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In the Badenian (middle Miocene) basin of the Carpathian foreland of southern Poland, gypsum breccias occur associated with laminated gypsum deposits. These breccias consist of large clasts of gypsum, carbonates, marls and clay chips of variable size embedded in a gypsarenitic matrix. Constituent gypsum grains and clasts commonly appear to be mechanically abraded and chemically corroded crystals or fragments of selenitic, laminated and alabastrine gypsum. Gypsorudites are commonly accompanied by laminated gypsarenites and gypsolutites which show graded bedding; a vertical sequence of graded gypsum beds showing Bouma sequences may be recognized in borehole sections. Microfolding is common within the folded laminated gypsum, and is closely associated with expressions of extensional strain. Both are accompanied by pervasive microfaulting, suggesting a semi-coherent downslope mass movement. The stratiform geometry of the breccias, together with the intensity of slumping relatively independent of the palaeoslope, suggest earthquake shocks as the initial, main cause. Gypsum deposits form a constant, laterally extensive sequence of different lithofacies. The occurrence of the same lithologies and shallowing-up cycles over a wide area reflects thrusting of the Carpathians over the Carpathian foredeep. Local tectonism has also played a significant role. The tectonic framework favoured activation of dip-slip faults promoting shallow-focus earthquakes. These in turn resulted in the resedimentation of gypsum by slumps, debris flows and turbidites. A similar basinward resedimentation of clastic material by gravity flows initiated by fault-induced earthquakes could be of great importance in the foreland geological setting, and may explain some phenomena observed in other evaporite formations from different geological settings, especially of rift type. 相似文献
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Origin of polyhalite deposits in the Zechstein (Upper Permian) Zdrada platform (northern Poland) 总被引：1，自引：0，他引：1
Polyhalite deposits in the Zechstein (Upper Permian) of northern Poland occur in the Lower Werra Anhydrite. In the Zdrada Sulphate Platform, the polyhalite appears to be a very early replacement of anhydrite. The replacement was caused by the halite-precipitating brines which contained potassium and magnesium ions. The formation of polyhalite was preceded by the syndepositional anhydritization of the original gypsum deposit which has often preserved its primary textures. This anhydritization on the platform and its slopes was a reaction of the precipitated gypsum in a hydrologically open evaporite basin, with brines of salt basins adjacent to the sulphate platform. These brines, when nearly saturated with respect to halite, and potassium and magnesium rich, reacted with anhydrite to precipitate polyhalite along the slopes of the Zdrada Platform. The oxygen and sulphur isotopic compositions of sulphate evaporites indicate that marine solutions were the only source of sulphate ions supplied to the Zechstein basin, and that anhydrite was transformed to polyhalite by reaction with marine brines more concentrated than those that precipitated precursor calcium sulphate minerals. 相似文献
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TADEUSZ MAREK PERYT 《Sedimentology》1996,43(3):571-588
Primary gypsum is the main evaporite mineral in the middle Miocene (Badenian) of the West Ukraine. The lower part of the gypsum sequence is built of autochthonous gypsum while the upper part is composed of allochthonous gypsum that formed following a major, tectonically induced, change in basin morphology. This change resulted in the destruction of the gypsum deposited on the margins of the basin and formation of redeposition features. Autochthonous gypsum facies were deposited in two main environments: (1) giant gypsum intergrowths precipitated from highly concentrated brines; (2) very shallow subaqueous gypsum deposited in a vast brine pan. The brine pan was characterized by a facies mosaic that reflects an interplay of concentrated brines from the central part of the evaporite basin and diluted brines due to the influx of continental meteoric waters. The facies continuum, microbial gypsum - bedded selenite - massive selenite - sabre gypsum, indicates increasing salinity of the brine with time. This type of facies pattern has been established in recent salinas that are analogous to Badenian gypsum in their lateral facies changes. However, the pattern of facies distribution with respect to the open sea in the Badenian basin is opposite to that found in recent salinas. The pattern of the Badenian gypsum facies in the Ukraine indicates that facies repetition may have been related to climatically controlled salinity changes and not to depth changes, as is commonly used to explain the repetition of sulphate facies in a vertical succession. 相似文献
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The Zechstein Basin of Poland was an area of widespread cyclical deposition of carbonates and evaporites during Late Permian time. The Zechstein shelves, along both the northern and the southern margins of the basin, were sites of shallow-water sedimentation during the formation of the Main Dolomite and Platy Dolomite, two widespread carbonate units. These units consist of oolitic, peloidal, skeletal, micritic and evaporitic carbonates formed in depositional settings ranging from open marine to coastal (lagoonal, sabkha and salina). Although originally deposited as limestones, the Main Dolomite and Platy Dolomite are inferred to have been completely replaced by dolomite through very early stage (essentially penecontemporaneous) reflux of hypersaline brines. The dolomites of the two basin margins, however, have very different petrographic and isotopic characteristics. Many