TY - JOUR A1 - Noack, Vera A1 - Scheck-Wenderoth, Magdalena A1 - Cacace, Mauro T1 - Sensitivity of 3D thermal models to the choice of boundary conditions and thermal properties: a case study for the area of Brandenburg (NE German Basin) JF - Environmental earth sciences N2 - Based on newly available data of both, the structural setting and thermal properties, we compare 3D thermal models for the area of Brandenburg, located in the Northeast German Basin, to assess the sensitivity of our model results. The structural complexity of the basin fill is given by the configuration of the Zechstein salt with salt diapirs and salt pillows. This special configuration is very relevant for the thermal calculations because salt has a distinctly higher thermal conductivity than other sediments. We calculate the temperature using a FEMethod to solve the steady state heat conduction equation in 3D. Based on this approach, we evaluate the sensitivity of the steady-state conductive thermal field with respect to different lithospheric configurations and to the assigned thermal properties. We compare three different thermal models: (a) a crustal-scale model including a homogeneous crust, (b) a new lithosphere-scale model including a differentiated crust and (c) a crustal-scale model with a stepwise variation of measured thermal properties. The comparison with measured temperatures from different structural locations of the basin shows a good fit to the temperature predictions for the first two models, whereas the third model is distinctly colder. This indicates that effective thermal conductivities may be different from values determined by measurements on rock samples. The results suggest that conduction is the main heat transport mechanism in the Brandenburg area. KW - Conductive thermal field KW - 3D thermal model KW - Lithosphere-asthenosphere boundary KW - Zechstein salt KW - Brandenburg KW - Northeast German Basin Y1 - 2012 U6 - https://doi.org/10.1007/s12665-012-1614-2 SN - 1866-6280 VL - 67 IS - 6 SP - 1695 EP - 1711 PB - Springer CY - New York ER - TY - JOUR A1 - Balling, Philipp A1 - Maystrenko, Yuriy A1 - Scheck-Wenderoth, Magdalena T1 - The deep thermal field of the Glückstadt Graben JF - Environmental earth sciences N2 - With this paper, we assess the present-day conductive thermal field of the Glueckstadt Graben in NW Germany that is characterized by large salt walls and diapirs structuring the graben fill. We use a finite element method to calculate the 3D steady-state conductive thermal field based on a lithosphere-scale 3D structural model that resolves the first-order structural characteristics of the graben and its underlying lithosphere. Model predictions are validated against measured temperatures in six deep wells. Our investigations show that the interaction of thickness distributions and thermal rock properties of the different geological layers is of major importance for the distribution of temperatures in the deep subsurface of the Glueckstadt Graben. However, the local temperatures may result from the superposed effects of different controlling factors. Especially, the upper sedimentary part of the model exhibits huge lateral temperature variations, which correlate spatially with the shape of the thermally highly conductive Permian salt layer. Variations in thickness and geometry of the salt cause two major effects, which provoke considerable lateral temperature variations for a given depth. (1) The "chimney effect" causes more efficient heat transport within salt diapirs. As a consequence positive thermal anomalies develop in the upper part and above salt structures, where the latter are covered by much less conductive sediments. In contrast, negative thermal anomalies are noticeable underneath salt structures. (2) The "thermal blanketing effect" is caused by thermally low conductive sediments that provoke the local storage of heat where these insulating sediments are present. The latter effect leads to both local and regional thermal anomalies. Locally, this translates to higher temperatures where salt margin synclines are filled with thick insulating clastic sediments. For the regional anomalies the cumulative insulating effects of the entire sediment fill results in a long-wavelength variation of temperatures in response to heat refraction effects caused by the contrast between insulating sediments and highly conductive crystalline crust. Finally, the longest wavelength of temperature variations is caused by the depth position of the isothermal lithosphere-asthenosphere boundary defining the regional variations of the overall geothermal gradient. We find that a conductive thermal model predicts observed temperatures reasonably well for five of the six available wells, whereas the steady-state conductive approach appears not to be valid for the sixth well. KW - Conductive thermal field KW - 3D thermal modelling KW - Zechstein salt KW - Lithosphereasthenosphere boundary KW - Schleswig-Holstein KW - Glueckstadtgraben Y1 - 2013 U6 - https://doi.org/10.1007/s12665-013-2750-z SN - 1866-6280 SN - 1866-6299 VL - 70 IS - 8 SP - 3505 EP - 3522 PB - Springer CY - New York ER -