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KACHCHH PENINSULA AND THE GREAT RANN
The Kachchh Peninsula, located between latitude 23.13°-24.68°N and longitude 68.10°-71.80°E, forms the western most part of India and constitutes the Kachchh district of Gujarat State. Occupying an area of 45,612 sq km, it has length and width extensions of 320 and 170 km, respectively through which passes the Tropic of Cancer. The delta land of Sindh (Pakistan), also known in the olden times by the name Sapta Sindhhu, or the seven distributaries of Indus River, borders it in the west. Its 352 km long southern margin is demarcated by the Gulf of Kachchh, which separates the peninsula from Saurashtra. Its northern margin makes the International border with Pakistan and the eastern abuts Gujarat Mainland. The district has a population of 1,526,321 people inhabiting 949 villages in ten Talukas, population density of 33-persons/sq km, and a total of 466,239 housing units (Source: Census of Housing, GoI, 2001).
 
True colour image of Gujarat and adjoining regions (modified after NASA / GSFC)
 
Geological map of Kachchh District (Modified after DRM, GSI, 2002)
 
The archaeological records reveal that the region was first inhabited by the people of Harappan civilization during 3000-1500 BC. Nearly 60 Harappan culture sites have been discovered in the district, of which, 40 belong to early and the rest to the late phases. Dholavira, which remained occupied for nearly 1500 years in seven distinct stages, is one of the most developed settlements of the Indus people in India. There was a great hiatus in the history of the region between 1400 BC and 500 AD. It is documented that much later, a series of migrations took place from Sindh to Kachchh, and in this process, Sama Rajputs, later known as Jadejas, came to this land and ruled here till the time of India’s independence. The tribes inhabiting the modern Kachchh belong to Sandh, Banni, Rabari (Desi, Dhebaria and Vagadiya), Banjara, Magwar, Samma, Jat, Mutwa and Ahir communities, who are mostly engaged in the professions of agriculture, animal husbandry, handloom, construction work, etc.
Mound of Dholavira, Khadir Island, a 3000-1500 BC Harappan civilization settlement
 
The tectonic evolution of the Kachchh Rift Basin (KRB) dates back to early Mesozoic times, when the Indian landmass was part of the Gondwana Supercontinent. The breaking-off of the Indian subcontinent from the parent mass and its subsequent northward drift owing to fast accretion of more than 16 cm/yr at the Indian Ocean ridge started in Late Triassic. In Late Cretaceous, the subcontinent got detached from Madagascar and, by Early Eocene, separated out from Seychelles. The free drift of the continent was checked during Eocene-Oligocene times, with commencement of subduction of its oceanic crust below the Tibetan plate. By 45-40 Ma, the Neo-Tethys Ocean closed along the Indus-Tsangpo suture, and the collision of the Indian and Tibetan continental crusts began, thereby heralding the rise of the Himalaya. The Indian plate, in its journey beginning from its break-off from the Gondwanaland to its collision with the Asian plate, passed through four plume heads, centered at Crozet, Kerguelen, Marion and Reunion Islands. The Deccan volcanicity, related with the Reunion plume, continued for nearly one million years soon after Maastrichtian age (65 Ma). During extrusion, the Deccan Basalts occupied approximately the same absolute position as that of the Reunion Island; in less than one million years, 1 to 2 million km3 of lava spread out over an area of about 0.5 million km2.
Rifting in the subcontinent along certain Precambrian structural trends started since its detachment from the mainland. In the western margin of the Indian Shield, the faulting was controlled by NE-SW Aravalli-Delhi trend, ENE-WSW Son-Narmada-Tapti (SONATA) trend and NNW-SSE Dharwar trend (Biswas, 1987). Thus, during the migratory history of the subcontinent, three rifted basins, viz, Kachchh, Cambay and SONATA, developed and aborted at different times, became hosts to thick sedimentation of different ages and volcanic activity. The three basins now stand separated by the Saurashtra horst, which has been established to be an extension of the Aravalli range, uplifted in part, during Late Cretaceous times. By Early Cretaceous times, the sea started receding from the KRB, allowing deposition of continental facies. The Mesozoic sediments were deposited in two mega-cycles of i) Late Triassic-Late Jurassic synrift marine transgressive and ii) Late Jurassic-Early Cretaceous post rift deltaic regressive environments. The early part of Tertiary continued to remain terrestrial, but by Early Eocene time, there was marine transgression. The Eocene-Middle Miocene period saw lagoonal, marine shelf to open marine platform type of depositional environment. In Pliocene-Pleistocene times the environment of deposition was littoral to fore shore. Most part of the Quaternary remained terrestrial, with dominance of tidal flat and marsh deposits in the latest part. A pre Holocene period was characterised by desertification in Kachchh. Nagar Parkar, Kachchh Mainland and North Kathiawar faults are recognized as the primordial tectonic discontinuities of the basin with Katrol hill, Gora Dongar, Island Belt, etc. as subsequent generation faults. It is inferred segmented by transverse basement structures following the Dharwar trend, the prominent among them being the Median High.
 
