Danian (Paleocene) reefs formed by ahermatypic scleractinian corals in relatively deep water are ... more Danian (Paleocene) reefs formed by ahermatypic scleractinian corals in relatively deep water are known in a few localities in southern Scandinavia. Reflection and shallow seismic profiles, and samples from drilling and scuba diving in bridge pier excavations in Øresund, the strait between Denmark and Sweden, for the first time allow interpretation of the factors that controlled the localisation of the reefs.
Middle-Late Jurassic rifting in East Greenland was marked by westwards tilting of wide fault bloc... more Middle-Late Jurassic rifting in East Greenland was marked by westwards tilting of wide fault blocks bounded by major N-S-trending east-dipping synthetic faults. The syn-rift successions thicken westwards towards the faults and shallow marine sandstones show mainly southwards axial transport directions. An exception to this general pattern is found in south-east Traill Ø, which constitutes the E-tilted Bjørnedal Block, which is bounded to the west by the westwardsdipping antithetic Vaelddal Fault. The stratigraphic development of the Jurassic succession on this block shows important differences to the adjacent areas reflecting a different tectonic development. Shallow marine sand seems initially to have filled accommodation space of the immediately adjacent block to the west. This block subsequently acted as a bypass area and much of the sediment was spilled eastwards onto the hangingwall of the east-dipping Bjørnedal Block. The succession on the Bjørnedal Block shows an eastwards proximal-distal decrease in sandstonemudstone ratio, reflecting increasing water depth and progressive under-filling of the subbasin towards the east in agreement with the dip direction of the fault block. The transverse, mainly south-eastwards palaeocurrents, the eastwards increase in water depths and decrease in sandstone-mudstone ratio on the Bjørnedal Block are at variance with the standard picture of westtilted blocks with southwards-directed palaeocurrents and decrease in grain size. Earlier palaeogeographic reconstructions have to be modified to account for the east-dipping hangingwall and different stratigraphic development of the area. The sea was thus open towards the east and there is no direct indication of a barrier or shoal east of Traill Ø.
d 13 C stratigraphy Calcareous nannofossil biostratigraphy Dinoflagellate biostratigraphy a b s t... more d 13 C stratigraphy Calcareous nannofossil biostratigraphy Dinoflagellate biostratigraphy a b s t r a c t High-resolution carbon isotope stratigraphy of the upper CampanianeMaastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower-resolution d 13 C profile from Rørdal, northwestern Denmark. A quantitative approach is used to test the reliability of Upper Cretaceous nannofossil bio-events and provides accurate biohorizons for the correlation of d 13 C profiles. The CampanianeMaastrichtian boundary (CMB) is identified through the correlation of dinoflagellate biostratigraphy and d 13 C stratigraphy between Stevns-1 and the Global boundary Standard
... The new ammonoid data indicate that deposition was continuous across the Permian–Triassic bou... more ... The new ammonoid data indicate that deposition was continuous across the Permian–Triassic boundary and developed as a marine mudstone–mudstone contact in basinal areas of Hold With Hope, northern and southern Jameson Land. ... 5.c. Northern Jameson Land subbasin. ...
One of the most expanded upper CampanianeMaastrichtian successions worldwide has been cored in a ... more One of the most expanded upper CampanianeMaastrichtian successions worldwide has been cored in a series of boreholes in eastern Denmark. A high-resolution holostratigraphic analysis of this part of the Chalk Group has been undertaken on these cores, notably Stevns-1, in order to provide a record of changes in chalk facies, water depths and sea-water temperatures. Combined lithological data, a suite of petrophysical logs including gamma ray (GR) logs, nannofossil and dinoflagellate palaeontology, stable carbon isotopes, seismic reflection and refraction sections form the basis for the definition of two new formations and six members, three of which are new, and for recognition of Boreal nannofossil subzones UC15e BP to UC20d BP . The upper Campanianelowermost Maastrichtian Mandehoved Formation is subdivided into the Flagbanke and Boesdal Members and the Maastrichtian Møns Klint Formation is subdivided into the Hvidskud, Rørdal, Sigerslev, Kjølby Gaard Marl and Højerup Members. The Boesdal and Rørdal Members show high GR values and a pronounced chalk-marl cyclicity. The Rørdal and the thin Kjølby Gaard Marl Members have a regional distribution and can be traced over most of the Danish Basin, whereas the Højerup Member is restricted to the easternmost part of Sjaelland. The other members consist of rather featureless white chalk.
ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Ste... more ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Stevns Klint (eastern Denmark). The cliff is a world renowned for its spectacular exposure of the Cretaceous-Palaeogene boundary. Based on regional geological knowledge of the field and cores, the characteristics of the Chalk Group have been well constrained. Distinct sedimentary facies have been encountered; the sedimentology, the biostratigraphy, the diagenesis and the reservoir properties have been thoroughly investigated and reported. Stimulated by the intensive geological research, the field studies have been completed with the acquisition of an extensive set of subsurface data. The data include high resolution 2D multichannel seismics onshore and offshore, a seismic refraction profile, two entirely cored boreholes including wireline logs, GPR cross-hole tomography, thermographic analysis, etc. We intend to compile and merge the geological and geophysical datasets to investigate the variation of the Chalk Group properties and their signature in the subsurface. In this communication, the seismic reflection data are being analysed. Very high resolution litho-, bio- and cyclostratigraphy can be correlated with the seismic stratigraphy. Several seismic facies are identified in the Chalk Group: the 'transparent' (white chalk), the stratified (marl-chalk alternations), the crudely stratified (flint-rich chalk) and the hummocky (bryozoan mounds). The units notably vary in thickness at a relatively small scale. The variations confirm the complex shelf organisation which was highly influenced by bottom currents. In addition to the stratigraphic observations, peculiar deformation structures can be recognised. The area has been supposedly tectonically stable since deposition as the coastal cliff lacks fault offset but the succession has been uplifted of c. 1 km. The main fracture patterns are associated with the recent unloading of the ice, opening shallow horizontal fractures. Subvertical fracturation affects also the Chalk and contribute to most of the permeability. Observation of the seismic reflection profiles shows intensive fracturing association with local folds and offsets of reflections reaching 20 metres. The seismic signal is particularly damaged by swarms of fractures which resemble flower structures or polygonal fracture networks. Even if some of the fracture swarms seem to reach the Earth's surface, most of the deformations appear to be restricted to the white chalk, whereas the stratified seismic facies are comparatively less disturbed. The origin of the structures observed in the white chalk can either be associated with the regional stress field or with differential diagenetic evolution between strata inducing anisotropic volume changes. Prediction of the chalk mechanical properties from seismic reflection data is challenging but essential. We believe that improvement in linking lithofacies, fossil content, fracturation regime and diagenesis will improve our general comprehension of the Chalk Sea system but also enhance the accuracy of the geophysical imaging.
ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Ste... more ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Stevns Klint (eastern Denmark). The cliff is a world renowned for its spectacular exposure of the Cretaceous-Palaeogene boundary. Based on regional geological knowledge of the field and cores, the characteristics of the Chalk Group have been well constrained. Distinct sedimentary facies have been encountered; the sedimentology, the biostratigraphy, the diagenesis and the reservoir properties have been thoroughly investigated and reported. Stimulated by the intensive geological research, the field studies have been completed with the acquisition of an extensive set of subsurface data. The data include high resolution 2D multichannel seismics onshore and offshore, a seismic refraction profile, two entirely cored boreholes including wireline logs, GPR cross-hole tomography, thermographic analysis, etc. We intend to compile and merge the geological and geophysical datasets to investigate the variation of the Chalk Group properties and their signature in the subsurface. In this communication, the seismic reflection data are being analysed. Very high resolution litho-, bio- and cyclostratigraphy can be correlated with the seismic stratigraphy. Several seismic facies are identified in the Chalk Group: the 'transparent' (white chalk), the stratified (marl-chalk alternations), the crudely stratified (flint-rich chalk) and the hummocky (bryozoan mounds). The units notably vary in thickness at a relatively small scale. The variations confirm the complex shelf organisation which was highly influenced by bottom currents. In addition to the stratigraphic observations, peculiar deformation structures can be recognised. The area has been supposedly tectonically stable since deposition as the coastal cliff lacks fault offset but the succession has been uplifted of c. 1 km. The main fracture patterns are associated with the recent unloading of the ice, opening shallow horizontal fractures. Subvertical fracturation affects also the Chalk and contribute to most of the permeability. Observation of the seismic reflection profiles shows intensive fracturing association with local folds and offsets of reflections reaching 20 metres. The seismic signal is particularly damaged by swarms of fractures which resemble flower structures or polygonal fracture networks. Even if some of the fracture swarms seem to reach the Earth's surface, most of the deformations appear to be restricted to the white chalk, whereas the stratified seismic facies are comparatively less disturbed. The origin of the structures observed in the white chalk can either be associated with the regional stress field or with differential diagenetic evolution between strata inducing anisotropic volume changes. Prediction of the chalk mechanical properties from seismic reflection data is challenging but essential. We believe that improvement in linking lithofacies, fossil content, fracturation regime and diagenesis will improve our general comprehension of the Chalk Sea system but also enhance the accuracy of the geophysical imaging.
ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Ste... more ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Stevns Klint (eastern Denmark). The cliff is a world renowned for its spectacular exposure of the Cretaceous-Palaeogene boundary. Based on regional geological knowledge of the field and cores, the characteristics of the Chalk Group have been well constrained. Distinct sedimentary facies have been encountered; the sedimentology, the biostratigraphy, the diagenesis and the reservoir properties have been thoroughly investigated and reported. Stimulated by the intensive geological research, the field studies have been completed with the acquisition of an extensive set of subsurface data. The data include high resolution 2D multichannel seismics onshore and offshore, a seismic refraction profile, two entirely cored boreholes including wireline logs, GPR cross-hole tomography, thermographic analysis, etc. We intend to compile and merge the geological and geophysical datasets to investigate the variation of the Chalk Group properties and their signature in the subsurface. In this communication, the seismic reflection data are being analysed. Very high resolution litho-, bio- and cyclostratigraphy can be correlated with the seismic stratigraphy. Several seismic facies are identified in the Chalk Group: the 'transparent' (white chalk), the stratified (marl-chalk alternations), the crudely stratified (flint-rich chalk) and the hummocky (bryozoan mounds). The units notably vary in thickness at a relatively small scale. The variations confirm the complex shelf organisation which was highly influenced by bottom currents. In addition to the stratigraphic observations, peculiar deformation structures can be recognised. The area has been supposedly tectonically stable since deposition as the coastal cliff lacks fault offset but the succession has been uplifted of c. 1 km. The main fracture patterns are associated with the recent unloading of the ice, opening shallow horizontal fractures. Subvertical fracturation affects also the Chalk and contribute to most of the permeability. Observation of the seismic reflection profiles shows intensive fracturing association with local folds and offsets of reflections reaching 20 metres. The seismic signal is particularly damaged by swarms of fractures which resemble flower structures or polygonal fracture networks. Even if some of the fracture swarms seem to reach the Earth's surface, most of the deformations appear to be restricted to the white chalk, whereas the stratified seismic facies are comparatively less disturbed. The origin of the structures observed in the white chalk can either be associated with the regional stress field or with differential diagenetic evolution between strata inducing anisotropic volume changes. Prediction of the chalk mechanical properties from seismic reflection data is challenging but essential. We believe that improvement in linking lithofacies, fossil content, fracturation regime and diagenesis will improve our general comprehension of the Chalk Sea system but also enhance the accuracy of the geophysical imaging.
Danian (Paleocene) reefs formed by ahermatypic scleractinian corals in relatively deep water are ... more Danian (Paleocene) reefs formed by ahermatypic scleractinian corals in relatively deep water are known in a few localities in southern Scandinavia. Reflection and shallow seismic profiles, and samples from drilling and scuba diving in bridge pier excavations in Øresund, the strait between Denmark and Sweden, for the first time allow interpretation of the factors that controlled the localisation of the reefs.
