CGS
Monthly Meeting
Tuesday, March 16,
2010
High-Resolution
Seismic Imaging, Basin
Sedimentation and
Paleoclimate Studies to
Further Investigate the
Remarkable Santa Barbara
Basin Record
by
Craig Nicholson1,
Richard Behl2,
James Kennett1,
Christopher Sorlien1,
Sara Afshar2,
Courtney Marshall2,
Carlye Peterson2,
Lorraine Lisiecki3,
Mike Barth4
and the SBCore Team
Abstract:
Santa Barbara Basin
provides one of the
highest-resolution
paleoclimate records of
the late Quaternary ever
recovered from the
world’s oceans. Its
unique geologic,
tectonic, and
oceanographic setting
has resulted in a small
well-defined bathymetric
basin that has proven
highly sensitive for
recording detailed
changes in global
climate and at a
resolution similar to
Greenland ice cores.
Over much of the basin,
sedimentation rates are
remarkably high (>1 m/kyr),
exhibit a relatively
constant spatial pattern
defined by local
tectonics, and are
largely unaffected by
orbital through
millennial-scale
climatic oscillations.
Multichannel seismic
(MCS) reflection and
industry well data
indicate that, in
several areas,
continuous,
late-Quaternary
sediments deposited in
the deep
paleobathymetric basin
were subsequently
uplifted, folded, and in
places eroded across
various young, active
fault-related fold
structures. These older
strata were mapped in 3D
to seafloor outcrop,
where they are now
accessible to piston
coring. In 2005, we were
able to systematically
recover substantial
sections of these older
sequences back to ~700
ka. Oxygen isotopic
studies confirm the
presence of millennial
and sub-millennial-scale
climatic oscillations
similar to those that
mark the latest
Quaternary. This
includes abrupt
decadal-scale warming
events (both onset and
termination), climate
flickering, and––in our
~700 ka core––a
remarkably periodic
(~1200 yr)
millennial-scale climate
oscillation never before
observed owing to the
previous lack of
paleoclimate records of
sufficient age and
resolution. In several
cores, sediment material
properties, including
acoustic impedance,
density and total
organic carbon exhibit a
remarkable correlation
with inferred
paleoclimate
oscillations. This
correlation suggests
that basin-scale
variations in sediment
composition and fabric
produced by climatic
forcing during
deposition are
surprisingly still well
preserved, and that
geophysical techniques
like seismic profiling
and core logs may
provide valuable
preliminary estimates of
past climate behavior
and the quality of the
potential core record
prior to conducting more
extensive,
labor-intensive isotopic
analyses. In November
2008, a second,
high-resolution MCS site
survey and piston coring
cruise was conducted to
further extend this
remarkable record and to
test the basin’s
continued sensitivity to
global high-frequency
climatic oscillations
back through the
Mid-Pleistocene Climate
Transition (~800 ka to
1.2 Ma). Results confirm
the viability of
proposed deeper coring
by the Integrated Ocean
Drilling Program (IODP)
to recover a continuous,
complete
ultra-high-resolution
global climate record
back to about 1.6 Ma.
1 Marine
Science Institute, UC
Santa Barbara
2 Department
of Geological Sciences,
CSU Long Beach
3 Department
of Earth Sciences, UC
Santa Barbara
4 Sub-Sea
Systems, Inc., Ventura
Biography:
Craig Nicholson has
degrees from Amherst
College, St. Louis
University and
Columbia University.
His primary areas of
research are
earthquakes, active
faulting and tectonics.
His current research
involves mapping the
distribution of active
faults, folds and
sedimentary basins
offshore of
southern California,
and most recently,
helping fellow
geologists extend the
high-resolution global
climate record located
in
Santa Barbara Basin.
Craig is a Research
Geophysicist with the
Marine Science Institute
and
Adjunct Associate
Professor with
the Department of
Earth Science at
UCSB, where he has been
since 1988.