06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation
06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation
06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation
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Gulf of Kachchh<br />
Table 5 : Natural wealth of coastal area of Gulf of Kachchh<br />
District Metallic Non-metallic Economically<br />
minerals minerals useful rocks<br />
Kachchh Bauxite Agate,Bentonite, Limestone,<br />
Fireclay,Ochres sandstone<br />
Jamnagar Bauxite Chalk,Gypsum, Limestone<br />
Quartz,Silica-sand<br />
Source: AfehJ; 1995<br />
ii. Geomorphology<br />
The northern plank of the Gulf Le. area from<br />
Jakhau to Kandla has irregular and dissected<br />
configurations. The western half, overlooking the<br />
open Arabian Sea, trends NW-SE and is<br />
dominantly muddy and made up of extensive tidal<br />
fiats. The E-W trending coast that lies inside the<br />
Gulf of Kachchh, is sandy and silty with narrow<br />
beaches. It merges with the Little Rann to the<br />
east. However, the southern plank of the Gulf Le.<br />
the area from Navlakhi to Dwarka, trending E-W,<br />
overlooks the Gulf and shows a crenellated rocky<br />
shoreline with the subtidal zone consisting of<br />
channels, shoals, submerged islands, sand bars,<br />
coral reefs and mangroves.<br />
The beach sands are calcareous and dominated by<br />
bio-casts. The consolidated ancient equivalents of<br />
these biogenic sands are the famous miliolite<br />
rocks. The minerological and petrographical<br />
studies of the submerged intertidal rocks of the<br />
Gulf of Kachchh indicate that they are calcareous<br />
sandstones. The petrology of the rocks, study of<br />
the foraminifera and the nature of insoluble<br />
residue, suggest that these rocks were formed in<br />
an intertidal region of deposition during a period<br />
of lowered sea level (Hashmi et al., 1977).<br />
The Rann is the most remarkable and unique<br />
feature of the Kachchh region, occupying its<br />
northern and eastern parts, forming more than<br />
half of the aerial extent of Kachchh. Mehr & Malik<br />
(1996) give specific account of the formation of<br />
Little Rann (falling between 23'10'N to 23'45'<br />
latitudes and 70'45'E to 71'45'E longitudes) and<br />
owe its origin to the transgression through the Gulf<br />
of Kachchh. According to them the Little Rann<br />
represents the former extension of the Gulf of<br />
Kachchh when the sea:level was high during the<br />
last Holocene transgression.<br />
a. Bathymetry :<br />
The sea slopes gently towards west from the<br />
Arabian sea coast of Kachchh. The sea bed is<br />
Mineral tuels<br />
The tides are of mixed semi-diurnal type (M, type),<br />
with a large diurnal inequality and varying<br />
amplitude, which decreases from north to south<br />
along both the coasts. Because of unique position,<br />
nearness to the Tropic of Cancer, funnel shape of<br />
the Gulf and resonance effects, it experience very<br />
high tides, roughly the highest anywhere along the<br />
Indian coast. The tides, in general, are low on the<br />
open Arabian sea near the Gulf of Kachchh. The<br />
mean high-water spring (MHWS) of 3.47m in Okha<br />
increases to 5.36m at Sikka to 7.31m at Navalakhi.<br />
Longshore currents with low wave energy<br />
dominate the open coasts along the Arabian Sea.<br />
The tidal currents dominate the fiow in Gulf of<br />
Kachchh. Maximum velocities occur during midtide,<br />
which is around 4 knots, associated with high<br />
wave energy.<br />
During the SW monsoon the coastal surface<br />
currents along the West Coast of Saurashtra fiow<br />
alongshore directed northwards. At a distance of<br />
3-5 km from the coast the alongshore current<br />
develops a shoreward component. This<br />
phenomenon is reverses during NE monsoon when<br />
the alongshore-current fiow equator-wards and its<br />
perpendicular component gets directed away from<br />
the shore.<br />
The currents in the Gulf though tidal, are monsoon<br />
in origin. The flow adjusts its directional<br />
orientation with the changing dire( .ion of the wind<br />
affected by changing seasons of the year.<br />
iii. Climate<br />
mostly sandy and muddy. This is<br />
caused by the prograding sediment<br />
from the Indus delta.<br />
Lignite Depth of the Gulf of Kachchh ranges<br />
from a maximum of about 60m at the<br />
mouth to less than 20m at the head of<br />
the Gulf. The topography is very<br />
irregular at the mouth and the central<br />
part of the Gulf and consists of pinnacles and<br />
scarps ranging in height from 6 to 32 m. towards<br />
the head the relief is subdued due to the covering<br />
of fine-grained sediment.<br />
4<br />
b. Tides and currents :<br />
The climate in the coastal area of the Gulf of<br />
Kachchh is arid to semi-arid. The northern plank<br />
is extreme arid while southern plank shows semiarid<br />
climate. The .climate is very dryas the<br />
rainfall is always below average every year, which