Paleomagnetism of Igenous Rocks from Shatsky Rise
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Shatsky Rise is oceanic plateau in the northwest part of the Pacific Ocean, and the formation of Shatsky Rise is poorly known. To get a better understanding of the formation Integrated Ocean Drilling Program (IODP) Expedition 324 drilled five sites: Sites U1347 and U1348 on Tamu Massif, Site U1349 and U1350 on Ori Massif, and Site U1346. Paleomagnetic measurements of the basaltic flows recovered can give insight into the timing and paleolatitude of each site. Relating the change in principle component inclination over depth at each site to the paleosecular variation of the geomagnetic field can better constrain the timing of the eruptions. Measurements were carried out by different sources during IODP Expedition 324 and after. This study is an amalgamation of the results from Sites U1346, U1347, U1349, and U1350. Samples from each site were divided into half and demagnetized using alternating field (AF) demagnetization and thermal (TH) demagnetization. After the drilling overprint was removed most samples displayed univectorial decay in the orthogonal vector plot. AF demagnetized samples displayed a low median destructive field (MDF) behavior, <10 mT, and a moderate MDF behavior, >10-20 mT. Thermal demagnetized samples displayed three behaviors: a rapid decline in magnetic intensity after moderate temperature steps behavior, a linear decline in magnetic intensity behavior, and some samples displayed a small segment of self-reversal at 300°-350°. Using the Cox and Gordon (1984) method Sites U1346, U1347, and U1349 displayed very little variation in principal component inclinations over depth, implying a relatively rapid lava emplacement of 10^2-10^3 years. Site U1350 display more variation, implying a longer eruptive time frame of 10^4-10^5years. With the assumption of a normal polarity the paleolatitude estimates are -11.0° +22.2°/-21.4° for Site U1346, 11.3° 27.4°/-28.5° for Site U1347, -5.0° +20.8°/-20.6° for Site U1349 and 1.6° ±7.7 ° for Site U1350. The site paleolatitudes imply that Ori Massif (Sites U1350 and U1349) formed at the equator and Tamu Massif (Site U1347) and Shirshov Massif (Site U1346) formed slightly north and south of the equator respectively. All results are consistent with the interpretation that Shatsky Rise formed near the equator.
Pueringer, Margaret (2013). Paleomagnetism of Igenous Rocks from Shatsky Rise. Master's thesis, Texas A&M University. Available electronically from