The “schizohaline” environment: Its sedimentary and diagenetic fabrics as exemplified by Late Paleozoic rocks of Bear Island,Svalbard |
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| Authors: | Robert L Folk Anna Siedlecka |
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| Institution: | 1. Department of Geological Sciences, University of Texas at Austin, Austin, Texas U.S.A.;2. Norges Geologiske Undersøkelse, Trondheim Norway |
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| Abstract: | Environments characterized by fluctuating hypersaline to fresh-water conditions are defined as “schizohaline” and examples are given of situations in which “schizohaline” environments can arise. Fabrics diagnostic for the occurrence of both hyper- and hyposalinity have been recorded in Late Paleozoic rocks from Bear Island (74°30′N, 19°E): evaporite nodules, length-slow chalcedony and very finely crystalline penecontemporaneous dolomite are considered as indicators of hypersaline conditions while euhedral limpid dolomite crystals, coarse poikilitic sparry calcite and microspar calcite are thought to have originated under the hyposaline regime. Zoned dolomite crystals and euhedral crystals of authigenic mega-quartz replacing sulphates have also been recorded in the same rocks; their diagnostic importance for the schizohaline environment is, however, uncertain.Internal structural pores of some crinoid and bryozoan skeletal grains of biosparites from Bear Island are either empty or infilled with very finely crystalline dolomite. Expulsion of Mg2+ ions from the magnesian-calcite skeletons and either: (1) “poisoning” of the micro-environment of the pores; or (2) formation of stagnant “micro-sabkha” conditions in the pores are proposed as an explanation for these phenomena. |
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