Indrevaer K.,University of Tromsø |
Indrevaer K.,DONG E and P Norge AS |
Stunitz H.,University of Tromsø |
Bergh S.G.,University of Tromsø
Journal of the Geological Society | Year: 2014
Palaeozoic–Mesozoic brittle normal faults onshore along the SW Barents Sea passive margin off northern Norway give valuable insight into fault and fluid flow processes from the lower brittle crust. Microstructural evidence suggests that Late Permian–Early Triassic faulting took place during multiple phases, with initial fault movement at minimum P–T conditions of c. 300 °C and c. 240 MPa (c. 10 km depth), followed by later fault movement at minimum P–T conditions of c. 275 °C and c. 220 MPa (c. 8.5 km depth). The study shows that pore pressures locally reached lithostatic levels (240 MPa) during faulting and that faulting came to a halt during early (deep) stages of rifting along the margin. Fault permeability has been controlled by healing and precipitation processes through time, which have sealed off the core zone and eventually the damage zones after faulting. A minimum average exhumation rate of c. 40 m Ma−1 since the Late Permian is estimated. It implies that the debated Late Cenozoic uplift of the margin may be explained by increased erosion rates in the coastal regions owing to climate detoriation, which caused subsequent isostatic recalibration and uplift of the marginal crust. The studied faults may be used as analogues of basement-involved fault complexes offshore, revealing details about the offshore nature of faulting, including past and present basement and fault zone permeability. © 2014 The Authors.
Indrevaer K.,University of Tromsø |
Indrevaer K.,DONG E and P Norge AS |
Bergh S.G.,University of Tromsø |
Koehl J.-B.,University of Tromsø |
And 3 more authors.
Norsk Geologisk Tidsskrift | Year: 2013
Onshore-offshore correlation of brittle faults and tectonic lineaments has been undertaken along the SW Barents Sea margin off northern Norway. The study has focused on onshore mapping of fault zones, the mapping of offshore fault complexes and associated basins from seismic interpretation, and the linkage of fault complexes onshore and offshore by integrating a high-resolution DEM, covering both onshore and offshore portions of the study area, and processed magnetic anomaly data. This study shows that both onshore and offshore brittle faults manifest themselves mainly as alternating NNE-SSW- and ENE-WSW-trending, steeply to moderately dipping, normal fault zones constituting at least two major NE-SW-trending fault complexes, the Troms-Finnmark and Vestfjorden-Vanna fault complexes. These fault complexes in western Troms bound a major basement horst (the West Troms Basement Complex), run partly onshore and offshore and link up with the offshore Nysleppen and Måsøy fault complexes. Pre-existing structures in the basement, such as foliation, lithological boundaries and ductile shear zones are shown, at least on a local scale, to have exerted a controlling effect on faulting. On a larger scale, at least two major transfer fault zone systems, one along the reactivated Precambrian Senja Shear Belt and the other, the Fugløya transfer zone, accommodate changes in brittle fault polarity along the margin. Our results suggest that distributed rifting during Carboniferous and Late Permian/Early Triassic time was followed by a northwestward localisation of displacement to the Troms-Finnmark and Ringvassøy-Loppa fault complexes during the Late Jurassic/Early Cretaceous, resulting in the formation of a short-tapered, hyperextended margin with final break-up at ~55 Ma. An uplift of the margin and preservation of the West Troms Basement Complex as a basement outlier is suggested to be due to unloading and crustal flexure of the short-tapered margin in the region.
