5:15 PM - 7:15 PM
[SCG55-P18] Reidentification of the magnetic anomaly lineations in the West Philippine Basin
Keywords:Magnetic anomaly lineations, The West Philippine Basin (WPB), Back-arc spreading, The Philippine Sea Plate (PSP), The Pacific Plate
The West Philippine Basin (WPB) formed by back-arc spreading originated by the subduction of the Pacific Plate 51 Ma (Ishizuka et at., 2024). The Philippine Sea Plate (PSP) was near the equator at the beginning of the subduction of the Pacific Plate. The PSP moved northward while rotating at then (e.g., Wu et al., 2016). Hilde and Lee (1984) identified magnetic anomaly liniations in the WPB. The age of the oldest magnetic anomaly liniations identified by Hilde and Lee (1984) is older than that of beginning of the subduction of the Pacific Plate, implying that the back-arc spreading of the WPB was not initialed by the plate subduction, and is not sufficient to explain the formation process of the basin. Although several studies have partially modified this identification (e.g., Deschamps and Lallemand, 2002; Sasaki et al., 2014), no reexamination of magnetic anomaly lineations in the entire basin has been accomplished. Several studies reported that there are topographic features in the basin that contradict the identification magnetic anomaly liniations by the identification Hilde and Lee (1984) (e.g., Deschamps and Lallemand, 2002; Taylor and Goodliffe, 2004; Luo et al., 2024). To address this situation, we reidentify magnetic anomaly lineations in the WPB.
We made a grid file of magnetic anomaly of the entire WPB for identification of magnetic anomaly lineations. Crossover errors were reduced by the method of Ishihara (2015). Crossover errors that could not be reduced by this method were reduced by subtracting the residual between the target data and the grid file without the target data. We used the geomagnetic polarity timescale by Ogg (2020) for our study.
Our identification showed that the oldest magnetic anomaly lineation is 20r (~50 Ma). This result supports the theory that the WPB began to open due to the Pacific Plate starting to subduct under the Philippine Sea Plate ~51 Ma (Ishizuka et al., 2024). The distribution of magnetic anomaly liniations in the WPB indicates that the last spreading part is the eastern part of the CBF, which partially supports the basin spreading process proposed by Luo et al. (2024).
We made a grid file of magnetic anomaly of the entire WPB for identification of magnetic anomaly lineations. Crossover errors were reduced by the method of Ishihara (2015). Crossover errors that could not be reduced by this method were reduced by subtracting the residual between the target data and the grid file without the target data. We used the geomagnetic polarity timescale by Ogg (2020) for our study.
Our identification showed that the oldest magnetic anomaly lineation is 20r (~50 Ma). This result supports the theory that the WPB began to open due to the Pacific Plate starting to subduct under the Philippine Sea Plate ~51 Ma (Ishizuka et al., 2024). The distribution of magnetic anomaly liniations in the WPB indicates that the last spreading part is the eastern part of the CBF, which partially supports the basin spreading process proposed by Luo et al. (2024).