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

Abstract

Global climate and oceanic water masses have undergone profound changes during the middle Pleistocene transition; however, due to a lack of foraminiferal fossils, the nonfossiliferous pelagic deposits were less detected in previous reports. In this work, a gravity core from the Kamehameha Basin in the Central Pacific was studied in terms of magnetostratigraphy, clay mineral and geochemical elements. The main results are: (1) nine magnetozones are recognized in the core, which can be correlated to the geomagnetic polarity timescale from chrons C2n to C1n; (2) smectite is the dominant clay mineral, and the others are illite, chlorite and kaolinite; and (3) the sediments are mainly composed of Al2O3, Fe2O3, MnO, Na2O and TiO2. Based on these results, a geochronological framework for the study area was established, and the depositional rates are estimated as 3–7 m/Myr in the Quaternary, showing an increase during the middle Pleistocene transition. By comparing the findings to various paleoenvironmental processes, it is inferred that the increased sedimentation in the Kamehameha Basin may have resulted from the induced weathering processes and the strengthened aeolian inputs from inner Asia. Moreover, regional circulation related to bottom water evolution has experienced a rapid reorganization across the middle Pleistocene transition. All these findings illustrate the potential of deep-sea sediments in the central tropical Pacific in revealing some key features in paleoclimatology and paleoceanography, which are worthy of further investigation in the future.

The Influence of Seamounts on the Enrichment of Rare Earth Elements in Sediments—A Case Study of the Marcus-Wake Seamounts in the Western Pacific Ocean

“…The REY content of the sediments is mainly related to the quantity of fish teeth [6,8,[62][63][64] and micronodules [11,59,60], which are intermediate carriers of REY in the early stage of sedimentation, and the REY will migrate from the micronodules to the fish teeth during diagenesis. Asian dust (black dotted line) after [53][54][55][56][57][58]; Marcus-Wake Seamounts sediment (light blue, green, yellow and red lines) after [6,16,17]; micronodules (blue line), bioapatite fossils (purple line) and philipsites (brown line) after [6]; basalt (pink line) after [65]; bottom water (light blue dotted line) after [36], and volcanic debris (red dotted line) after [66]. [44] REY pattern of all the samples in this study and some references.…”

“…Bi et al also found that the REY content of sediments from core C on the southeastern side of the Niulang Guyot is significantly higher than that from core B on the other side (Figure 6b), and that there is a REY-rich layer with a REY content of more than 2000 ppm in the lower part of core C [6]. Asian dust (black dotted line) after [53][54][55][56][57][58]; Marcus-Wake Seamounts sediment (light blue, green, yellow and red lines) after [6,16,17]; micronodules (blue line), bioapatite fossils (purple line) and philipsites (brown line) after [6]; basalt (pink line) after [65]; bottom water (light blue dotted line) after [36], and volcanic debris (red dotted line) after [66]. [53][54][55][56][57][58]; highly REY-rich mud (red solid circle) after [6,16,17]; basalt (pink square) after [65]; micronodules (blue diamond), bioapatite fossils (red cross) and philipsites (orange triangle) after [6], and volcanic debris (orange pentagram) after [66].…”

“…Asian dust (black dotted line) after [53][54][55][56][57][58]; Marcus-Wake Seamounts sediment (light blue, green, yellow and red lines) after [6,16,17]; micronodules (blue line), bioapatite fossils (purple line) and philipsites (brown line) after [6]; basalt (pink line) after [65]; bottom water (light blue dotted line) after [36], and volcanic debris (red dotted line) after [66]. [53][54][55][56][57][58]; highly REY-rich mud (red solid circle) after [6,16,17]; basalt (pink square) after [65]; micronodules (blue diamond), bioapatite fossils (red cross) and philipsites (orange triangle) after [6], and volcanic debris (orange pentagram) after [66]. [53][54][55][56][57][58]; highly REY-rich mud (red solid circle) after [6,16,17]; basalt (pink square) after [65]; micronodules (blue diamond), bioapatite fossils (red cross) and philipsites (orange triangle) after [6], and volcanic debris (orange pentagram) after [66].…”

“…[53][54][55][56][57][58]; highly REY-rich mud (red solid circle) after [6,16,17]; basalt (pink square) after [65]; micronodules (blue diamond), bioapatite fossils (red cross) and philipsites (orange triangle) after [6], and volcanic debris (orange pentagram) after [66]. [53][54][55][56][57][58]; highly REY-rich mud (red solid circle) after [6,16,17]; basalt (pink square) after [65]; micronodules (blue diamond), bioapatite fossils (red cross) and philipsites (orange triangle) after [6], and volcanic debris (orange pentagram) after [66].…”

“…PAAS-normalized[44] REY pattern of all the samples in this study and some references. Asian dust (black dotted line) after[53][54][55][56][57][58]; Marcus-Wake Seamounts sediment (light blue, green, yellow and red lines) after[6,16,17]; micronodules (blue line), bioapatite fossils (purple line) and philipsites (brown line) after[6]; basalt (pink line) after[65]; bottom water (light blue dotted line) after[36], and volcanic debris (red dotted line) after[66].…”