Origin and deformation of intra-salt sulphate layers: an example from the Dutch Zechstein (Late Permian)

Biehl, Bianca Coline; Reuning, Lars; Strozyk, Frank; Kukla, Peter A.

doi:10.1007/s00531-014-0999-4

Cited by 22 publications

(16 citation statements)

References 34 publications

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“…This could have been the case above the basement graben below the study area, where subsalt faulting may have produced gentle depressions in the evolving evaporites. Recent studies show that at least some subsalt faults in the study area were active during ZII and ZIII precipitation (Biehl et al, 2014;Strozyk et al, 2014), providing support for this hypothesis. Mg-enriched residual brines are interpreted to have collected inside the depression of the carnallite-rich ZIII1b layers above the basement graben, in the area where the Veendam Pillow later formed, with bischofite precipitation in local lenses (Fig.…”

Section: Sedimentary Architecture and K-mg Salt Depositionsupporting

confidence: 56%

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Evolution of rheologically heterogeneous salt structures: a case study from the NE Netherlands

Raith

Strozyk

Visser³

et al. 2016

Solid Earth

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Abstract. The growth of salt structures is controlled by the low flow strength of evaporites and by the tectonic boundary conditions. The potassium-magnesium salts (K-Mg salts) carnallite and bischofite are prime examples of layers with much lower effective viscosity than halite: their low viscosity presents serious drilling hazards but also allows squeeze solution mining. In contrast, intrasalt anhydrite and carbonate layers (stringers) are much stronger than halite. These rheological contrasts within an evaporite body have an important control on the evolution of the internal structure of salt, but how this mechanical layering affects salt deformation at different scales is not well known. In this study, we use high-resolution 3-D seismic and well data to study the evolution of the Veendam and Slochteren salt pillows at the southern boundary of the Groningen High, northern Netherlands. Here the rock salt layers contain both the mechanically stronger Zechstein III Anhydrite-Carbonate stringer and the weaker K-Mg salts, thus we are able to assess the role of extreme rheological heterogeneities on salt structure growth. The internal structure of the two salt pillows shows areas in which the K-Mg salt-rich ZIII 1b layer is much thicker than elsewhere, in combination with a complexly ruptured and folded ZIII Anhydrite-Carbonate stringer. Thickness maps of supra-salt sediments and well data are used to infer the initial depositional architecture of the K-Mg salts and their deformation history. Results suggest that faulting and the generation of depressions on the top Zechstein surface above a Rotliegend graben caused the local accumulation of bittern brines and precipitation of thick K-Mg salts. During the first phase of salt flow and withdrawal from the Veendam area, under the influence of differential loading by Buntsandstein sediments, the ZIII stringer was boudinaged while the lens of Mg salts remained relatively undeformed. This was followed by a convergence stage, when the K-Mg salt-rich layers were deformed within the inflating salt pillows. This deformation was strongly disharmonic and strongly influenced by folding of the underlying, ruptured ZIII stringer, leading to thickening and internal deformation of the K-Mg salt layers.

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Section: Sedimentary Architecture and K-mg Salt Depositionsupporting

confidence: 56%

“…1; also see Geluk, 2007b;Biehl et al, 2014). The Zechstein section in the study area contains fully developed Z-I to Z-IV cycles.…”

Section: Geological Settingmentioning

confidence: 94%

Evolution of rheologically heterogeneous salt structures: a case study from the NE Netherlands

Raith

Strozyk

Visser³

et al. 2016

Solid Earth

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“…Boudins of thicker layers can thus be longer than those of thinner layers. In layer-parallel shortening of strong layers embedded in a weak matrix, the initial wavelength of the resultant buckle folds increases as the layer thickness increases (Ramberg, 1960;Biot, 1961).…”

