Towards understanding the glacial impact on sedimentary basins using numerical methods
MetadataVis full innførsel
The Cenozoic tectonism and the Pleistocene glaciations had a strong impact on the sedimentary basins and petroleum systems of the Barents Sea. The impact of these processes are often considered together resulting in an unclear understanding of the consequences of each process alone. This thesis focuses on the glacial impact on the sedimentary basins but it also provides an insight about the relative contribution of the glacial and pre-glacial processes to the net erosion, uplift, topography development and depletion of the hydrocarbon traps. Various numerical methods were used in this study. These include a novel approach used for determination of the glacial ages, a new Monte-Carlo-based method for estimating the erosion rates, flexural isostatic and hydrocarbon secondary migration modelling. The main results show that the western Barents Sea was glaciated during four marine isotope stages: MIS 16, MIS 12, MIS 6, and MIS 2, for a total duration of 29 kyr. During the first glacial event the study area was subjected to an erosion of 24.2 ± 8.5 mm/yr. After the first event the rates have significantly changed varying from -12.6 ± 1.6 mm/yr (net deposition) to 1.6 ± 1.8 mm/yr. The results show that in the proximal part of the Bear Island Trough Mouth Fan, the Pleistocene glacial contribution to the total net erosion was small. The most likely glacial contribution in this area reaches 100 ± 90 m, which is about 9% of the total net erosion. In the more distal part of the wedge, the glaciations did not contribute to the net erosion. The pre-glacial relief was modelled close to the sea level with the deepest parts at about 100 - 150 m below sea level and the shallowest at about 300 m above sea level. Between the Early and Middle Pleistocene the relief was deepened by 0 - 200 m. During the Middle-Late Pleistocene the shelf was deepened by up to 300 m in the troughs and up to 100 m on the banks. The Middle Pleistocene shelf represented shallow marine water depths with some elevated parts above the sea level. The model suggests that the inflow of the North Atlantic Current to the Barents Sea was barred by the topography up to ~0.7 Ma. Overall it was found that the contrasting bathymetry of deep troughs and shallow banks was affected by regional isostatic adjustments. The results show that the glacial erosion together with the sea level change caused an isostatic uplift in the range of 250 - 400 m in the troughs and below 200 m on the banks. According to the literature the total uplift magnitude is estimated at about 1 - 2 km so the isostatic component of the uplift is considered to be relatively small. The hydrocarbon trap capacities could have been changed by ± 5 - 14% between the onset of glaciations and the present. The magnitude of capacity change was found to be dependent on tilt values and pre-glacial trap geometry. The western Barents Sea traps with spill points to the west and south at present might have experienced trap capacity increase and were not susceptible to spillage during the Pleistocene, while those with spill points to the east and north might have experienced either volume increase or reduction. Changes of the trap geometry caused by the Pleistocene tilting alone could not have been responsible for any major loss of oil and gas. The tilting together with gas volume expansion might however explain some part of the hydrocarbon loss during the ice ages. It was found that the Pleistocene burial history and tilting cannot be responsible for thick palaeo-oil columns observed in the well cores in the Bjørnøyrenna Fault Complex at the present.
Består avPaper 1: Zieba, Krzysztof Jan; Felix, Maarten; Knies, Jochen. The Pleistocene contribution to the net erosion and sedimentary conditions in the outer Bear Island Trough, western Barents Sea. Arktos 2016 ;Volum 2.(23) s. 1-17 - Is not included due to copyright available at http://dx.doi.org/10.1007/s41063-016-0022-3
Paper 2: Zieba, K.J., Omosanya, K.O., Knies, J., The Pleistocene evolution of the southern Barents Sea bathymetry: a flexural isostasy modelling approach. - Norwegian Journal of Geology Volume The final published version is available at http://dx.doi.org/10.17850/njg97-1-01 © Copyright the authors. This work is licensed under a Creative Commons Attribution 4.0 International License.
Paper 3: Zieba, Krzysztof Jan; Grøver, Arnt. Isostatic response to glacial erosion, deposition and ice loading. Impact on hydrocarbon traps of the southwestern Barents Sea. Marine and Petroleum Geology 2016 ;Volum 78. s. 168-183 http://dx.doi.org/10.1016/j.marpetgeo.2016.09.009 The article in is reprinted with kind permission from Elsevier, sciencedirect.com
Appendix: Emmel, Benjamin; de Jager, Gerben; Zieba, Krzysztof Jan; Kurtev, Kuncho D.; Grøver, Arnt; Lothe, Ane Elisabet; Lippard, Stephen John; Roli, Ole-André. A 3D, map based approach to reconstruct and calibrate palaeobathmetries - Testing the Cretaceous water depth of the Hammerfest Basin, southwestern Barents Sea. Continental Shelf Research 2015 ;Volum 97. s. 21-31 http://dx.doi.org/10.1016/j.csr.2015.02.003 The article in is reprinted with kind permission from Elsevier, sciencedirect.com
Appendix: Zieba, Krzysztof Jan; Daszinnies, Matthias Christian; Emmel, Benjamin; Lothe, Ane Elisabet; Grøver, Arnt; Lippard, Stephen John. Assessment of the Cenozoic Erosion Amount Using Monte Carlo Type-Petroleum Systems Modeling of the Hammerfest Basin, Western Barents Sea. American Journal of Geoscience 2015 ;Volum 4.(2) s. 40-53 http://dx.doi.org/10.3844/ajgsp.2014.40.53 This open access article is distributed under a Creative Commons Attribution (CC-BY) 3.0 license.