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Genesis of evaporite‐associated platform dolomites: case study of the Main Dolomite (Zechstein, Upper Permian), Leba elevation, northern Poland
Author(s) -
PERYT TADEUSZ MAREK,
MAGARITZ MORDECKAI
Publication year - 1990
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1990.tb00632.x
Subject(s) - dolomitization , dolomite , geology , evaporite , diagenesis , permian , geochemistry , facies , carbonate , paleontology , meteoric water , seawater , sedimentary rock , structural basin , hydrothermal circulation , oceanography , materials science , metallurgy
Dolomitization of the Zechstein (Late Permian) Main Dolomite carbonates of northern Poland was penecontemporaneous and/or very early diagenetic. Well‐ordered, stoichiometric dolomites are associated with the basinal facies. The platform dolomites are relatively poorly ordered and usually non‐stoichiometric. Most samples are highly enriched in 13 C, as in other Zechstein carbonates. δ 18 O values show large variations from ‐5·1%0 to + 7·4%. There is an isotope zonation of the examined dolomites. The isotope signature indicates that dolomites formed from variable solutions of meteoric water, seawater, and evaporitic brines of possible marine or continental origin. Once initiated, dolomitization proceeded despite the evolution of dolomitizing brines. This evolution explains the occurrence of lagoonal dolomites with common evidence for dissolution in the lower part of sections compared with well‐developed rhombohedra in the upper part. Crystal zoning suggests the initiation of dolomite growth in hypersaline water and progressive dilution by fresh water. There is isotopic evidence for migration of continental waters into the basin, presumably following sea‐level fall at the end of the deposition of the Main Dolomite. Influence of fresh water on syndepositional dolomitization, well established in the Main Dolomite, strongly suggests that similar relationships may be characteristic for other evaporite‐associated dolomites as well.