Workshop
on Climate-Tectonic Drilling in Southeast Asia
June 5-7th
2006, Kochi, Japan
Planning for Integrated Ocean
Drilling Program and International
Continental Drilling Program operations in SE Asia
An InterMARGINS sponsored Workshop
Read the Meeting Report (pdf file)
Download the abstracts for scheduled
presentations
Interactions
between the solid earth and the global climate system are a frontier
area for ocean and earth science research and have been highlighted as
a focus area for the Integrated Ocean Drilling Program (IODP). Of
all
the possible links between these earth systems the proposed
associations between the elevation of the Tibetan Plateau and the
strength of the Asian monsoon is one of the most dramatic and
controversial. Testing and quantifying these proposed links
requires
independent records of the evolving climatic, tectonic and erosional
histories that can be correlated, or not in order, in order to
determine how these systems are linked over long periods of geologic
time. The most complete sedimentary records necessarily lie offshore on
the continental margins where sediments preserve evolving erosional
flux since the start of India-Asia collision, around 50 million years
ago. Although the continental record can be an important part of the
system the large volume of eroded material and the relative lack of
accommodation space onshore necessarily results in most material
eventually being deposited offshore.
Satellite image of the Gulf of Tonkin
and eastern Tibetan Plateau, the source of the Red River, which follows
the trace the giant strike-slip fault, the Red River Fault up to the
flanks of the plateau. The marine record of erosion by the Red
River is the key to reconstructing the uplift history of eastern Tibet
and the drainage captures associated with that process (Photograph is
from Visible Earth, NASA)
A
workshop is to be held to explore the potential of using the Red River
system as a means to understand climate-tectonic interactions in
Cenozoic Asia. The Red River is selected because it derives sediment
directly from the flanks of eastern Tibet. Its marine delta and
fan should preserve sediment that can provide a relatively simple
erosional history, which can be used to constrain the growth of the
plateau. In addition, the Red River is sited on the southeastern
part of the Tibetan Plateau and is believed to have once been a much
larger system that was reduced through time as drainage capture
transferred the original headwaters to other major rivers in Asia
(e.g., Mekong, Yangtze, Salween). Since then its drainage system
has been influenced by the Asian Monsoon that is considered to be
linked to Tibetan surface uplift. If these capture events can be
dated then these can be used to constrain the elusive uplift of Tibet.
Although IODP drilling has already been proposed for the Yinggehai-Song
Hong Basin that lies between Hainan Island and Vietnam we aim to use
the workshop to sharpen the science objectives of this work and
specifically to see how the marine drilling might be augmented by
additional programs such as continental drilling (ICDP) and land-based
field geology.
Workshop Plan
We propose to host a workshop for 30-40 scientists at the Corestore and
Laboratory facility of IODP, newly opened at Kochi, Japan. We invite
participants from all IODP member countries, as well as scientists from
the South China Sea region, and those working onshore. The meeting will
take place on 5-7th June 2006 and will have the following
objectives:
1)
Review what is presently known about the marine geology of the
Yinggehai-Song Hong Basin, the tectonics of the Red River Fault Zone
and the uplift of eastern Tibet. The climatic history of the
region will also be reviewed and current climate models linking the two
will be assessed.
2)
Assess the major scientific goals and the data sets that will be
required to answer outstanding questions. Discuss where such data
sets can best be generated.
3)
Present existing drilling proposals for climate-tectonic drilling
in Asia, especially in the South China Sea and discuss whether the
proposed locations are optimally located to address the science
goals. Additional offshore and onshore drilling targets will be
proposed and discussed.
4)
Additional non-IODP scientific programs that are needed to
complete the project will be determined. These will likely include
cooperation with IGCP projects, International Continental Drilling
Program (ICDP) for possible drilling of the Hanoi Basin, as well as
integrating with previously scheduled ICDP work in the Qinghai
Lake. Work on the tectonics and geomorphology of eastern
Tibet will be important to understanding the offshore record.
Characterizing the geochemistry and thermochronology of the potential
source regions, as well as the modern river fluxes will be important to
developing the provenance tools needed to test the capture hypothesis.
5)
Review the status of potential site survey data, especially
seismic reflection data from the offshore in order to determine what if
any data will be needed to permit the first phases of drilling to be
scheduled. In doing this we draw on both academic and industrial
expertise from the region.
Shaded
bathymetric-topographic map of the Red River delta area showing
the location of the proposed drill sites, as well as the main
geographic features in the drainage. The erosion of eastern Tibet by
the Red River even at the present time is clear.
