| Title | 3D Thermal Effect of Quaternary Erosion and Deposition |
|---|---|
| Authors | Yuriy Petrovich MAYSTRENKO, Leif RISE, Dag OTTESEN, Odleiv OLESEN |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Atlantic Ocean, Europe, thermal modelling, heat flow, continental margin, neotectonics, erosion, deposition |
| Abstract | A 3D subsurface thermal field of the Lofoten segment of the Mid-Norwegian continental margin and adjacent areas of the ocean and continent has been investigated to calculate the thermal influence of late Cenozoic erosion and subsequent deposition of glacial sediments during the Pleistocene. In order to understand the thermal effect of the erosion and deposition, a lithosphere-scale 3D structural model has been constructed based on the available structural data to reveal a deep structure of the Lofoten segment and the northern part of the Vøring segment of the Mid-Norwegian continental margin. This model has been refined by a 3D density modelling and, finally, the gravity-consistent 3D model has been used as a structural base for a 3D thermal modelling, which has been performed by use of commercial software package COMSOL Multiphysics. As an upper thermal boundary condition, a time-dependent temperature at the sea floor and Earth's surface has been taken, considering palaeoclimatic changes during the last two glacial periods. The base of the lithosphere been set as a lower thermal boundary condition which corresponds to the 1300 °C isotherm. In addition to the above-mentioned paleoclimatic scenario, the effect of late Cenozoic erosion and sedimentation has been included during the 3D thermal modelling. Moreover, the 3D thermal modelling has been carried out by considering the thermal effect of early Cenozoic continental breakup. According to the 3D thermal modelling, the thermal effect of the early Cenozoic breakup is still significant in terms of the increased temperatures within the western part of the continental margin and within the oceanic lithospheric domain. Furthermore, the results of the 3D thermal modelling demonstrate that the present-day distribution of the subsurface temperature is characterized by the presence of thermally non-equilibrated zones influenced by the Cenozoic erosion and deposition within the area under consideration. The thermal influence of the erosion shows a positive thermal anomaly within the specific areas where sedimentary and crystalline rocks were eroded. In contrast, a negative thermal anomaly exists in the areas affected by subsidence and deposition. The erosion-induced positive thermal anomaly reaches its maximum of more than +27 ◦C at depths of 17–22 km beneath the eastern part of the Vestfjorden Basin, whereas the most pronounced deposition-induced negative anomaly has a minimum of around −70 ◦C at 17–20 km depth beneath the oceanic Lofoten Basin. In addition, the second negative anomaly has been recognized within the Vøring Basin with values of around −48 ◦C at 12–14 km depth. These pronounced positive and negative thermal anomalies are associated with the regions where erosion and deposition were characterized by relatively high rates during late Cenozoic time. |