Interrelations of tectonic deformation and surface erosion with West Antarctic Ice Sheet dynamics
Final Report Abstract
In summary, the goals of this project were reached in the following way: (i) Crustal properties: characterization of basement rocks from the Amundsen Sea Embayment We investigated the crustal basement underlying the Marie Byrd Seamounts in the offshore realm and found that their thermotectonic history differs significantly from the basement rocks exposed onshore Marie Byrd Land, in that they record two post-Cretaceous age groups, which we interpret as reflecting magmatic activity during the late Oligocene and late Miocene. (ii) Constraining Cretaceous to present tectonic evolution of West Antarctica The investigated samples turned out to partly also record the pre-Cretaceous evolution, indicating a km-thick back-arc basin associated with Proto-Pacific subduction beneath Gondwana during the Jurassic to early Cretaceous. Our data also show that practically the whole Pacific margin of Gondwana experienced tectonic activity and rapid exhumation during the Cretaceous, although, particularly during the late Cretaceous, related to different tectonic regimes. For the Marie Byrd Land and Thurston Island Blocks of West Antarctica, the Cenozoic was mostly characterized by tectonic quiescence, with only localized activity related to extension of the West Antarctic Rift System. By contrast, the area around the Scotia Sea experienced differential exhumation and small-scale variations during the Cenozoic, including Oligocene and late Miocene magmatic activity, and localized rapid exhumation during the Pliocene. (iii) Reconstructing the denudation history with inferences on the paleo-topographic evolution Our data indicate little Cenozoic tectonic activity for western Marie Byrd Land and Thurston Island, implying low-lying, subdued topography and limited emergent areas that would have allowed supporting continental ice sheets already during the Eocene or early Oligocene. (iv) Measuring the geothermal heat flow, its distribution and variations Geothermal heat flow was directly measured and estimated on the basis of Curie depths inversions. Generally, heat flow values show strong spatial variations, with highest values along the boundary of the Thurston Island and Marie Byrd Land continental blocks, offshore the Thwaites Glacier. Average heat flow values range between ~65 to 95 mW/m2, and locally increase to >100 mW/m2.
Publications
- (2017). Geothermal heat flux in the Amundsen Sea sector of West Antarctica: New insights from temperature measurements, depth to the bottom of the magnetic source estimation and thermal modelling. Geochemistry Geophysics Geosystems, 18, 2657-2672
Dziadek, R., Gohl, K., Diehl, A., Kaul, N.
(See online at https://doi.org/10.1002/2016GC006755) - (2019). Elevated geothermal surface heat flow in the Amundsen Sea Embayment, West Antarctica. Earth and Planetary Science Letters, 506, 530-539
Dziadek, R., Gohl, K., Kaul, N., and Science Team of Expedition PS104
(See online at https://doi.org/10.1016/j.epsl.2018.11.003) - 2019. Thurston Island (West Antarctica) between Gondwana subduction and continental separation: a multi-stage evolution revealed by apatite thermochronology. Tectonics 38, 879-897
Zundel, M., Spiegel, C., Mehling, A., Lisker, F., Hillenbrand, C-D., Monien, P., Klügel, A.
(See online at https://doi.org/10.1029/2018TC005150)
