10:45 AM - 11:00 AM
[HQR04-07] Middle Pleistocene terraces in the Chita Peninsula, near Nagoya, central Japan
Keywords:Middle Pleistocene terrace, Pollen analysis, Dating, Chita peninsula, Chibanian
1. Introduction
The Middle Pleistocene terraces in the Chita Peninsula had been subdivided into two surfaces and formations since Matsuda (1969). The authors re-examined topographic features and stratigraphy of them and tried to date them by pollen analysis.
2. Field survey
A large outcrop (Fig. 1) in the central area of the peninsula shows that the highest terrace that named “Taketoyo terrace” is subdivided two terrace surfaces, and its deposits are also subdivided two units by an unconformity. The higher one (newly named “H 1 terrace”) is composed by gravelly deposits and distributed on the top of hills that constitute watershed between the Kinuura on the east of peninsula and the Ise bay on the west of peninsula.. The H 1 terrace deposits contain a lot of rhyolite gravels. The lower one (newly named “H 2 terrace” is composed by sand and mud with bioturbation. The other Middle Pleistocene terrace 1 step lower than H 2 terrace (newly named “H 3 terrace” ) is composed with two marine mud and fluvial top gravels. Rhyolite gravels are common in the H 2 terrace and H 3 terrace deposits in the western coast, however, it is few in them in the eastern coast.
3. Pollen analysis
Results of the pollen analysis in each terrace deposits are shown in Table 1.
4. Dating
All of the H1 ~ H3 terraces are late Middle Pleistocene (Chibanian) interglacial ones, because of red (2.5 ~ 5 YR in the Munsell color index) surface soil, degree of weathering of gravels (intensely weathered to be soft and brittle) and warm temperate pollen assemblages. H I is thought to be dated to a warm climate stage around MIS 11 fluvial terrace, H2 is thought to be MIS 9 marine terrace, H 3 is thought to be MIS marine to river mouth terrace.
The Middle Pleistocene terraces in the Chita Peninsula had been subdivided into two surfaces and formations since Matsuda (1969). The authors re-examined topographic features and stratigraphy of them and tried to date them by pollen analysis.
2. Field survey
A large outcrop (Fig. 1) in the central area of the peninsula shows that the highest terrace that named “Taketoyo terrace” is subdivided two terrace surfaces, and its deposits are also subdivided two units by an unconformity. The higher one (newly named “H 1 terrace”) is composed by gravelly deposits and distributed on the top of hills that constitute watershed between the Kinuura on the east of peninsula and the Ise bay on the west of peninsula.. The H 1 terrace deposits contain a lot of rhyolite gravels. The lower one (newly named “H 2 terrace” is composed by sand and mud with bioturbation. The other Middle Pleistocene terrace 1 step lower than H 2 terrace (newly named “H 3 terrace” ) is composed with two marine mud and fluvial top gravels. Rhyolite gravels are common in the H 2 terrace and H 3 terrace deposits in the western coast, however, it is few in them in the eastern coast.
3. Pollen analysis
Results of the pollen analysis in each terrace deposits are shown in Table 1.
4. Dating
All of the H1 ~ H3 terraces are late Middle Pleistocene (Chibanian) interglacial ones, because of red (2.5 ~ 5 YR in the Munsell color index) surface soil, degree of weathering of gravels (intensely weathered to be soft and brittle) and warm temperate pollen assemblages. H I is thought to be dated to a warm climate stage around MIS 11 fluvial terrace, H2 is thought to be MIS 9 marine terrace, H 3 is thought to be MIS marine to river mouth terrace.