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Palaeoenvironmental changes recorded in the oxygen and carbon isotope composition of Kimmeridgian (Upper Jurassic) carbonates from central Poland

Wierzbowski Henryk

Geological Quarterly

2019

Vol. 63, No. 2

359--374

Oxygen and carbon isotope ratios of well-preserved calcitic bivalves from the Lower-lowermost Upper Kimmeridgian of Central Poland (SW margin of the Holy Cross Mountains) have been studied to reconstruct palaeoenvironmental conditions and variations in ancient water chemistry. Low and scattered δ18O and δ13C values of bivalve shells from shallow carbonate deposits of the Hypselocyclum and the Hypselocyclum-Divisum zone boundary (-3.5 to -1.5, and 2.6 to 4.0‰, respectively) are a result of salinity changes, and local variations in the composition of dissolved inorganic carbon (DIC) in conditions of restricted water circulation. A slight increase in bivalve δ13C values and more densely clustering of δ18O values is observed after the marine transgression at the Divisum-Mutabilis zone boundary. A global decrease of δ13C values of marine carbonates is partly recorded in Lower-lowermost Upper Kimmeridgian bulk carbonates from central Poland (from the Radomsko Elevation and the Wieluń Upland). Local negative shifts and the data scatter are, however, observed in rocks deposited in a very shallow environment of carbonate platforms during the Platynota and Hypselocyclum chrons. This interval corresponds to the uppermost part of the lowstand systems track of a major regressive trend, which had started already in the Late Oxfordian.

Salinity effect on swelling characteristics of compacted bentonite

Shirazi S. M., Wiwat S., Kazama H., Kuwano J., Shaaban M. G.

Environment Protection Engineering

2011

Vol. 37, nr 2

65-74

Swelling characteristics of compacted bentonite is the most important factor for nuclear waste disposal facilities. Salinity effect on swelling behaviour of compacted bentonite was investigated experimentally. A series of one dimensional swelling deformation tests have been performed. The tests were conducted for various initial dry densities from 1.33 g/cm3 to 1.90 g/cm3 for compacted bentonite saturated with NaCl of various concentrations in solution from 0 to 4.0 M. It was found that initial dry density and concentration of NaCl strongly influence the swelling rate of bentonite. The swelling rate of bentonite decreases with increasing the concentration of NaCl. Swelling rate depends on the concentration of NaCl more than on initial dry density and loading effect. Bentonite may change from highly swelled material to coagulate in saline water. Liquid limit of bentonite is also remarkably decreased with the change of liquid from distilled water to saline one, while the plastic limit is slightly increased.