3-D diagrammatic model (not to scale) of Kachchh Rift Basin. NKF: North Kathiawar fault; GDF: Gora Dongar fault; IBF: Island Belt fault; NPF: Nagar Parkar fault (After Pande, 2007).
The Great Rann with pools of liquefaction induced spouted saline water consequent to 2001 Bhuj earthquake.
 
IRS 1D FCC imagery of Central Kachchh. (A) Image dated 4 January 2001 (pre-2001 Bhuj earthquake) of southern margin of Great Rann. (B) Image dated 29 January 2001 (post 2001 Bhuj earthquake) showing extensive spouting of groundwater due to liquefaction.
 
The Kachchh landmass is a central high plateau, which stands dissected in the north, west and east. Its physiographic features, comprising hill ranges, gently sloping peripheral coastal tract, dissected coastal erosional plain fringed successively by younger deltaic plains, tidal flats, spits and marginal accretionary zones, can broadly be divided into four characteristic units, viz, Rann, Banni plains, Hilly tracts and Coastal plains.
The physiographic entity, without any parallel, is the vast expanse of the Rann, a marshy and salt encrusted wasteland, occupying an area of 20,000 sq km. It is the remnant of a very late marine transgression of Miocene Epoch, which is undergoing rapid siltation. This unique landmass occurs in two patches. The northern one, having its northern border with Pakistan and the Thar Desert, is referred to as the Great Rann, which extends in E-W direction for 300 km and has width ranging from 30 to 100 km. The southeast patch, occurring between the Kandla Port in the west and Santalpur in the east, is named as Little Rann. Receding sea level, neotectonic activity and silting by the rivers have been attributed as the causes for the formation and transformation of this landmass, which is remains under the influence of seasonal flooding by precipitation and occasional high tidal waves.
 
Development of a N-S drainage along the Manfara-Kharoi coseismic rupture zone
 
Northern margin of Khadir Island merging with the inundated Great Rann
 
2005 MDA EarthSat Image depicting the characteristic physiographic units and major transverse faults of the central and eastern parts of Kachchh Rift Basin (After Pande, 2007)
 
The Great Rann has a very gentle gradient towards west having the general elevation varying between 3 and 6 m above the mean sea level (msl). Its monotonous relief is broken here and there by small to large patches of higher ground, rising like islands. Some of these are rocky and others, only marginally above the flat plains, are sandy in nature, and support sparse thorny shrubs and grass. These have been referred to as bet or dhoi. One large area of such grassland known as Banni plains lies south of Pachham Island and extends westwards along the north of mainland of Kachchh for a length and breadth of about 80 km and 24 km, respectively. The general elevation of this plain is 6-7 m above the msl. The E-W aligned rocky bets of Pachham, Khadir and Bela Islands stand out prominently amidst the expanse of the Great Rann. In the western most Pachham Island, Pachhmair Pir forms the highest point in the entire Kachchh district, lying at an elevation of 458 m above the msl.
 
A stretch of Great Rann north of Bela-Khadir Islands displaying unblemished white sheets of salt encrustations till the horizon.
The description of the Rann by A.B.Wynne in GSI Memoir Vol.9 on Geology of Kutch (1872) reads, “Its flat unbroken surface of dark silt, baked by the sun and blistered by saline encrustations, is varied only by the mirage, and great tracts of dazzlingly white salt or extensive but shallow flashes of concentrated brine; its intense silent desolation is oppressive, and save by chance a slowly passing caravan of camels or some herd of wild asses even less likely to be seen there is nothing beyond a few bleached skeletons of cattle, salt dried fish, or remains of insects brought down by floods, to maintain a distant and dismal connection between it and life which it is utterly unfitted to support”. Nothing seems to have changed in this great desolate patch of land since this passage was written in 1872 except that it is now much more difficult to wander around with abandon for security reasons.
The Kachchh region presents an interesting case of very recent tectonic adjustments and consequential environmental changes of far reaching anthropo-geographic significance. The great Rann of today was an old inlet of the sea. A river named Puran, a distributory of Indus, formerly flowed across the western Rann to the sea along the Kori Creek, which was navigable from Lakhpat to Ali Bandar in 1808. The records mention of a fertile tract known as Saira bordering Puran river, which, according to Burnes (1835), included the country between Lakhpat and Mundhan. The river in its upstream reaches passed into eastern Nara and this into the bed of Hakra, the lost river of the Indian desert. Fed by Sutlej and some other tributaries, it carried a powerful discharge to the sea. This system of drainage continued to flow between 8th and 16th centuries AD. Later, Sutlej gradually became a part of the Indus system, and by 1798; Hakra was merely a dry channel. The highly diminished flow in Puran was from an effluent of the Indus, over which embankments at Mora and Ali Bandar were constructed. In 1826, by some breach in the banks of Indus, a heavy discharge into the course of Puran swept away all the man-made embankments.
The Kachchh Earthquake of 16 June 1819 had a profound effect in the entire peninsula and brought in some spectacular terrain deformation in the Great Rann. Burnes (1835), in his account of the catastrophe writes, “By the severe shock, hundreds of people perished and every fortified stronghold was shaken to its foundation. Innumerable wells and rivulets were changed from fresh water to salt water. The Brick Fort of Sindhri was overwhelmed at once with a tremendous inundation of water from the Ocean, converting the area into a 25 km long lake”. A remnant of Sindhri lake still exists.
 
