Marine Ecosystems Research Department - jamstec japan agency ...

JAMSTEC 2002 Annual Report
Institute for Frontier Research on Earth Evolution (IFREE)
analyses, and rock experiments. A result using this
code on the ES indicates that segmentation of the
source region is caused by a complex slab geometry.
Furthermore, optimization on the ES of the crustal
activity simulation code for transcurrent plate boundaries
and the development of the poro-viscoelastic
FEM code for investigation of fluid around fault zones
were also promoted (Fig.).
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Research Program for Paleoenvironment
1. Research Overview
The ultimate goal of our group's research is the
establishment of a new view on the link between the
Earth and the biosphere over the history of the Earth.
We are focusing on the last million years when
the geological record is preserved in deep sea sediments.
Currently, our research focuses on the following
three specific fields:
a) Climatic change in the Cretaceous Greenhouse
and Late Cenozoic Icehouse Earth
b) Sedimentation and degradation processes of
organic matter on the continental margin
c) Database for paleoclimatology and paleogeography
of continents and oceans
Here, we briefly summarize the results of each topic
to present an overview of the progress of our research
in FY.
2. Cretaceous Greenhouse Earth
2.1. Investigation of Cretaceous black shales
It has been known that several organic-rich "black
shales" were widely deposited on Earth during the
Cretaceous Period. They are believed to be the result
of periods of reduced degradation rates of sedimentary
organic matter, which have been referred to as
Oceanic Anoxic Events (OAEs). The black shales are
one of the major source rocks for petroleum on which
modern civilization heavily relies.
To understand the cause and bigeochemical processes
of the OAEs, we have investigated black shales
from central Italy and southern France. In FY we
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δ 13 C (per mil)
Fig.28 Isotopic composition of organic carbon in the OAE2 black
shales from Central Italy (Kuroda et al., submitted). Arrows
indicate the clay layers that are substantially depleted in
13
C relative to adjacent layers.
obtained a high-resolution record of stable isotopic
compositions of total organic carbon through the
Livello Bonarelli black shale (OAE, Ma) and
found that thin (~cm) clay layers intercalate the black
shale and are depleted in C by as much as relative
to the adjacent layers (Fig.). This suggests that a
portion of the organic matter in the clay layer originates
from methane oxidizing bacteria. We are currently
analyzing biomarkers, pigments, and carbon isotopic
compositions of these molecules to further investigate
the paleoenvironment when the clay layers formed.
We have also investigated OAEb ( Ma) black
shales distributed in the Vocontian Basin, southern
France. In FY we performed stratigraphic
descriptions of the sequence and measured the carbon
isotope ratio of organic carbon in the black shale.
Analyses of major element compositions using the
newly established core-logger "Tatscan F" are currently
underway to achieve high-resolution mapping
of major elements in the black shale.
2.2. Model Ocean for Cretaceous OAEs
To estimate the Cretaceous OAE environments, we
are studying modern anoxic environments similar to
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