Structure and evolution of the Bremstein Fault Complex

Abstract

The Bremstein Fault Complex is located on the Mid-Norwegian Continental Margin, where it functions as a boundary zone between the Halten Terrace and the Trøndelag Platform. There has been ongoing activity along the Bremstein Fault Complex since approximately the Middle Triassic, indicated by growth along individual faults. The fault complex was finalized by the downfaulting on the platform-terrace boundary, in the Late Cretaceous, resulting in individual terrace and platform structures. The study focuses on the mechanisms responsible for the structural geometry of the Bremstein Fault Complex, with emphasis on the role of inherited Late Paleozoic structures and reactivated, as well as the extent and control of halokinesis and detachments. Detailed 2D seismic interpretation has been carried out, in order to constrain the timing of faulting and the subsequent structuring. The study area was divided into three segments, each segment represented by a key profile, illustrating the segments main structural style. Four main tectonic events were recorded on the Bremstein Fault Complex: (1) the Permo-Triassic, (2) the Late Triassic-Early Jurassic, (3) the late-Middle Jurassic-Early Cretaceous and (3) the Late Cretaceous-Eocene. The events are evident in the seismic data in the form of structures related to growth faults. The tectonic movement, in the Permo-Triassic is most likely due to pre-existing zones of weakness, related to a Caledonian structural grain. Tectonic activity in the late-Middle Jurassic-Early Cretaceous has resulted in two distinct levels on the Bremstein Fault Complex, based on difference in fault populations and geometries. The evaporite layers functioned as a detachment, dividing the complex into pre-and post-evaporite structural settings.

The Bremstein Fault Complex is located on the Mid-Norwegian Continental Margin, where it functions as a boundary zone between the Halten Terrace and the Trøndelag Platform. There has been ongoing activity along the Bremstein Fault Complex since approximately the Middle Triassic, indicated by growth along individual faults. The fault complex was finalized by the downfaulting on the platform-terrace boundary, in the Late Cretaceous, resulting in individual terrace and platform structures. The study focuses on the mechanisms responsible for the structural geometry of the Bremstein Fault Complex, with emphasis on the role of inherited Late Paleozoic structures and reactivated, as well as the extent and control of halokinesis and detachments. Detailed 2D seismic interpretation has been carried out, in order to constrain the timing of faulting and the subsequent structuring. The study area was divided into three segments, each segment represented by a key profile, illustrating the segments main structural style. Four main tectonic events were recorded on the Bremstein Fault Complex: (1) the Permo-Triassic, (2) the Late Triassic-Early Jurassic, (3) the late-Middle Jurassic-Early Cretaceous and (3) the Late Cretaceous-Eocene. The events are evident in the seismic data in the form of structures related to growth faults. The tectonic movement, in the Permo-Triassic is most likely due to pre-existing zones of weakness, related to a Caledonian structural grain. Tectonic activity in the late-Middle Jurassic-Early Cretaceous has resulted in two distinct levels on the Bremstein Fault Complex, based on difference in fault populations and geometries. The evaporite layers functioned as a detachment, dividing the complex into pre-and post-evaporite structural settings.