Pleistocene magnetostratigraphy of four cores in the West Philippian Basin and regional sedimentary shift during the Mid‐Pleistocene transition

Abstract

The Philippine Sea is a well-preserved, extinct, marginal basin, and due to generally deeper than the carbonate compensation depth, the geochronology and its geological significance of the abyssal sediments are less studied in previous researches. In this work, we studied the magnetostratigraphy of four gravity cores from the centre of the West Philippian Basin and establish a reliable chronology for sedimentary sequences in the Pleistocene. The main results include: (a) several magnetozones are recognized in the studied four cores, which can be correlated to the geomagnetic polarity timescale from chrons C1n to C2An (0-3.0 Ma); (b) since~1.2 Ma, the depositional rates across the West Pacific are relatively consistent, about 160-250 cm/ Myr; (c) a transition in depositional rates around~1.2 Ma was identified in the studied area, from a spatial variety in the Early Pleistocene to a persistent pattern since the Middle Pleistocene. Based on these findings, we report that this sedimentary shift in the Philippian Sea can be correlated to global climate changes during the Mid-Pleistocene transition, representing a major change in the studied area. Therefore, we suggest that the sedimentary processes in the studied area can be linked to a common shift in palaeoclimatology across the inner Asian continent, the Philippian Sea, and the tropical Pacific during the late Early Pleistocene.

Magnetostratigraphy of Abyssal Deposits in the Central Philippine Sea and Regional Sedimentary Dynamics During the Quaternary

“…More specifically, the similarity of the SARs in the upper parts of the cores from the Western Pacific (200–300 cm/Myr) suggests a relatively consistent depositional process in the Middle Pleistocene, which has been mentioned in Yao et al. (2021); however, in the lower parts of the cores, the SARs vary greatly, from 50 to 400 cm/Myr, indicating a substantial spatial variability of sedimentary processes in the Early Pleistocene. This consistency of the SARs between cores in the past 0.8 Ma offers an opportunity to visualize the spatial pattern by plotting the thickness and SAR of each core, though only 16 cores used in this study.…”

“…The most striking phenomenon revealed by the magnetostratigraphic framework in the Central Philippine Sea is the change in SAR during ∼1.5–1.0 Ma (Figure 6), and it likely represents a major transition in the evolution of the abyssal environmental. As suggested in previous studies (Yao et al., 2021; Yi et al., 2020), three factors are likely responsible for this transition: sediment flux, oceanographic setting, and topographic background.…”

“…As a fundamental topic in sedimentary research, the geochronology and sedimentary dynamics of abyssal deposits are poorly documented compared with tectonic activity, magma and sedimentary mineralogy. For example, an increase in the sediment accumulation rate (SAR) was identified in the late Early Pleistocene in the Philippine Sea and the surrounding areas based on magnetostratigraphy (Deng et al., 2016; Yao et al., 2021; Yi et al., 2020), while a decrease in SAR was observed at a site in the Central Philippine Sea (Hu et al., 2021). Moreover, clay minerals in the Philippine Sea can be used to identify sediment sources (F. Jiang et al., 2013), the spatial differences of which may be controlled by seafloor topography and aeolian inputs (Huang et al., 2017).…”

Geochemical and Mineral Properties of Quaternary Deep-Sea Sediments in the Central-Tropical Pacific and Its Response to the Mid-Pleistocene Transition

“…Within the MPT, SARs of core PC15 and ODP Site 842 [13] significantly increased, from 3 m/Ma to 6.38 m/Ma in core PC15, and from 4.76 m/Ma to 10.63 m/Ma at ODP Site 842 [13]. This increase in SARs is not only evident in the Kamehameha Basin, but also in the southern slope of Mariana Trench [14], the Western Pacific and the Philippian Sea [31,32] (Figure 8). [6] indicates global climate changes from 41 kyr to 100 kyr world.…”

“…Site 842 [13]. This increase in SARs is not only evident in the Kamehameha Basin, but also in the southern slope of Mariana Trench [14], the Western Pacific and the Philippian Sea [31,32] (Figure 8).…”