Principal Investigators: James A. Austin, Craig S. Fulthorpe,
John A. Goff and Hilary Olson
Funded by: Office of Naval Research
Also check out the official STRATAFORM home page at University of Washington
A number of UTIG
investigators are involved in planning and executing this multi-year project, funded by
the Office of Naval Research. STRATAFORM consists of three distinct but inter-related
projects, whose objectives are to study: (1) shelf sediment dynamics and the development
of lithostratigraphy, (2) slope geological processes and resultant geomorphology, and (3)
stratigraphic sequences resulting from shelf and slope sedimentation. The overall goal is
to link short-term (i.e., acting over hours to weeks) biological and physical processes
affecting sedimentation (so-called "event" stratigraphy) to the sequence
stratigraphy and facies architecture of the preserved record (i.e., ~upper 100 m and
occurring over the past ~106 years).
UTIG is most heavily involved in the stratigraphic sequences project, which is attempting to understand the creation of the stratigraphic record on continental shelves and slopes as the product of geologic processes acting with spatial and temporal heterogeneities. Ultimately, modern processes are to be linked to the seismically imaged and sampled (i.e., preserved) record through an evolution of increasingly sophisticated models.
The key to this effort will
be the collection of "nested" geophysical and geological data, through use of a
variety of acquisition tools (multibeam seafloor mapping, multichannel seismic [MCS]
reflection, Huntec deep-towed single-channel boomer, coring, ocean drilling[?]), whose
individual temporal and spatial scales overlap to form a wide-ranging continuum of
measurements.
Two "natural labs" have been chosen by STRATAFORM: offshore New Jersey and northern California. The former is characterized by a modern depositional regime which is quiescent, but where Neogene to Pleistocene sequence stratigraphic geometries are well-developed. The latter is a tectonically active environment, where modern sedimentation is overwhelming the shelf. Comparing and contrasting these environments is the modern key to the inherently complex depositional patterns of the past.
The New Jersey continental shelf is of interest to the Office of Naval Research because
its subsurface is characterized by well-developed sedimentary geometries that record past
changes in sea level. In addition, a great deal of geophysical data has already been
collected across it, and it is proximal to some of the best oceanographic laboratory and
seagoing facilities in the U.S., making its repeated study as a "natural
laboratory" easy to achieve. This shelf has not received significant sediment input
for the past ~10,000 years, but existing seismic profiles have delineated two deposits of
older sediment, referred to as the mid- and outer shelf sediment wedges (see map above
left). These wedges have recently been imaged for the first time in 3D, using a very high
resolution, deep-towed seismic acquisition system. The purpose of these surveys was to
image the geology representing the last ~50,000 years of the margin's history in detail.
Nominal profile spacing was 10 m, with 2.5 m between shotpoints, both near the limits of
available navigational technology. Seismic measurements were so precise that they had to
be corrected for diurnal tidal effects <1 m in amplitude before the true geometry of
the sedimentary units could be observed.
Survey results show a
complicated system of sediment-filled channels meandering south-southeast in the general
direction of the modern shelf edge (see image left).
These channels, buried by ~5 m of younger sediment, are typically a few meters deep and 100-200 m across. They are related to the ancestral Hudson River drainage system and formed during glacial periods when the sea level was lower than at present, exposing the continental shelf. Core samples (see picture of corer above right) provide "ground truth" to verify the seismic results. Studies of such samples yield important information on ages of surficial sediments and environments in which they were deposited. Cores show that channels beneath the mid-shelf are cut into sediment >45,000 years old, and filled with muddy sediments as young as ~12,500 years (see seismic profile with core location below right). In contrast, channels on the outer shelf are filled with coarser, and probably older, sediments.
Scientific Objectives
The New Jersey studies are part of the ONR-sponsored STRATAFORM initiative, the
broad goal of which is to study the origin of the preserved stratigraphic record as the
product of short-term biological and physical processes that affect sedimentation. The
emphasis is on the upper 100 m of section and the last million years of Earth's history. 
The two "natural
laboratories" chosen for STRATAFORM, offshore New Jersey and northern California (see
map of sea floor bathymetry and reflectivity below), are characterized by fundamentally
different modern environments. The former is now quiescent, but stratigraphic geometries
are well-developed. The latter is geologically active: voluminous sedimentation,
punctuated by floods and modulated by storms, overwhelms the shelf. By using the northern
California margin as a modern analog for sedimentation processes active offshore New
Jersey in the past, the stratigraphic development of both margins can be studied
effectively. Only then can the value of the preserved geologic record for unraveling
recent Earth history, including assessments of anthropogenic influences on
naturally-occurring rates of climate change, be understood properly. UTIG researchers are
involved in operations on both coasts. Education and Training STRATAFORM and its companion program, AASERT
(administered by the Department of Defense), have been responsible for supporting four
M.A. candidates and one undergraduate in the Department of Geological Sciences at The
University of Texas at Austin. Another M.A. candidate from the University of Colorado at
Boulder has also been supported. Three of the four graduate students have participated in
seismic/coring acquisition efforts at sea as part of their training.
Significance
The most important aspect of the New Jersey research for the Navy is the
effects on the acoustics of shallow-water continental shelf environments of surficial
stratigraphic development and preservation. For seismic stratigraphers, the combined
high-resolution images and associated sampling control offer crucial information about the
history of sea level changes over the last 50,000 years. Since most of the US population
lives in coastal regions, global sea level rise, possibly induced or accelerated by human
activities such as the burning of fossil fuels, is an issue of growing concern. Any such
rise would have particularly severe impacts on Texas and other Gulf Coast states, which
have wide, low-lying coastal plains. In fact, a 1 meter rise in sea level could submerge
large parts of those coastal plains, and cities such as Houston, Corpus Christi and New
Orleans.
Recent Work
Some of our STRATAFORM projects include
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High-Resolution Seismic Surveying for Pleistocene Sequence Stratigraphy, New Jersey Continental Shelf and Upper Slope, in Support of STRATAFORM (STRATA FORmation on Margins) |
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High-Resolution Seismic Surveying for Neogene-Quaternary Sequence Stratigraphy, Northern California Continental Shelf and Upper Slope, in Support of STRATAFORM (STRATA FORmation on Margins) |
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Huntec 3-D Surveying and Piston Coring Off New Jersey |
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Huntec Surveying of Shelf Sites for the New Jersey/Mid-Atlantic Transect |
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Statistical Characterization of Bathymetry and Stratigraphy on Continental Margins |
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Site Survey Augmentation - Grab Sampling on the New Jersey Margin |
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Site Survey Augmentation - CHIRP Seismic Reflection on the New Jersey Margin |