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  • 1
    Publication Date: 2021-07-12
    Description: Volcanic eruptionsand earthquakes in the Christiana-Santorini-Kolumbo rift have repeatedly triggered devastating tsunamis including the 1600 BC Late Bronze Age eruption of Santorini, the 1650 eruption of Kolumbo and the 1956 Amorgos earthquake. The Late Bronze Age eruptiontsunami affected large areas of the eastern Mediterranean and contributed to the demise of the Minoan culture on Crete, while the effects of the 1650 Kolumbo and the 1956 Amorgos tsunamis were limited to the islands around the Christiana-Santorini-Kolumborift. Although intensively studied in recent decades, the potential tsunami source parameters of these events remain poorly constrained. The THESEUS project aims to parameterize various potential source parameters associated with these tsunami events using marine high-resolution reflection seismics. For this purpose, we conducted high-resolution 2D and 3D reflection seismic surveys as well as ocean-bottom seismometer refraction seismic experiments covering the Christiana-Santorini-Kolumbo rift during expedition POS538 onboard RV Poseidon in October 2019. Here, we present the first results of the ongoing analysis of our P-Cable 3D seismic dataset, which covers most of the Kolumbo volcanic edifice and a prominent fault zone to the north. In addition, we present 2D seismic profiles covering the Santorini Caldera and pyroclastic flow deposits associated with the Late Bronze Age eruption
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 2
    Publication Date: 2024-02-23
    Description: The past ∼200 million years of Earth's geomagnetic field behavior have been recorded within oceanic basalts, many of which are only accessible via scientific ocean drilling. Obtaining the best possible paleomagnetic measurements from such valuable samples requires an a priori understanding of their magnetic mineralogies when choosing the most appropriate protocol for stepwise demagnetization experiments (either alternating field or thermal). Here, we present a quick, and non‐destructive method that utilizes the amplitude‐dependence of magnetic susceptibility to screen submarine basalts prior to choosing a demagnetization protocol, whenever conducting a pilot study or other detailed rock‐magnetic characterization is not possible. We demonstrate this method using samples acquired during International Ocean Discovery Program Expedition 391. Our approach is rooted in the observation that amplitude‐dependent magnetic susceptibility is observed in basalt samples whose dominant magnetic carrier is multidomain titanomagnetite (∼TM 60–65 , (Ti 0.60–0.65 Fe 0.35–0.40 )Fe 2 O 4 ). Samples with low Ti contents within titanomagnetite or samples that have experienced a high degree of oxidative weathering do not display appreciable amplitude dependence. Due to their low Curie temperatures, basalts that possess amplitude‐dependence should ideally be demagnetized either using alternating fields or via finely‐spaced thermal demagnetization heating steps below 300°C. Our screening method can enhance the success rate of paleomagnetic studies of oceanic basalt samples. Plain Language Summary Oceanic basalts are ideal recorders of the Earth's magnetic field. To decipher magnetic histories recorded in rocks, paleomagnetists need to isolate the magnetization directions and intensities within rocks by one of two possible methods. One method typically involves progressively heating the samples to high temperatures. The other method involves exposing samples to alternating magnetic fields with increasing peak field intensities. Both of these methods are ultimately destructive to the original magnetization preserved within rocks. However, without knowledge of a given rock's magnetic mineralogy, randomly choosing thermal or alternating field demagnetization methods may result in high failure rates. We developed a pre‐screening method to help decide which cleaning method will likely be more successful for a given sample based on low‐field magnetic susceptibility measurements. These measurements do not affect the original magnetic information recorded in a rock, thereby permitting subsequent paleomagnetic studies on the same sample. Our technique can be performed as rapidly as 2 min per sample, is non‐destructive, and does not require complicated sample preparation. Key Points Paleomagnetic studies utilize either alternating field or thermal demagnetization, but it is difficult to choose the best protocol a priori Amplitude‐dependence of magnetic susceptibility measurements permits preliminary magnetic mineralogy characterization in submarine basalts Rapid amplitude‐dependence measurements may aid in deciding upon the best demagnetization protocol for submarine basalt samples
    Type: Article , PeerReviewed
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