DISTRICT SURVEY REPORT OF , TAMILNADU,

INTRODUCTION: with a geographical area of 9,543 sq.km. Is situated in the northwestern part of . It is bounded in the west and north by Karnataka State, in the northeast by Andhra Pradesh and in the eastern part by and districts, in the south by Salem and districts of Tamil Nadu. This district has 8 taluks viz. Dharmapuri, , , Uttangarai, , , Denkanikottai and Palacode. It is one of the backward and drought prone districts of Tamil Nadu.

GEOLOGY : The geological formations of the district belong mainly to Archaean age along with rock of Proterozoic age. The former is represented by Khondalite Group of rocks, Charnockite Group of rocks, Migmatites Complex, Group of rocks, Bhavani Group of rocks and Kolar Group of rocks, while the latter is represented by Alkaline rocks. The Khondalite Group includes garnet sillimanite gneiss and quartzite which occur as small patches. The charnockite Group occupies a major part of southern portion of this district, and it is mainly charnockites along with some small bands of pyroxene granulites and magnetite quartzite. Two small patches of pyroxenite and gabbro are seen to occur in the pyroxene granulite near about 10 km. NE of Harur. The migmatite complex includes garnetiferous quartzofeldspathic gneiss and hornblende biotite gneiss, the former exposed on the western part of the district. The Sathyamangalam Group includes fuchsite quartzite, sillimanite mica schist and amphibolite. The Bhavani Group in this area includes fissile hornblende biotite gneiss, granitoid gneiss and pink migmatite. Amphibolites with banded ferruginous quartzite and associated quartzo-feldspathic rocks (Champion Gneiss) represent the Kolar Group and are found west and southwest of Veppanapalli. Following this there are basic intrusions occurring as dykes.

The Alkaline Complex is represented by epidote-hornblende gneiss, ultramafics, syenite and carbonatite and these are distributed in the eastern part of the district. Innumerable basic dykes and felsite, quartz, barytes and pegmatite veins form part of the Alkali Complex.

MINERAL RESOURCES : A vast range of minerals are reported from this area. They include Apatite, Corundum, Copper, Gold, Iron Ore, Molybdenum, Lead, Limestone, Kankar, Vermiculite and Dimensional Stones. Of them, the gold occurrence in the Veppanapalli area and Molybdenum in Velampatti and its surrounding areas of has been studied in detail. The gold mineralisation in Veppanapalli area is confined to the silicified zones showing gold values between 0.3 and 2.6 g/t. For good dimensional stones, this district is unique in possessing both multicoloured and black granite occurrences. The multicoloured granite named as "Paradiso" is extensively quarried in ChandanpalliSulamalai-Modikuppam-Velampatti belt. The Hosur- Denkanikottai belt is endowed with multicoloured granite deposits. The black granite deposits of Harur, Dharmapuri and Pennagaram taluks are being exported extensively.

GEOMORPHOLOGY AND GEOHYDROLOGY: The district represents a physiographic bridge between the Karnataka, part of the and upland plains of Tamil Nadu and incorporates a part of the Eastern Ghat hills. The western portion of the district between north of Pennayanam and south of Denkanikottai are occupied by the hill ranges of Deccan Plateau trending NNE-SSW. It has a general elevation of 823m to 914m with occassional inselbergs and heights of 1026m, 1219m, 1042m and 1034m. The Deccan Plateau is bounded on the southeast by the trending NE-SW with peaks attaining heights of 1395m, 1059m, 1306m, 1023m. These are mostly structural hills drained by Chinnar, Ponnaiyar and Palar river courses with conspicuous dissection and scarp / retreat. The Eastern Ghats are followed in the east by pediplained upland viz., Tamil Nadu uplands. The upland is an extensive plain studded with a few inselbergs and regions of isolated block mountains such as Shevroy, the Chitteri and the Kalrayan hills. The upland of Dharmapuri has a general elevation of 518 m in the west and 457m in the east and forms a major gap trending NE-SW. The different geomorphic features can be classified as (i) flood plains (ii) pediplain (iii) pediments (iv) residual hills. Major rivers draining the district fall into (i) the Cauvery system and (ii) the Ponnaiyar system. The Chinnar, the Mathalapallam, the Nagavalli and the Toppaiar are the sub basins of the Cauvery system. The Plullampatti Sammandakuppam and Vapniar represent the sub basin of the Ponnaiar system. The Chinnar sub basin covers vast tracks of Denkanikottai and Palacode taluks. The Vaniar sub basin spreads to Harur taluk. The drainage is dendritic in pattern but locally trellis and assymetrical pattern are also seen.

GEOTECHNICAL CHARACTERISTICS AND NATURAL HAZARDS: The area has been demarcated into two engineering geological provinces based on bearing capacity, compressive strength of foundation characteristics of the bed rock geology. There are eight irrigation reservoirs and dams in the area. The proterozoic rocks possess very high bearing capacity and are excellent for foundation, while the Archeans show very high bearing capacity in granites and medium bearing capacity in gneiss.