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Research Group Division of GeoEnvironmental Science


Group of Paleoenvironmental Changes and Evolutional Paleontology

•Professor Yasuhumi Iryu,
•Associate Professor Ryuji Asami,
•Associate Professor Noritoshi Suzuki, specializing in Micropaleobiology, and Ocean Plankton
•Assistant Professor Tsutomu Yamada, specializing in Isotope Geochemistry, Carbonate Geochemistry
•Assistant Professor Hideko Takayanagi,
The geosphere, hydrosphere, and biosphere on Earth have interacted and evolved through Earth's history. Our group conducts sedimentological, paleontological, and geochemical studies to reconstruct paleoclimatic and paleoceanographic variations and to elucidate biogeochemical evolution.

Understanding climate change from paleoclimate and paleoceanographic reconstructions

Understanding past global environmental changes on various time scales is important for clarifying the mechanisms of climate change and geologic history on Earth. Nowadays, we can observe real-time environmental conditions (e.g., air and seawater temperature/salinity/pH and CO2 concentration) using satellites and instruments. However, such instrumental records are available only for the last ~100 years. In order to understand the past environmental changes on the Earth in older ages, it is necessary to obtain such information from proxy records in paleoenvironmental archives, such as carbonate sediments and fossils.
Our group is mainly interested in paleoclimatic and paleoceanographic changes in tropical to temperate regions and shallow to intermediate waters. Our study fields range from carbonate mountains/islands to coral reefs of the Indo-Pacific region. We perform sedimentological observation of carbonate deposits and the geochemical analysis (e.g., isotopes and trace elements) of carbonate skeleton/shells (e.g., corals, clams, brachiopods, etc.) and rocks (including stalagmites and dolomites).

[left]From Mud Sea (Shimajiri Gr.) to Coral Sea (Ryukyu Gr.) / [right]Expansion of coral reefs at 0.8 Ma

A survey of coral reefs


Understanding biological evolution from evolutionary paleontology

Biological evolution is essentially the stochastic emergence of a series of genetic changes at a certain period. The 'timing' of evolution is closely related to drastic changes in the global environment. Evolutionary paleontology is a field to study the causes of biological evolution using fossils.
Microfossils can be studied with only a few grams of sediments and occur continuously throughout the core sediments, providing the best insight into evolutionary trend.
Radiolarians are siliceous-shelled plankton with continuous fossil record throughout the Phanerozoic. They are highly diversified and 10,000 species have been found in 500 million years. We analyze the molecular phylogeny of these species and integrate them to delineate their evolution.

Microfossils in sediments