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- Adrian Höfken
Adrian Höfken |
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Phone: |
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Fax: |
+49 421 218-65311 |
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Email: |
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Room: |
GEO 1, GEO 4120 |
Research Interests
- Marine Geology
- Environmental Magnetism
- Paleomagnetism
- Sediment Geochemistry
PhD Project
The Project focuses on magnetic mineral alteration induced by diffusive and advective oxygen and cation fluxes in ridge flank sediments and the resultant geochemical processes. A special target of this investigation are thin sediment covers on relatively young, porous basaltic crust with active hydrothermal circulation. Most if not all bottom sediments in the deep ocean underwent such conditions during the early stages of sedimentation. The geochemical processes that can be explored in ridge flank sediments therefore offer unique insights into the marine sediment-rock interface itself and is of global relevance.
Beside the normal, downward oxygen diffusion at the seabed, ridge flank sediments in such settings experience an upward directed diffusive (and also localized advective) exchange of oxygen and other elements from the underlying crust. As a consequence the sediment undergoes a double change of redox conditions from deposition under oxic conditions to successively reducing conditions during burial back to oxic conditions induced by upward diffusion from the sediment-rock interface.
This project investigates sediment cores from the Clarion-Clipperton zone (CCZ) in the eastern Pacific. Due to the specific geologic setting and the difficulties of sampling thin sediment covers of not more than few tens of meters thickness, sedimentary records with documented depth-dependent oxygen concentrations are rare and up to date magnetic mineral alteration under such conditions has not yet been studied.
To explicitly investigate the affected redox sensitive iron minerals, a wide range of rock and sediment magnetic methods and instruments are used. These methods comprise frequency dependent susceptibility measurements, measurements with a cryogenic magnetometer such as natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM), hysteresis and first order reversal curve measurements (FORC) and thermomagnetic measurements. The study is substituted by systematic electron microscopic analysis of magnetic mineral extracts as well as laboratory dissolution experiments and geochemical modelling.
CV
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04/2015 - present |
PhD Project in the research group Marine Geophysics, Marum/University of Bremen, Germany PhD Topic: (Non)-Steady Diagenetic Processes in Ridge Flank sediments with Reversing Vertical Redox Zonation |
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10/2015 - 09/2018 |
Master of Science in Marine Geosciences at the University of Bremen Master Thesis: Petromagnetic Characterization of Sediment Source Areas in the Gulf of St. Lawrence / Grand Banks and its application in Provenance Analysis of Laurentian Fan Sediments |
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01/2016 - 08/2016 |
Semester abroad, Master Marine Geosciences, at the University of Bergen and UNIS Svalbard (Norway) |
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10/2012 - 09/2015 |
Bachelor of Science in Geosciences at the University of Bremen Bachelor Thesis: Rock Magnetic and Geochemical Zonation of Western Black Sea Sediments during the last Deglaciation: Terrigenous Influx versus Early Diagenesis |
Research Cruises
| 13.04.2019 - 31.05.2019 | RV Polarstern Cruise PS119, Scotia Sea, South Atlantic Ocean, Marum / University of Bremen, Marum Expeditions / PS119 |
| 30.06.2018 - 24.08.2018 | RV Sonne Cruise SO264, SONNE-EMPEROR, North Pacific Ocean, Geomar Kiel / Alfred Wegener Institute Bremerhaven, Cruise Report SO264 |