2005 MDA EarthSat Image showing the trace of Allah Band and remnant of the Sindhri lake (After Pande, 2007).
 
The redrawn sketches of the Fort (modified after Lyell, 1857), give an idea of the extent of subsidence consequent to the 1819 event. The inhabitants of the Fort are stated to have saved their lives by ascending its walls and sailing to the land the following day by boats. The account also mentions that the inhabitants noticed the presence of a mound of earth 8 km northward of the Fort. It had a length of nearly 25 km and stretched in an E-W direction across a channel of the Indus river, referred to as Pharran or Puran river. The natives called this feature as Allah Band or the bund of God, in allusion to its not being like the other dams in the Indus. It was later assessed that this deformational feature, now referred to as the Allah Band Fault, extended for about 80 km and showed a maximum vertical displacement of 6 m. It is one of the earliest examples, which unequivocally demonstrated that earthquakes had a genetic relationship with rupturing of faults.
 
Redrawn sketches of Sindri Fort (Modified after Lyell, 1857). (a) Sindri Fort in 1808. (b) Sindri Fort in 1838. (c) Sketch section (not to scale) depicting Allah Band uplift and inundation of Sindri Fort consequent to 1819 earthquake (After Pande, 2007)
 
The other characteristic physiographic units of Kachchh are the hilly tracts - intervened by alluvial territories that constitute the Kachchh Mainland and Wagad Land, the coastal zone bordering the Gulf and the mud flats along the various creeks. The groundwater prospects are good in the alluvial fan, valley fill, pediplain and piedmont zones. The district has two thermal springs near Khur and Warna and contains deposits of barites, bauxite, bentonite, kaolinitic clay, glauconite, coal, lignite, limestone, etc (GSI, 2001).
The semi arid land of Kachchh, located south of the Thar Desert, receives an average rainfall of 35 cm per year. The region does not have any perennial river and the development of drainage is poor. Only seasonal rivulets, originating from the central highland, drain the Kachchh region. The south flowing drainages are Naira, Kankawati, Choke, Sie, Vengdi, Kherod, Rukmavati, Khari, Nagwanti, Sakra, etc. The streams flowing to the north of the highland and disappearing in the vast expanse of the Great Rann are Nara, Panjarwati, Chhari, Bhukhi, Tramdo, Kaila, Pur and Kaswali. The drainages of Banas, Saraswati and Rupan rivers, flowing southwesterly through the Mainland Gujarat, debouch into the Little Rann. The northern flowing Machchu, Brahmani and Phulka rivers of Saurashtra also flow into the Little Rann. To utilize the scanty water resources of the district for purposes of drinking and irrigation, 20 medium (reservoir capacity of between 5 and 65 million m3) and 165 minor (reservoir capacity of generally < 4 million m3) dams have been constructed. The important water retention structures include Kaswati, Rudramata, Tapar, Suri, Fatehgarh, Chang and Shivlakha dams. Most of these were damaged by the 26 January 2001 Bhuj Earthquake, and required massive restoration efforts.
 
Source: Burnes, A. (1835). Memoir of the eastern branch of te river Indus giving an account of the alterations produced on it by an earthquake...R. Asiatic Soc. Trans., Vol. 3.
Lyell, C. (1857). Principles of Geology, Eleventh Ed., Appleton & Co. New York. p 834
Wynne, A.B. (1872). Geology of Kutch, Mem. Geol. Surv. India, Vol. 9. p 289
R.D.Oldham (1926). The Cutch earthquake of 16 June 1819 with a revision of great earthquake of 12th June 1897. Mem. Geol. Surv. India, Vol. 47. p 77
Biswas, S.K. (1987). Regional tectonic framework, structure and evolution of the western marginal basins of India. Tectonophysics, Vol. 135. pp 307-327
GSI (2001). Geology and mineral resources of Gujarat, Daman & Diu, Geol. Surv. India Misc. Publ. No. 30, Part XIV. p 102
GSI (2003). Kutch (Bhuj) Earthquake. Geol. Surv. India Spl. Publ. No. 76. p 241
Pande, P. (2007). Evaluation of seismotectonics of Kachchh rift basin, Gujarat, India and assessment of seismic hazard potential of the region. PhD Thesis. p 144

 
 
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