Section: Thickness and Strengthmentioning

confidence: 99%

Deformation of intrasalt competent layers in different modes of salt tectonics

Rowan

Urai

Fiduk³

et al. 2019

Solid Earth

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Abstract. Layered evaporite sequences (LESs) comprise interbedded weak layers (halite and, commonly, bittern salts) and strong layers (anhydrite and usually non-evaporite rocks such as carbonates and siliciclastics). This results in a strong rheological stratification, with a range of effective viscosity up to a factor of 105. We focus here on the deformation of competent intrasalt beds in different endmember modes of salt tectonics, even though combinations are common in nature, using a combination of conceptual, numerical, and analog models, and seismic data. In bedding-parallel extension, boudinage of the strong layers forms ruptured stringers, within a halite matrix, that become more isolated with increasing strain. In bedding-parallel shortening, competent layers tend to maintain coherency while forming harmonic, disharmonic, and polyharmonic folds, with the rheological stratification leading to buckling and fold growth by bedding-parallel shear. In differential loading, extension and the resultant stringers dominate beneath suprasalt depocenters, while folded competent beds characterize salt pillows. Finally, in passive diapirs, stringers generated by intrasalt extension are rotated to near vertical and encased in complex folds during upward flow of salt. In all cases, strong layers are progressively removed from areas of salt thinning and increasingly disrupted and folded in areas of salt growth as deformation intensifies. The varying styles of intrasalt deformation impact seismic imaging of LES and associated interpretations. Ruptured stringers are often visible where they have low dips, as in slightly extended salt layers or beneath depocenters, but are poorly imaged in passive diapirs due to steep dips. In contrast, areas of slightly to moderately shortened salt typically have well-imaged, mostly continuous intrasalt reflectors, although seismic coherency decreases as deformation intensifies. Similarly, wells are most likely to penetrate strong layers in contractional structures and salt pillows, less likely in extended salt because they might drill between stringers, and unlikely in tall passive diapirs because the stringers are near vertical. Thus, both seismic and well data may be interpreted to suggest that diapirs and other areas of more intense intrasalt deformation are more halite rich than is actually the case.

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“…Traditionally four carbonate/claystone-evaporite cycles have been described in Germany, known as the Werra (Z1), Stassfurt (Z2), Leine Each cycle represents progressive evaporation with carbonates (Ca) and/or siliciclastics at their base transitioning into anhydrites (A) and topped by thick sequences of salt (Na) and small amounts of potassium and magnesium salts [1,39,41]. The Stassfurt carbonates are therefore abbreviated with Ca2.…”

Section: Geological Backgroundmentioning

confidence: 99%

Dedolomitization Potential of Fluids from Gypsum-to-Anhydrite Conversion: Mass Balance Constraints from the Late Permian Zechstein-2-Carbonates in NW Germany

2018

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The Zechstein-2-Carbonates represent one of the most prolific hydrocarbon systems of Central Europe. Carbonate reservoir quality is primarily controlled by mineralogy, with dolomite representing moderate-to-good porosities and calcite commonly representing low porosities. Current models suggest that this calcite is the result of a basin-wide phase of dedolomitization. The calcium (Ca) source for the dedolomites is thought to be derived from the fluids liberated during gypsum-to-anhydrite conversion. We present an easy-to-use and generally applicable template to estimate the dedolomitization potential of these fluids. Depending on reaction stoichiometry, salinity, and temperature, we estimate that between 2.8 * 10 −3 m 3 and 6.2 * 10 −3 m 3 of calcite may replace dolomite for each m 3 of anhydrite created. Within the constraints dictated by the environment of the late Permian Zechstein basin, we estimate that about 5 * 10 −3 m 3 of dedolomite is created for each m 3 of anhydrite. Mass balance constraints indicate that fluids derived from gypsum-to-anhydrite conversion account for less than 1% of the observed dedolomite in most of the studied industry wells from northern Germany.

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Origin and deformation of intra-salt sulphate layers: an example from the Dutch Zechstein (Late Permian)

Cited by 22 publications

References 34 publications

Evolution of rheologically heterogeneous salt structures: a case study from the NE Netherlands

Evolution of rheologically heterogeneous salt structures: a case study from the NE Netherlands

Deformation of intrasalt competent layers in different modes of salt tectonics

Dedolomitization Potential of Fluids from Gypsum-to-Anhydrite Conversion: Mass Balance Constraints from the Late Permian Zechstein-2-Carbonates in NW Germany

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