GP003-05
High-resolution Magnetostratigraphy, Relative Paleointensity (RPI) and Age Model Study of IODP Expedition 381 From the Gulf of Corinth (Greece).
High-resolution Magnetostratigraphy, Relative Paleointensity (RPI) and Age Model Study of IODP Expedition 381 From the Gulf of Corinth (Greece).
Monday, 14 December 2020: 07:12
Virtual
Abstract:
We have studied the magnetostratigraphy, rock magnetism, paleomagnetic properties, and relative paleointensity (RPI) of Plio-Quaternary syn-rift sedimentary sequence recovered during IODP Expedition 381 from the Gulf of Corinth (Greece). A total of 2700 discrete cubic (~8 cm3) specimens were collected throughout the ~1.9 km of drilled sedimentary sequence at ~ 0.75 m spacing from four holes (M0078A, M0078B, M0079A, and M0080A). Bulk magnetic susceptibility (k) and natural remanent magnetization (NRM) were measured before stepwise demagnetizing the samples using 13 alternating field (a.f.) steps up to 100 mT. Characteristic remanent magnetization (ChRM) components were isolated at 25-50 mT after having removed the secondary components of magnetization at 5-15 mT. The NRM intensity is characterized by a direct linear
relationship with the magnetic susceptibility. Curie points (i.e., k-T) indicate the presence of at least four predominant magnetic mineral phases, with temperatures of 320-400°C (greigite), 520 to 575°C (Ti-poor magnetite) and ~600°C (maghemite). The inclination of the ChRM components from the four holes show both positive and negative inclinations with values close to the expected inclination at the sampling locality (i.e., 57°), which allowed us to build a preliminary magnetostratigraphy for the cored sediments. A number of intervals within the youngest syn-rift sediments (lithostratigraphic Unit 1) are characterized by lower or higher inclinations, which might represent excursions of the geomagnetic field documented within the Brunhes and Matuyama Chrons. In order to test this hypothesis, we have imparted anhysteretic remanent magnetizations (ARM) and saturation isothermal remanent magnetizations (SIRM) to all the recovered specimens, and used the ratios between their intensity and the NRM and susceptibility to determine the relative paleointensity (RPI) and
compare it to the geomagnetic instability time scale (GITS) of Singer (2014) and to the PISO-1500 RPI reference curve of Channell et al. (2009) to produce a high-definition age model. Our results match relatively wellwith most of the variations of the geomagnetic field (direction and intensity) from ~1076ka to present.
relationship with the magnetic susceptibility. Curie points (i.e., k-T) indicate the presence of at least four predominant magnetic mineral phases, with temperatures of 320-400°C (greigite), 520 to 575°C (Ti-poor magnetite) and ~600°C (maghemite). The inclination of the ChRM components from the four holes show both positive and negative inclinations with values close to the expected inclination at the sampling locality (i.e., 57°), which allowed us to build a preliminary magnetostratigraphy for the cored sediments. A number of intervals within the youngest syn-rift sediments (lithostratigraphic Unit 1) are characterized by lower or higher inclinations, which might represent excursions of the geomagnetic field documented within the Brunhes and Matuyama Chrons. In order to test this hypothesis, we have imparted anhysteretic remanent magnetizations (ARM) and saturation isothermal remanent magnetizations (SIRM) to all the recovered specimens, and used the ratios between their intensity and the NRM and susceptibility to determine the relative paleointensity (RPI) and
compare it to the geomagnetic instability time scale (GITS) of Singer (2014) and to the PISO-1500 RPI reference curve of Channell et al. (2009) to produce a high-definition age model. Our results match relatively wellwith most of the variations of the geomagnetic field (direction and intensity) from ~1076ka to present.