11:45 AM - 12:00 PM
[SGL22-10] Chronostratigraphy around the Quaternary base of a Plio-Pleistocene succession in the southernmost part of the Boso Peninsula.
The base of the Quaternary System is defined by the Gelasian GSSP (Global boundary Stratotype Section and Point) in the Monte Narbone formation at the Monte San Nicola section, southern Sicily. Since a δ18O stratigraphy has not been constructed, and also the Gauss-Matsuyama geomagnetic reversal boundary (G-M boundary), which is the stratigraphic guide to define the Quaternary base, has not been well documented at the formation, it is needed to construct another standard section to be able to compensate for the choronostratigraphic inadequacies lying on the Quaternary base.
To constructed a δ18O stratigraphy for the GM-1 core drilled through the Quaternary base from the Minamiasai formation, Chikura group, we collected 39 samples from the siltstone part of the GM-1 core at every 1 m stratigraphic interval. We disaggregated the rock samples using sodium sulfate and picked benthic foraminiferal tests. This research used Bolivinita spp. for isotopic measurements and successfully deduced δ18O values from 34 samples. Using three tie points, we developed an age model for the GM-1 core by comparing our δ18O data with the LR04 stack curve(Lisieckci and Rayamo, 2005). As a result, the top and the base of the GM-1 core are dated 2.561Ma and 2.63Ma, corresponding to the Marine isotope stage (MIS) 102 and G1, respectively. According to a magnetostratigraphy of the GM-1 core, a magnetic reversal that expected as the G-M boundary at 10m depth. Our new age model shows that the age of this point is dated 2.588Ma, which corresponds to MIS103.
In the Monte Narbone formation, the G-M boundary was reported as in MIS 104 at 1 m below the Quaternary base, which has been contradicted by observation of it in MIS 103 at a high-resolution deep-sea sediment core(Ohno et al.,2012).Therefore, our new data will contribute to setting the age issue for the G-M boundary and the Quaternary base.
To constructed a δ18O stratigraphy for the GM-1 core drilled through the Quaternary base from the Minamiasai formation, Chikura group, we collected 39 samples from the siltstone part of the GM-1 core at every 1 m stratigraphic interval. We disaggregated the rock samples using sodium sulfate and picked benthic foraminiferal tests. This research used Bolivinita spp. for isotopic measurements and successfully deduced δ18O values from 34 samples. Using three tie points, we developed an age model for the GM-1 core by comparing our δ18O data with the LR04 stack curve(Lisieckci and Rayamo, 2005). As a result, the top and the base of the GM-1 core are dated 2.561Ma and 2.63Ma, corresponding to the Marine isotope stage (MIS) 102 and G1, respectively. According to a magnetostratigraphy of the GM-1 core, a magnetic reversal that expected as the G-M boundary at 10m depth. Our new age model shows that the age of this point is dated 2.588Ma, which corresponds to MIS103.
In the Monte Narbone formation, the G-M boundary was reported as in MIS 104 at 1 m below the Quaternary base, which has been contradicted by observation of it in MIS 103 at a high-resolution deep-sea sediment core(Ohno et al.,2012).Therefore, our new data will contribute to setting the age issue for the G-M boundary and the Quaternary base.