No abstract

The DOBRE project investigated the interplay of geologic and geodynamic processes that controlled the evolution of the Donbas fold belt, Ukraine, as an example of an inverted intracratonic rift basin. A deep seismic reflection profile provides an excellent image of the structure of the Donbas fold belt, which is the uplifted and compressionally deformed part of the late Paleozoic Pripyat-Dniepr-Donets basin. Both the effects of rifting and those of later structural inversion are recognized in the seismic and geologic data. The interpretation of the reflection data shows that the inversion of the Donbas fold belt occurred at the crustal scale as a mega-pop-up, which involved a major detachment fault through the entire crust and an associated back thrust. The DOBREflection image provides a simple concept of intracratonic basin inversion, the crustal pop-up being uplifted and internally deformed. The association of such a structure with inverted intracratonic basins such as the Donbas fold belt implies brittle deformation of relatively cold crust.

The salt tectonics of the Glueckstadt Graben has been investigated in relation to major tectonic events within the basin. The lithologic features of salt sections from Rotliegend, Zechstein and Keuper show that almost pure salt is prominent in the Zechstein, dominating diapiric movements that have influenced the regional evolution of the Glueckstadt Graben.

To understand the major structural features of the sedimentary cover and crystalline crust of the Lofoten‐Vesterålen margin and the northern part of the Vøring segment of the Mid‐Norwegian continental margin, a lithosphere‐scale 3‐D structural model has been constructed. This model extends from the exposed crystalline rocks of the Fennoscandian Shield in the east to the Cenozoic oceanic domain of the Norwegian‐Greenland Sea in the west, covering the Vestfjorden, Ribban, and Røst Basins and the northern parts of the Vøring Basin and Trøndelag Platform. All available published and/or released data have been used to set the initial 3‐D model which has been validated by means of 3‐D density forward modeling to obtain a gravity‐consistent 3‐D structural/density model. Results from the 3‐D density modeling reveal that relatively thick sedimentary rocks are present in the distal Røst Basin below the lava flows. The presence of a low‐density more than 20 km thick granitic body has been modeled within the middle‐upper crystalline crust beneath the eastern part of the Vestfjorden Basin and the adjacent mainland. Moreover, the results of the 3‐D density modeling indicate the presence of an atypical low‐density lithospheric mantle beneath a large part of the Lofoten‐Vesterålen margin which is required to fit the regional component of the modeled gravity with the observed one. The pronounced crustal feature within the model area is the Bivrost Lineament that appears to be the deeply seated lithosphere‐scale boundary that delineates clearly the Lofoten‐Vesterålen segment from the Vøring margin showing contrasting densities and crustal thicknesses.

No abstract

No abstract

The deep structure of the northern North Sea and the adjacent Norwegian mainland has been analysed by integrating all available structural data in combination with 3D density and magnetic modelling into a lithosphere-scale 3D structural model. The modelled configurations of the sedimentary cover and crystalline crust are consistent with the long-wavelength components of the observed gravity and magnetic fields over the study area. The first-order configurations of the top of the crystalline basement and the Moho topography have been obtained. According to the 3D density modelling, the low-density upper-crustal block beneath the Horda Platform has been shown to indicate a possible presence of metasedimentary and/or fractured granitic rocks. Possible remnants of island arc chains within the central part of the North Sea between the Laurentian and Baltican crustal domains are supported by the modelling. Moreover, based on the results of the 3D magnetic modelling, the 3D density/structural model has been differentiated into smaller crustal blocks with different magnetic properties, implying that these magnetically derived crustal blocks most likely differ lithologically from the rest of the initial density-based larger layers. Within the mainland, most of the crustal blocks with increased magnetic susceptibility are related to granitic and/or granodioritic rocks which are well mapped at the surface according to geological data. A prominent middle-upper crustal magmatic intrusion has been modelled within the northern part of the NorwegianDanish Basin. The local magnetic pattern supports a possible Permian age for this intrusion, whereas the regional magnetic pattern and known geology from the mainland indicate a Sveconorwegian origin as a more viable alternative. At the mantle level, a low-density lithospheric mantle has been modelled beneath NW Norway and adjacent offshore areas, reflecting the likely presence of an upper-mantle low-velocity zone there.

No abstract