Paleomagnetism, Rock Magnetism, Baked Contact Test, Anisotropy of Magnetic Susceptibility
The mafic intrusion of Nodule Point, Marrowstone Island, WA has sparse scientific literature to substantiate the local geologic history around its emplacement conditions. To fill this gap, rock magnetism and paleomagnetic methods have been applied to the intrusion and the sandstone of Scow Bay host rock. Samples taken from both lithologies were subject to thermal and alternating field demagnetization to assess paleomagnetic components. The Anisotropy of Magnetic Susceptibility (AMS) of samples was measured, and the maximum axis of susceptibility, K1, was used as an analog to hypothesize emplacement conditions. The host rock: the sandstone of Scow Bay, returned magnetization characteristics of a passed Baked Contact Test, however, the Unbaked Zone was not observed, deeming the test tentative. Bulk susceptibility of the sandstone was found to be anonymously decrease with increasing distance, suggesting possible chemical alterations to ferromagnetic and paramagnetic carriers. Average magnetization directions for both the basalt and sandstone sample sites returned values similar to an Eocene reference paleomagnetic direction, however, a number of factors reduce the reliability of this assessment.
Nuncio, Charlie, "Magnetic Methods to Characterize the Emplacement of the Nodule Point Intrusion (Marrowstone Island, WA)" (2022). Geology Graduate and Undergraduate Student Scholarship. 8.
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