Rydningen T.A.,University of Tromsø |
Rydningen T.A.,DONG E andP Norge AS |
Laberg J.S.,University of Tromsø |
Kolstad V.,DONG E andP Norge AS
Geomorphology | Year: 2015
Trough mouth fans (TMF) situated at the mouths of formerly glaciated cross-shelf troughs are important paleoclimatic archives. Whereas the sedimentary processes of large, low-gradient TMFs have received considerable interest, little attention has been paid to the other end member of this landform class, i.e. TMFs with higher slope gradients. Detailed swath-bathymetric data and seismic profiles from the continental margin offshore Troms, northern Norway cover three high-gradient TMFs (the Andfjorden, Malangsdjupet and Rebbenesdjupet TMFs; slope gradients generally between 1° and 15°), as well as inter-fan areas, which include two submarine canyons (the Andøya and Senja Canyon) and the Malangsgrunnen inter-fan slope. The present-day morphologies of the Andfjorden and Malangsdjupet TMFs have evolved from sediment transport and distribution through gully-channel complexes. The Andfjorden TMF has later been affected by a large submarine landslide that remobilized much of these complexes. The Rebbenesdjupet TMF is dominated by a number of small and relatively shallow slide scars, which are inferred to be related to small-scale sediment failure of glaciomarine and/or contouritic sediments. The canyons cut into the adjacent TMFs, and turbidity currents originating on the fans widened and deepened the canyons during downslope flow. The Malangsgrunnen shelf break and inter-fan slope acted as a funnel for turbidity currents originating on the upper slope, forming a dendritic pattern of gullies. A conceptual model for the high-gradient TMFs on the Troms margin has been compiled. The main sediment input onto the TMFs has occurred during peak glacials when the Fennoscandian Ice Sheet reached the shelf edge. The overall convex fan form and progradational seismic facies show that these glacigenic deposits were repeatedly distributed onto the fan. On the Andfjorden and Malangsdjupet TMFs, gully-channel complexes occur within such deposits. It is thus inferred that the steep slope of these TMFs promoted rapid transformation from small-scale slumps and debris flows on the upper slope, into partly erosive turbidity currents. These flows continued into the deep sea, thus promoting efficient sediment by-pass across the TMFs. This model can be applied to other TMFs situated at the mouths of other glaciated cross-shelf troughs. In contrast, low-gradient TMFs are found to be dominated by glacigenic debris flow deposits. Furthermore, gully-channel complexes demonstrating the presence of erosive turbidity currents on high-gradient TMFs are rare on low-gradient TMFs. Large submarine landslides occur at both high- and low-gradient TMFs. © 2015 Elsevier B.V.
Kusuma M.A.,DONG E and P Norge AS |
Kayatmo A.W.,DONG E and P Norge AS
75th European Association of Geoscientists and Engineers Conference and Exhibition 2013 Incorporating SPE EUROPEC 2013: Changing Frontiers | Year: 2013
Some challenges of velocity model building in a frontier area are the limitation of available well data and sparse seismic data coverage (often only 2D data are available). In the Bjørnøya basin, the wide variation of uplift histories (from 0 to approximately 2000 meters) and overburden thickness also added complexity to the velocity prediction. In order to tackle these challenges, we introduce a new iterative approach of velocity model building that incorporates the density prediction from basin modeling. The density model was built by incorporating burial history, uplift and pressure regime prediction of the area. This density model was then used as a primary guidance for velocity prediction away from the well location. Available seismic velocity was used for QC and comparison purposes. The result of this approach is a velocity model that has a better consistency with our geological knowledge of the area. Copyright © (2012) by the European Association of Geoscientists & Engineers All rights reserved.
Kayatmo A.W.,DONG e and P Norge AS
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014
Exploration in a mature area presents both challenges and rewards. On the one hand, an abundance of data is available, but on the other hand, these data have typically been mined and exploited within familiar exploration contexts. The challenge is to see these data within a new context or applying new methodologies to get a new and better understanding of the area. The combination of detailed quantitative geophysical analysis, at one end of the spectrum, and a broad basin modelling context, at the other end, has provided a novel insight into a mature exploration play in the greater Ula area, Norwegian Southern North Sea. This synthesis not only accounts for the results of past exploration, but opens up possibilities for identifying overlooked potential in one region that was thought to have been maturely explored.