Role of Asian Rivers
Use of
the marine erosional record to reconstruct surface uplift is
complicated because erosion may document exhumation, but this is not
equivalent to surface uplift (England and Molnar, 1990). Although
western and central Tibet are internally drained and are mostly
uneroded, the eastern edge of the plateau is strongly incised by the
major rivers of east Asia, many of which are sourced in Tibet, e.g.,
Yangtze, Mekong, Salween, Irrawaddy and Red). Surface uplift of Tibet
will affect sediment flux from the rivers in a number of ways. The
excavation of the Tibetan river gorges should be linked to initiation
of surface uplift in eastern Tibet, sending a sediment pulse into the
Asian marginal seas. In addition, the progressive eastward growth of
the Tibetan Plateau (e.g., Clark and Royden, 2000), and the NE-ward
propagation of the Namche Barwa syntaxis (Burg et al., 1998), has
resulted in the diversion of pre-existing river systems and the
progressive capture of drainage basins from one river to another (Clark
et al., 2000, 2004) resulting in changing marine clastic accumulation
rates, independent of the rate of sediment production in the sources.
The third major link between marine sedimentation and plateau uplift is
that provided by strengthening of the Asian monsoon. Although debate
continues as the relative importance of tectonically-driven uplift and
precipitation in controlled erosion (e.g., Burbank et al., 2003), many
workers implicate precipitation as a major, maybe dominant control to
erosion (e.g., Dadson et al., 2003; Wobus et al., 2003). There is thus
good reason to expect a marine record of plateau surface uplift
offshore the Red River delta.
|
Major drainage
basins in East Asia showing the potential for drainage capture around
the eastern syntaxis of the Himalaya where many river courses run
parallel and close together. I the model of Clark et al. (2004) much of
the upstream portions of the rivers once flowed into the South China
Sea through the Red River which is now a small fragment of the original
system. Progressive drainage capture was driven by uplift of the
eastern flank of the plateau due to lower crustal flow. Figure produced
by Marin Clark (Caltech).
|
In order to
reconstruct the drainage evolution and date plateau surface uplift a
proposal has already been submitted to IODP to examine the evolving
provenance of the marine sequences accumulated where the Mekong and Red
Rivers reach the sea. These systems to be the most appropriate for
drilling because ODP Leg 184 already provides some control on clastic
flux from the Pearl River (Clift et al., 2002b). The Yangtze is not
suitable for study at this time because of large-scale sediment
sequestering onshore in Eastern China, poor offshore stratigraphic
control, and because of evidence to suggest that this may be a
relatively young river, possibly only dating from the early
Pleistocene. Unlike the Indian Ocean rivers, whose clastic flux is
strongly influenced by the Himalaya, the Asian rivers including Mekong
and Red Rivers provide a much clearer erosion signal of the Tibetan
Plateau. The Red River in particular is significant because of its
proposed role as the ancestral river of SE Asia (Clark et al., 2004).
Asian Monsoon
The Asian monsoon dominates the climate and oceanography of East
and SE Asia. Understanding how monsoon strengthening relates to
regional tectonism, erosion and the margin stratigraphy over long
periods of geologic time is a key goal of IODP and related studies in
the Red River region. Although the variability of the monsoon on
orbital time-scales has improved, especially in the South China Sea
following ODP Leg 184, the longer-term evolution remains enigmatic. On
long time scales Kroon et al. (1991) and Prell et al. (1992) noted a
marked increase in the percentage abundance of G. bulloides at ~8.5 Ma
in the Arabian Sea, and Prell et al. (1992) called attention to
qualitative changes in abundance of some radiolaria at roughly the same
time. As these proxies are related to modern monsoonal strength these
workers suggested that the monsoon strengthened at ~8.5 Ma, at least in
South Asia. More recently An et al. (2001) used a compilation of
Chinese eolian dust records, together with similar marine data from the
North Pacific to indicate initial strengthening of the Indian and East
Asian monsoons at 8–9 Ma, and especially after 4 Ma. However, consensus
on the nature of climate evolution has yet to be achieved. In the South
China Sea evolving clay mineralogy suggests a switch from a drier to a
wetter climate before 15 Ma (Clift et al., 2002b). Even earlier
development of the monsoon is now proposed by Guo et al. (2002), who
showed that the eolian loess of central China does not date from 8 Ma
as previously believed but locally pre-dates 22 Ma. An even older
origin for the monsoon at ~30 Ma has been proposed and linked with the
retreat of shallow seas in central Asia (Ramstein et al. 1997). Thus
timing of initial monsoon strengthening is still far from being
accurately constrained and would be a major advance in our
understanding of the global climate system.
Interested parties are invited to contact the conveners for further
details.
Download a flyer about ICDP activities
Conveners
Peter Clift
Department of
Geology & Petroleum Geology
University of
Aberdeen
Meston Building,
Kings College
Aberdeen, AB24
3UE
United Kingdom
Wonn Soh
IFREE
Japan Marine
Science and Technology Center (JAMSTEC)
2-15
Natsushima-cho,
Yokosuka
237-0061,
Japan
Site maintained by Peter Clift
Last updated 18th May 2006