northern shelf dolomites show early stage calcitization (dedolomitization) and even, in some cases, evidence of a subsequent redolomitization event. These northern shelf samples also have a broad range of carbon and oxygen isotopic ratios (up to 12%0 for oxygen). Samples from the southern shelf, on the other hand, are petrographically much simpler; they do not show complex calcitization and redolomitization patterns. Likewise, their isotopic values are much more tightly clustered, with only about a 5%0 range of oxygen isotopic ratios. The differences between dolomites of the same age from the northern and southern margins are best explained by regional variations in river water influx during episodic exposure events associated with regional or global sea-level fluctuations. The distribution of clastic terrigenous materials and palaeokarstic features indicate that areas of the northern shelf had extensive river input, an influx largely lacking on the southern shelf. Early formed dolomites appear to have been calcitized during sea-level lowstands through the infiltration of meteoric fluids into the evaporitic dolomites created during the previous highstand. In some cases, redolomitization occurred when meteoric fluids were again replaced by hypersaline brines during subsequent sea-level highstands. Although repeated sea-level fluctuations are clearly evident in these strata, it is likely that associated climatic changes (rainfall variations) also played a role in forming these complex diagenetic patterns. Age-equivalent strata from Texas and New Mexico (from sites at much lower palaeolatitudes) show no such alteration patterns; samples from Greenland (slightly higher palaeolatitudes) show even more intense diagenetic alteration during depositional cycles. Thus, the examination of patterns of diagenesis may be useful in interpreting ancient, palaeolatitudinally sensitive climate patterns. 相似文献
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TADEUSZ MAREK PERYT 《Sedimentology》1994,41(1):83-113
The Lower Werra Anhydrite (Zechstein, Upper Permian) deposits of the teba area originated in a deep basin setting, in shallow to deep water conditions. Facies changes occur within small distances and suggest fluctuating boundaries between well defined basins and platforms. This pattern of local platforms and adjacent basins developed during deposition. In basinal areas, the sequence is clearly transgressive, whereas on platforms accumulation kept pace with subsidence after an initial transgression. Nodular anhydrite represents a polygenetic deposit which formed at different times with respect to deposition. Massive anhydrite with pseudomorphs after upright-growth gypsum crystals suggest rapid precipitation in a subaqueous environment and/or fluctuating, but generally high, salinity conditions. Massive clastic sulphate originated due to periodic high energy events and resedimentation, or due to brecciation possibly connected with salinity fluctuations and the dissolution of halite. Massive, textureless anhydrite is locally porous and passes upward into breccia, indicating a strongly saline environment. Bedded anhydrite is considered to form in shallow water environments and laminated anhydrite in deep water. Bedded anhydrites contain portions which are graded. Intercalations of sulphate turbidites and upright-growth gypsum suggest fluctuating water depths, with comparatively deep water during turbidite deposition, but shallower conditions during upright-growth gypsum deposition. The sequence observed in slope zones at platform-basin margins, detrital (parautochthonous) sulphate sand to graded beds to basinal laminites, indicates that redistribution processes were important. At the onset of the Lower Werra Anhydrite deposition bathymetric relief existed between the central part of the basin and its margins, where carbonate platforms remained subaerially exposed. Formation of local platforms and adjacent basins required a relatively high subsidence rate, as pre-existing relief cannot account for the total accumulated thickness of the Lower Werra Anhydrite deposits. One implication of this is that the main argument against ‘the shallow water - shallow basin’ evaporite basin model, i.e.,a very fast rate of subsidence, may not be valid for the Łeba Lower Werra Anhydrite basin. 相似文献
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T. M. PERYT A. HOPPE T. BECHSTÄDT J. KÖSTER C. PIERRE D. K. RICHTER 《Sedimentology》1990,37(2):279-286
The Late Proterozoic Pedro Leopoldo facies (Bambuí Group) in the vicinity of Belo Horizonte, Brazil, comprises alternating laminated microsparitic limestones (10–35 mm thick beds) and fibrous limestones (10–55 mm thick). The latter are composed of a mosaic of sparry calcite crystals. These irregularly crosscut rays and fans are composed of feathery precursor crystal bundles with squared-off growth zones. Ghosts of an original fibrous mineral, hexagonal in cross-section, are visible. The petrographic characteristics, very high strontium content and low magnesium content of the fibrous beds, as well as microspar beds, strongly argue for an original aragonitic mineralogy. The rays are interpreted as having formed by precipitation at the sediment-water interface, whereas the micrite was precipitated from the water column prior to deposition on the sea floor. The lack of emergence features suggests widespread aragonite precipitation under persistently subtidal conditions. 相似文献
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Genesis of evaporite-associated platform dolomites: case study of the Main Dolomite (Zechstein, Upper Permian), Leba elevation, northern Poland 总被引：1，自引：0，他引：1
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 13C, as in other Zechstein carbonates. δ18O 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. 相似文献
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