@article{HeckenbachBruneGlerumetal.2021, author = {Heckenbach, Esther Lina and Brune, Sascha and Glerum, Anne C. and Bott, Judith}, title = {Is there a speed limit for the thermal steady-state assumption in continental rifts?}, series = {Geochemistry, geophysics, geosystems : G 3 ; an electronic journal of the earth sciences}, volume = {22}, journal = {Geochemistry, geophysics, geosystems : G 3 ; an electronic journal of the earth sciences}, number = {3}, publisher = {Wiley}, address = {Hoboken, NJ}, issn = {1525-2027}, doi = {10.1029/2020GC009577}, pages = {18}, year = {2021}, abstract = {The lithosphere is often assumed to reside in a thermal steady-state when quantitatively describing the temperature distribution in continental interiors and sedimentary basins, but also at active plate boundaries. Here, we investigate the applicability limit of this assumption at slowly deforming continental rifts. To this aim, we assess the tectonic thermal imprint in numerical experiments that cover a range of realistic rift configurations. For each model scenario, the deviation from thermal equilibrium is evaluated. This is done by comparing the transient temperature field of every model to a corresponding steady-state model with an identical structural configuration. We find that the validity of the thermal steady-state assumption strongly depends on rift type, divergence velocity, sampling location, and depth within the rift. Maximum differences between transient and steady-state models occur in narrow rifts, at the rift sides, and if the extension rate exceeds 0.5-2 mm/a. Wide rifts, however, reside close to thermal steady-state even for high extension velocities. The transient imprint of rifting appears to be overall negligible for shallow isotherms with a temperature less than 100 degrees C. Contrarily, a steady-state treatment of deep crustal isotherms leads to an underestimation of crustal temperatures, especially for narrow rift settings. Thus, not only relatively fast rifts like the Gulf of Corinth, Red Sea, and Main Ethiopian Rift, but even slow rifts like the Kenya Rift, Rhine Graben, and Rio Grande Rift must be expected to feature a pronounced transient component in the temperature field and to therefore violate the thermal steady-state assumption for deeper crustal isotherms.}, language = {en} } @article{MorgensternOverduinGuentheretal.2020, author = {Morgenstern, Anne and Overduin, Pier Paul and G{\"u}nther, Frank and Stettner, Samuel and Ramage, Justine and Schirrmeister, Lutz and Grigoriev, Mikhail N. and Grosse, Guido}, title = {Thermo-erosional valleys in Siberian ice-rich permafrost}, series = {Permafrost and Periglacial Processes}, volume = {32}, journal = {Permafrost and Periglacial Processes}, number = {1}, publisher = {Wiley}, address = {Hoboken}, issn = {1045-6740}, doi = {10.1002/ppp.2087}, pages = {59 -- 75}, year = {2020}, abstract = {Thermal erosion is a major mechanism of permafrost degradation, resulting in characteristic landforms. We inventory thermo-erosional valleys in ice-rich coastal lowlands adjacent to the Siberian Laptev Sea based on remote sensing, Geographic Information System (GIS), and field investigations for a first regional assessment of their spatial distribution and characteristics. Three study areas with similar geological (Yedoma Ice Complex) but diverse geomorphological conditions vary in valley areal extent, incision depth, and branching geometry. The most extensive valley networks are incised deeply (up to 35 m) into the broad inclined lowland around Mamontov Klyk. The flat, low-lying plain forming the Buor Khaya Peninsula is more degraded by thermokarst and characterized by long valleys of lower depth with short tributaries. Small, isolated Yedoma Ice Complex remnants in the Lena River Delta predominantly exhibit shorter but deep valleys. Based on these hydrographical network and topography assessments, we discuss geomorphological and hydrological connections to erosion processes. Relative catchment size along with regional slope interact with other Holocene relief-forming processes such as thermokarst and neotectonics. Our findings suggest that thermo-erosional valleys are prominent, hitherto overlooked permafrost degradation landforms that add to impacts on biogeochemical cycling, sediment transport, and hydrology in the degrading Siberian Yedoma Ice Complex.}, language = {en} }