Insolation-paced sea level during the Early Pleistocene, Taiwan
- 1Applied Research in Ichnology and Sedimentology (ARISE) Group, Department of Earth Sciences, Simon Fraser University, Burnaby, Canada
- 2Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
- 3LIAG – Leibniz Institute for Applied Geophysics, Geozentrum Hannover, Hannover, Germany
- 4Department of Geosciences, National Taiwan University, Taipei, Taiwan
- 5Departement of Earth Sciences, National Central University, Taoyuan, Taiwan
- 6Departement of Earth Sciences, National Cheng-Kung University, Taïnan, Taiwan
The Pleistocene was a phase of global cooling of the Earth through which glacial-interglacial cycles occurred, and the growth and decay of the ice-sheets resulted in quasi-cyclic sea-level fluctuations driven by orbital forcing. Despite that summer insolation is mostly controlled by precession, the records of the glacial cycles showcase a significant periodicity of ~41 kyrs during the Early Pleistocene forced by Earth’s obliquity (tilt) that varies the latitudinal distribution of insolation especially in high latitudes. The dominance of obliquity over precession in marine archives is commonly attributed to the in-phase effect of obliquity-related insolation versus the opposite-phased influence of precession, which may cancel out the summer insolation signal received by the southern and northern hemispheres.
Here, we present a clastic shallow marine record from the Cholan Formation (Early Pleistocene; Taiwan). Facies analysis indicates that quasi-cyclic deposition occurred in shoreface to offshore environments in the paleo-Taiwan Strait. The magnetobiostratigraphic framework indicates that the studied section occurs in the lower part of the Matuyama subchron (1.925 - 2.595 Ma) close to the lower limit of the Olduvai (1.925 Ma) normal polarity subchron. Comparison of the stratigraphy to a d18O isotope record of benthic foraminifera and orbital curves of precession and obliquity at the time of sediment accumulation reveals a good correlation between depositional cycles and the Northern Hemisphere summer insolation, demonstrating precession dominated sea-level fluctuations during the Early Pleistocene. These results underpin recent findings suggesting that d18O isotope records of benthic foraminifera have a more significant precession signal than previously described. This study also demonstrates that shallow-marine stratigraphic successions in high-accommodation and high-sedimentation basins can be outstanding climate archives, possibly even preserving sediment flux responding to half-precession cycles.
How to cite: Vaucher, R., Dashtgard, S. E., Horng, C.-S., Zeeden, C., Dillinger, A., Pan, Y.-Y., Setiaji, R. A., Chi, W.-R., and Löwemark, L.: Insolation-paced sea level during the Early Pleistocene, Taiwan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1433, https://doi.org/10.5194/egusphere-egu21-1433, 2021.