Middle-Late Jurassic rifting in East Greenland was marked by westwards tilting of wide fault bloc... more Middle-Late Jurassic rifting in East Greenland was marked by westwards tilting of wide fault blocks bounded by major N-S-trending east-dipping synthetic faults. The syn-rift successions thicken westwards towards the faults and shallow marine sandstones show mainly southwards axial transport directions. An exception to this general pattern is found in south-east Traill Ø, which constitutes the E-tilted Bjørnedal Block, which is bounded to the west by the westwardsdipping antithetic Vaelddal Fault. The stratigraphic development of the Jurassic succession on this block shows important differences to the adjacent areas reflecting a different tectonic development. Shallow marine sand seems initially to have filled accommodation space of the immediately adjacent block to the west. This block subsequently acted as a bypass area and much of the sediment was spilled eastwards onto the hangingwall of the east-dipping Bjørnedal Block. The succession on the Bjørnedal Block shows an eastwards proximal-distal decrease in sandstonemudstone ratio, reflecting increasing water depth and progressive under-filling of the subbasin towards the east in agreement with the dip direction of the fault block. The transverse, mainly south-eastwards palaeocurrents, the eastwards increase in water depths and decrease in sandstone-mudstone ratio on the Bjørnedal Block are at variance with the standard picture of westtilted blocks with southwards-directed palaeocurrents and decrease in grain size. Earlier palaeogeographic reconstructions have to be modified to account for the east-dipping hangingwall and different stratigraphic development of the area. The sea was thus open towards the east and there is no direct indication of a barrier or shoal east of Traill Ø.
d 13 C stratigraphy Calcareous nannofossil biostratigraphy Dinoflagellate biostratigraphy a b s t... more d 13 C stratigraphy Calcareous nannofossil biostratigraphy Dinoflagellate biostratigraphy a b s t r a c t High-resolution carbon isotope stratigraphy of the upper CampanianeMaastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower-resolution d 13 C profile from Rørdal, northwestern Denmark. A quantitative approach is used to test the reliability of Upper Cretaceous nannofossil bio-events and provides accurate biohorizons for the correlation of d 13 C profiles. The CampanianeMaastrichtian boundary (CMB) is identified through the correlation of dinoflagellate biostratigraphy and d 13 C stratigraphy between Stevns-1 and the Global boundary Standard
... The new ammonoid data indicate that deposition was continuous across the Permian–Triassic bou... more ... The new ammonoid data indicate that deposition was continuous across the Permian–Triassic boundary and developed as a marine mudstone–mudstone contact in basinal areas of Hold With Hope, northern and southern Jameson Land. ... 5.c. Northern Jameson Land subbasin. ...
One of the most expanded upper CampanianeMaastrichtian successions worldwide has been cored in a ... more One of the most expanded upper CampanianeMaastrichtian successions worldwide has been cored in a series of boreholes in eastern Denmark. A high-resolution holostratigraphic analysis of this part of the Chalk Group has been undertaken on these cores, notably Stevns-1, in order to provide a record of changes in chalk facies, water depths and sea-water temperatures. Combined lithological data, a suite of petrophysical logs including gamma ray (GR) logs, nannofossil and dinoflagellate palaeontology, stable carbon isotopes, seismic reflection and refraction sections form the basis for the definition of two new formations and six members, three of which are new, and for recognition of Boreal nannofossil subzones UC15e BP to UC20d BP . The upper Campanianelowermost Maastrichtian Mandehoved Formation is subdivided into the Flagbanke and Boesdal Members and the Maastrichtian Møns Klint Formation is subdivided into the Hvidskud, Rørdal, Sigerslev, Kjølby Gaard Marl and Højerup Members. The Boesdal and Rørdal Members show high GR values and a pronounced chalk-marl cyclicity. The Rørdal and the thin Kjølby Gaard Marl Members have a regional distribution and can be traced over most of the Danish Basin, whereas the Højerup Member is restricted to the easternmost part of Sjaelland. The other members consist of rather featureless white chalk.
ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Ste... more ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Stevns Klint (eastern Denmark). The cliff is a world renowned for its spectacular exposure of the Cretaceous-Palaeogene boundary. Based on regional geological knowledge of the field and cores, the characteristics of the Chalk Group have been well constrained. Distinct sedimentary facies have been encountered; the sedimentology, the biostratigraphy, the diagenesis and the reservoir properties have been thoroughly investigated and reported. Stimulated by the intensive geological research, the field studies have been completed with the acquisition of an extensive set of subsurface data. The data include high resolution 2D multichannel seismics onshore and offshore, a seismic refraction profile, two entirely cored boreholes including wireline logs, GPR cross-hole tomography, thermographic analysis, etc. We intend to compile and merge the geological and geophysical datasets to investigate the variation of the Chalk Group properties and their signature in the subsurface. In this communication, the seismic reflection data are being analysed. Very high resolution litho-, bio- and cyclostratigraphy can be correlated with the seismic stratigraphy. Several seismic facies are identified in the Chalk Group: the 'transparent' (white chalk), the stratified (marl-chalk alternations), the crudely stratified (flint-rich chalk) and the hummocky (bryozoan mounds). The units notably vary in thickness at a relatively small scale. The variations confirm the complex shelf organisation which was highly influenced by bottom currents. In addition to the stratigraphic observations, peculiar deformation structures can be recognised. The area has been supposedly tectonically stable since deposition as the coastal cliff lacks fault offset but the succession has been uplifted of c. 1 km. The main fracture patterns are associated with the recent unloading of the ice, opening shallow horizontal fractures. Subvertical fracturation affects also the Chalk and contribute to most of the permeability. Observation of the seismic reflection profiles shows intensive fracturing association with local folds and offsets of reflections reaching 20 metres. The seismic signal is particularly damaged by swarms of fractures which resemble flower structures or polygonal fracture networks. Even if some of the fracture swarms seem to reach the Earth's surface, most of the deformations appear to be restricted to the white chalk, whereas the stratified seismic facies are comparatively less disturbed. The origin of the structures observed in the white chalk can either be associated with the regional stress field or with differential diagenetic evolution between strata inducing anisotropic volume changes. Prediction of the chalk mechanical properties from seismic reflection data is challenging but essential. We believe that improvement in linking lithofacies, fossil content, fracturation regime and diagenesis will improve our general comprehension of the Chalk Sea system but also enhance the accuracy of the geophysical imaging.
ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Ste... more ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Stevns Klint (eastern Denmark). The cliff is a world renowned for its spectacular exposure of the Cretaceous-Palaeogene boundary. Based on regional geological knowledge of the field and cores, the characteristics of the Chalk Group have been well constrained. Distinct sedimentary facies have been encountered; the sedimentology, the biostratigraphy, the diagenesis and the reservoir properties have been thoroughly investigated and reported. Stimulated by the intensive geological research, the field studies have been completed with the acquisition of an extensive set of subsurface data. The data include high resolution 2D multichannel seismics onshore and offshore, a seismic refraction profile, two entirely cored boreholes including wireline logs, GPR cross-hole tomography, thermographic analysis, etc. We intend to compile and merge the geological and geophysical datasets to investigate the variation of the Chalk Group properties and their signature in the subsurface. In this communication, the seismic reflection data are being analysed. Very high resolution litho-, bio- and cyclostratigraphy can be correlated with the seismic stratigraphy. Several seismic facies are identified in the Chalk Group: the 'transparent' (white chalk), the stratified (marl-chalk alternations), the crudely stratified (flint-rich chalk) and the hummocky (bryozoan mounds). The units notably vary in thickness at a relatively small scale. The variations confirm the complex shelf organisation which was highly influenced by bottom currents. In addition to the stratigraphic observations, peculiar deformation structures can be recognised. The area has been supposedly tectonically stable since deposition as the coastal cliff lacks fault offset but the succession has been uplifted of c. 1 km. The main fracture patterns are associated with the recent unloading of the ice, opening shallow horizontal fractures. Subvertical fracturation affects also the Chalk and contribute to most of the permeability. Observation of the seismic reflection profiles shows intensive fracturing association with local folds and offsets of reflections reaching 20 metres. The seismic signal is particularly damaged by swarms of fractures which resemble flower structures or polygonal fracture networks. Even if some of the fracture swarms seem to reach the Earth's surface, most of the deformations appear to be restricted to the white chalk, whereas the stratified seismic facies are comparatively less disturbed. The origin of the structures observed in the white chalk can either be associated with the regional stress field or with differential diagenetic evolution between strata inducing anisotropic volume changes. Prediction of the chalk mechanical properties from seismic reflection data is challenging but essential. We believe that improvement in linking lithofacies, fossil content, fracturation regime and diagenesis will improve our general comprehension of the Chalk Sea system but also enhance the accuracy of the geophysical imaging.
ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Ste... more ABSTRACT The Upper Cretaceous-Danian chalk is well exposed in the 14 km long coastal cliff of Stevns Klint (eastern Denmark). The cliff is a world renowned for its spectacular exposure of the Cretaceous-Palaeogene boundary. Based on regional geological knowledge of the field and cores, the characteristics of the Chalk Group have been well constrained. Distinct sedimentary facies have been encountered; the sedimentology, the biostratigraphy, the diagenesis and the reservoir properties have been thoroughly investigated and reported. Stimulated by the intensive geological research, the field studies have been completed with the acquisition of an extensive set of subsurface data. The data include high resolution 2D multichannel seismics onshore and offshore, a seismic refraction profile, two entirely cored boreholes including wireline logs, GPR cross-hole tomography, thermographic analysis, etc. We intend to compile and merge the geological and geophysical datasets to investigate the variation of the Chalk Group properties and their signature in the subsurface. In this communication, the seismic reflection data are being analysed. Very high resolution litho-, bio- and cyclostratigraphy can be correlated with the seismic stratigraphy. Several seismic facies are identified in the Chalk Group: the 'transparent' (white chalk), the stratified (marl-chalk alternations), the crudely stratified (flint-rich chalk) and the hummocky (bryozoan mounds). The units notably vary in thickness at a relatively small scale. The variations confirm the complex shelf organisation which was highly influenced by bottom currents. In addition to the stratigraphic observations, peculiar deformation structures can be recognised. The area has been supposedly tectonically stable since deposition as the coastal cliff lacks fault offset but the succession has been uplifted of c. 1 km. The main fracture patterns are associated with the recent unloading of the ice, opening shallow horizontal fractures. Subvertical fracturation affects also the Chalk and contribute to most of the permeability. Observation of the seismic reflection profiles shows intensive fracturing association with local folds and offsets of reflections reaching 20 metres. The seismic signal is particularly damaged by swarms of fractures which resemble flower structures or polygonal fracture networks. Even if some of the fracture swarms seem to reach the Earth's surface, most of the deformations appear to be restricted to the white chalk, whereas the stratified seismic facies are comparatively less disturbed. The origin of the structures observed in the white chalk can either be associated with the regional stress field or with differential diagenetic evolution between strata inducing anisotropic volume changes. Prediction of the chalk mechanical properties from seismic reflection data is challenging but essential. We believe that improvement in linking lithofacies, fossil content, fracturation regime and diagenesis will improve our general comprehension of the Chalk Sea system but also enhance the accuracy of the geophysical imaging.
The genesis of polygonal faults is an intriguing diagenetic phenomenon. This study discusses thei... more The genesis of polygonal faults is an intriguing diagenetic phenomenon. This study discusses their origin in carbonate mudstones together with other associated diagenetic features. In the eastern Danish Basin, at the fringe of the Baltic Sea, the Stevns peninsula offers a unique opportunity to study the early diagenesis of Upper Cretaceous Chalk deposits, buried between 500 and 1400 m. This paper combines data from onshore and offshore high resolution seismic reflection profiles, a fully cored borehole with high resolution wireline logs and quarry and coastal cliff outcrops to study early diagenetic features at different scales. Chalk is affected by an extensive polygonal fault system that is detected in onshore and offshore seismic data. Outcrop and core data provide a better understanding of the distribution of contraction-related features like deformation bands (hairline fractures), stylolites and fluid escape structures. An original model of genetic relationships between these different diagenetic processes is documented for Chalk. The spatial relationships between stylolites and fractures suggest that pressure-solution processes triggered shear failure that initiated the polygonal fault systems. The early diagenetic processes affect the reservoir properties of Chalk by creating compartments and vertical connections. Taking these features into account will allow for a more detailed understanding of early diagenesis and better models for exploiting drinking water or hydrocarbons hosted in Chalk.
Uploads
Papers by Lars Stemmerik