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Baskaran, M.
- Mineralogy of Saurashtra Miliolites
Authors
1 Physical Research Laboratory, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 1 (1986), Pagination: 63-89Abstract
The results of CaCO3, carbonate minerals and quartz measurements on 114 miliolites (some of which are dated) and of sedimentatogical and clay mineral studies on select (10-20) samples are reported and discussed.
The miliolite deposits are predominantIy calcite (CaCO3 range = 50.2 to 100 %, mean 86.8 %) with aragonite and quartz as minor components. None of the measured parameters show any trend/pattern between coast and inland which, coupled with field observations indicate that long distance (< 100 Km) eolian transport was unlikely.
Despite the fact that miliolites rest on Deccan trap basalts and several local and Narbada and Tapti river sediments as well as the near coastal sediments of Saurashtra are enriched in clay mineral smectite, the miliolite clays show the dominance of illite which is principally generated by weathering of granites and brought by the Indus river. This observation implies that the processes responsible far bringing Indus clays to Saurashtra region when the miliolites were formed (60 Kyr - 200Kyr) are not operative in recent times.
- The Geochemistry of Uranium and Thorium Isotopes in the Salt Lakes and Adjacent Ground Waters of Rajasthan
Authors
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 1 (1986), Pagination: 90-101Abstract
The concentrations of 238U, 234Th and (234U238U) activity ratios and major ion chemistry of several water samples from the salt lakes and their adjacent ground waters in Rajasthan have been measured. 234Th concentration in all the samples, except in one high alkalinity water from the Sambhar Lake, are quite deficient relative to its parent 238U the average (234Th/238U)activity ratio being 0.12. This deficiency corresponds to a mean residence time of - 5 days for 234Th in these waters. In the high alkalinity water, 234Th concentration is at near equilibrium with 238U, yielding a residence time much longer than radioactive mean life. The long residence time of Th in high alkalinity waters may result from the complexing of 234Th by (CO3)-2 ion. 238U concentration in some of the ground waters near the salt Iakes are high, the highest being in a Didwana sample, 565 dpm/l, The Didwana samples also have the highest (234U238U) activity ratios observed for Indian waters. The high uranium concentration in the Didwana ground water is suggestive of uranium rich aquifer solids.- Geochronology of Miliolite Rocks of Kutch, Western India
Authors
1 Physical Research Laboratory, Ahmedabad 380009, IN
2 KDMIPE, Oil and Natural Gas Commission, Dehra Dun 248195, IN
3 Post-Graduate and Research Institute, Deccan College, Pune 411 006, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 33, No 6 (1989), Pagination: 588-593Abstract
Preliminary geochemical, mineralogical and geochronological studies using 230Th/234U method, of nine rniliolite rocks from Kutch are reported. The Kutch miliolites are characterised by lower CaCO3and higher quartz contents compared to their Saurashtra counterparts. The range of ages for the Kutch and Saurashtra miliolites are same and both can be accommodatedin the 50-70, 75-115 and > 140 K. Yr age groups proposed by Baskaran (1985).The origin of the Kutch miliolites, like those of Saurashtra, appears to be marine. Theories to explain their occurrence in Kutch have to await more detailed studies of this type alongwith ichnological and petrographic observations.
- Clay Mineral Distributions in Dated Miliolites of the Late Quaternary from Saurashtra and Kutch, Gujarat
Authors
1 Physical Research Laboratory, Ahmedabad 380009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 35, No 5 (1990), Pagination: 471-479Abstract
Forty-three dated miliolites (ages ranging from 30-235 kyr) of the late Quaternary period, from Saurashtra and Kutch regions of Gujarat State have been analysed for their detrital contents as well as for the four clay minerals, smectite, illite, kaolinite, and chlorite in the less than 2 micron fraction.
Between 235 kyr and 140 kyr BP. there was less detrital material available in the regions of miliolite formation. Landward and seaward sources, notably from southeast and northwest directions contributed equally efficiently to the clay component of the detritus resulting in illite smectite ratio of 1.0. This situation prevailed during 70-50 kyr BP as well as at around 12 kyr BP except that the total detritus in miliolites increased by a factor of about three, during the two recent periods. However, during 95-115 kyr BP, despite the high detrital content of 24%, the illite/smectite ratio dropped to 0.3 indicating the expected dominance of the local and southeastern sources which are enriched in smectite in their clay fractions.