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MIS11–19 pollen stratigraphy from the 250‐m Choshi core, northeast Boso Peninsula, central Japan: Implications for the early/mid‐Brunhes (400–780 ka) climate signals
Author(s) -
Okuda Masaaki,
Nakazato Hiroomi,
Miyoshi Norio,
Nakagawa Takeshi,
Okazaki Hiroko,
Saito Saneatsu,
Taira Asahiko
Publication year - 2006
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/j.1440-1738.2006.00533.x
Subject(s) - geology , tephra , pollen , paleontology , palynology , interglacial , glacial period , stratigraphy , tephrochronology , paleogene , physical geography , volcano , geography , botany , cretaceous , tectonics , biology
The 250‐m Choshi core (CHOSHI‐1), drilled from hemipelagic muds of the Inubo Group, has been physically, geochemically and tephrochronologically analyzed back to 1 Ma. We provide pollen results for the 19–169 m section of the core (400–780 ka) bracketed by the marker tephra Ty1 (equivalent to J4) and the Brunhes–Matuyama paleomagnetic boundary. The results show good agreement with the corresponding oxygen isotope (δ 18 O) profile, with high δ 18 O intervals dominated by boreal conifers Picea , Abies , Pinus (subgen. Haploxylon ) and Tsuga ( diversifolia ), whereas low δ 18 O intervals are dominated by temperate conifers Cryptomeria , Taxaceae‐Cephalotaxaceae‐Cupressaceae and Sciadopitys . In order to confirm pollen‐climate relations for the relevant taxa, a modern surface pollen dataset for the Japanese archipelago was consulted. In this analysis, the ratios of Cryptomeria / Picea and temperate/boreal conifers serve as proxies for the 100‐kyr glacial/interglacial cycle during the Middle Pleistocene. Distinct signals for marine isotope stages (MIS) 11, 12, 13–15, 16, 17 and 18–19 are recognized in accordance with the tephrochronology and δ 18 O of the same core. Application of the criteria to an independent pollen record from Lake Biwa provides an integrated pollen stratigraphy for mid‐latitude Japan during the past 800 ky. Some degree of uncertainty remains in the chronology of the MIS13–15 interval, relating to the uncertainty in the eruption age of widespread tephra Ks11.