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.
Highlights
The past climate was dominated by a symmetric 41 kyr cycle in the early Pleistocene, and by an asymmetric 100 kyr cycle since the middle Pleistocene [1], and this change in dominant cycles is the so-called Middle Pleistocene transition (MPT, ~1.45–0.9 Ma)
High percentages of smectite in clay minerals usudemonstrates that the sediments are closely related to volcano glasses, while illite and ally demonstrates that the sediments are closely related to volcano glasses, while illite and chlorite are from physical weathering and kaolinite can indicate warm and humid climates, chlorite are from physical weathering and kaolinite can indicate warm and humid cliwhich is strongly controlled by continental hydrolysis [23,24,25,26,27]
Based on magnetostratigraphy of the sediments of core PC15, we established a chronological framework for deep-sea sediments in the Kamehameha Basin in the Quaternary
Summary
The past climate was dominated by a symmetric 41 kyr cycle in the early Pleistocene, and by an asymmetric 100 kyr cycle since the middle Pleistocene [1], and this change in dominant cycles is the so-called Middle Pleistocene transition (MPT, ~1.45–0.9 Ma). The pelagic sediments in the tropical Pacific may have fully recorded changes in paleoceanography, provenance and global climate, and their characteristics can be employed to reveal such information [9]. Sedimentary properties ofproperties the deep-sea sediments in sediments the Kamehameha. Sedimentary of the deep-sea in the Kamemay record themay interactions between various climaticvarious and oceanic systems. Basin record the interactions between climatic and oceanic systems. The Combining results of magnetostratigraphy, and geochemistry, the properties of the deep-sea sediments were well studied the clay minerals and geochemistry, the properties of the deep-sea sediments were wellinstudQuaternary. (2) changes in the mental the proxies the MPT, we attempt study (1) the sedimentary processes,. Changes in the provenance, and (3)evolution bottom water in the study area
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