Abstract. Results of a paleomagnetic, rock magnetic, geochemical, and petrographic study on Jurassic and Cretaceous carbonates in the Vocontian trough support a hypothesized connection between burial diagenetic alteration of smectite and the widespread occurrence of a chemical remanent magnetization (CRM) carried by magnetite. Where smectite has altered to other clay minerals, limestones are characterized by a prefolding, secondary, normal polarity magnetization throughout the basin. The magnetization is interpreted to be a CRM based on low burial depths which cannot cause thermoviscous resetting. Where significant smectite is still present, the CRM is absent/weakly developed, and where the clays show no evidence for burial alteration, the units are characterized by a primary magnetization. CRM intensity also varies with the amount of smectite and burial. Isothermal, anhysteretic, and natural remanent magnetization intensifies increase where smectite has altered, both stratigraphically and geographically. This is interpreted to indicate magnetite authigenesis associated with clay aliagenesis. Superparamagnetic magnetite is more dominant in highly altered units based on the results of low-temperature experiments. All sections away from the Alps have 87 Sr/86Sr values that are similar to coeval seawater, and stable isotopes of carbon and oxygen show no sign of alteration. Omgenic-type fluids therefore are not a likely agent of remagnetization. Near the Alps the rocks are characterized by an additional reversed polarity component which is interpreted to reflect acquisition of the CRM through a reversal. A postfolding magnetization is also present there and strontium isotopic ratios are higher than elsewhere in the basin and might indicate some alteration by orogenic-type fluids. We conclude that burial diagenesis of smectite is the likely cause for the development of the widespread CRM in the Vocontian trough and that this mechanism might explain widespread chemical remagnetization elsewhere.

I would like to thank my advisor. Dr. R. Douglas Elmore for his support. He has been of great help during the past years and he has been instrumental in assisting me to leam how to speak, read, and write the second time around. I wish to thank all of my committee members, Drs. Tom Dewers, Mike Engel, Roger Young, and Richard Henry for feedback and for reviewing the manuscript. Dr. Mike Engel is also acknowledged for his collaboration on the geochemical aspects of the dissertation. I especially thank my "better half (more like 60%), Monika Cogoini, for so many things that I would need a separate chapter in this dissertation to mention them all. She is the best friend, colleague, reviewer, orient express, critic, and moral supporter one can imagine, among all the other things. A tremendous "merci beaucoup" goes to Dr. Serge Ferry from the University of Lyon, France, for his great support in the field and for inspiring conversations. I also want to thank the people at the Institute for Rock Magnetism, Minnesota, especially Dr. Mike Jackson, for help and advice during my visit. I thank Dr. James Lee Wilson for being a great inspiration and Dr. Sue Halgedahl for her help during my visit to her Micromag at the University of Utah. Thanks to Dr. Sanjay Banetjee for being a great colleague and for all the inspiring conversations. I am grateful to Jamie Egger for the many hours she dedicated to my samples in the lab. I am also grateful to all my colleagues in the lab, in the School of Geology and Geophysics, and to all the new friends that I made in Oklahoma who made my stay here enjoyable. Last but not least, I thank my parents for making all this possible.

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Palaeomagnetic and rock magnetic studies on the Kimmeridgian-Portlandian Asphaltkalk deposits of the Hils Syncline near Holzen in northern Germany suggest a connection between bitumen impregnation and magnetization in the limestones. A stable remanent magnetization is only found in the Asphaltkalk deposits, not in non-bitumen-impregnated limestones of the same age. The stable remanence was acquired after folding in this region, as revealed by a palaeomagnetic fold test. The timing of remanence acquisition is Late Cretaceous-early Tertiary, as derived from a comparison of the mean pole of the magnetic component with the European apparent polar wander path (APWP).The decay pattern of the natural remanent magnetization (NRM) during alternating field (AF) and thermal demagnetizaton indicates that the magnetization is carried by magnetite. Isothermal remanent magnetization (IRM) acquisition and thermal decay measurements, as well as hysteresis parameters, are consistent with this interpretation. This study suggests that the creation of authigenic magnetite during the lower Tertiary in the Asphaltkalk deposits might coincide with the timing of hydrocarbon migration into the unit.