to lower Cambrian age named as Birmania and Randha Formations show their presence at the western margin of the basin.Sarnu FormationThe sedimentary rocks overlying the Malani Suite of igneous rocks, with no conformable contact exposed at Sarnu (N25°40.721' E71°46.028') are designated as Sarnu Formation (Dasgupta et al.. 1973 in Panday and Dave. 1998). The Sarnu Formation has very restricted occurrence and does not have wider distribution. The Sarnu Formation is dominantly comprised of sandstone. This sandstone is hard, whitish, silica-cemented quartz arenite with occasional quartz pebbles of 2-5 cm diameter. This sandstone cyclically grades into fine sandstone to siltstone. (Plate 1.a)Barmer Formation:The Barmer Formation is about 70 km thick and extends up to twelve km north of Barmer near Lunu hill. The basal part of the formation comprises reddish, medium to coarse-grained, lithic quartz sandstone and conglomerate. The upper part of the formation is characterized by the presence of siltstone, sandstone and conglomerate (Plate 1.b).Fatehgarh FormationThe sedimentary sequence exposed at Bariyara village (South of Fatehgarh) belongs to the Fatehgarh Formation. The maximum thickness of Fatehgarh Formation is about 71m at Lordi Nala. The formation is a thick sequence of coarsening upward sediments. The major part of

Fatehgarh Formation comprises soft, parallel-laminated, pinkish-white, and fine to medium grained sandstone. The top sandstone shows cross-bedding.

Mataji-ka-Dunger Formation The formation is named after the highest peak (381m), Mataji ka Dungar, near Dharvi Khurd village (N 24038.2’ E 71019.2’). The lithology of the Mataji-ka-Dunger Formation is dominantly sandstone, siltstone, and claystone. The maximum thickness of this formation is about 44m. The formation shows cyclically arranged claystone, siltstone and sandstone. Sandstone shows considerable variation in grain size. However, no distinct mineralogical difference is visible. The grain size variation displays three cycles. The lower cycle at Dharvi Khurd is represented by soft, white, non-calcareous claystone which is overlain by middle- cycle, poorly cemented, thinly bedded, plane-tabular, cross bedded quartz sandstone and siltstone. The upper cycle contains brown to dark brown, hard, granular sandstone.To the NE of Shiv (N 260 06.2’ E 710 12.2’) two outcrops of sandstone are exposed. One type of sandstone is hard, compact, speckled quartzitic sandstone appearing as rhyolite in the rhyolite country. The other type of sandstone is very hard, compact, cherty and displays cross-bedding (Plate 1.c &d).The younger Akli Formation mostly comprises mudstone, bentonite and lignite. The sandstone occurs as intercalations.

Acknowledgement:We are grateful to the local people who acted as guide during our survey of Barmer Basin.

References:Pandey, J. and Dave, A., (1998). Stratigraphy of Indian Petroliferous Basins. Presidential Addresss, XVI Indian Coll. Micropal. Strati., Goa, 247 pp.Sisodia, M. S. and Singh, U. K., (2000). Depositional environment and hydrocarbon prospects of Barmer Basin, Rajasthan, India. Nafta, 51 (9), 309-326

Fig. 1 Geological map of Barmer Basin.

Fig. 2 Stratigraphic correlation of successions of different formations of Barmer Basin.

INDEX

a

b

c d

Plate 1. (a) Sarnu sandstone, it is thinly bedded, pinkish, fine to coarse grained and compact. (b) Soft, fine grained, channel filled Barmer Formation sandstone. (c) Clean, cross bedded sandstone at top of the cycle of Mataji- ka-Dunger Formation.(d) Fine, argillaceous sandstone at Kotra Fort.