Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 8
1
INTRODUCTION
IMPETUS FOR THE WO~HOP
Plate tectonic theory created a revolution in our
understanding of both the present ocean basins and the ancient
continental interiors. The basic tenets of the theory have been
confirmed during two decades of intense exploration of the earth
using increasingly sophisticated techniques, but it remains
essentially a kinematic theory describing the motion of rigid
plates on a sphere and thus provides only a crude outline of how
plate boundarie-~--and hence continental margins--actually evolve.
These boundaries are, by their nature, a deforming continuum
governed by processes not directly addressed by plate tectonics
theory.
The last decade has seen a gradual transition in the focus
of continental margins research from an observation-oriented
endeavor to a more process-oriented study.
~ . . . . .
Phenomenological and
Descriptive studies are being complemented and extended by
physical, quantitative, and analytic models. Such models provide
specific predictions of measurable parameters, which can be
compared with field or experimental observations. In many cases ,
this approach has challenged or overturned older theories of
margin evolutions
The last decade has also seen a number of important advances
that have established a strong foundation for current and future
research at continental margins. Some of these advances are
listed here.
1. Seismic reflection methods and deep ocean drilling have
produced startling discoveries about the large-scale architecture
of continental margins.
2. Field studies of continental orogenic belts, both
extensional and contractional, have provided important insights
8
OCR for page 9
into tectonic processes operating within the submerged parts of
modern continental margins.
3. Geodynamic models are now capable of modeling in a
realistic fashion the mechanical and thermal processes associated
with lithospheric extension and contraction.
4. Research in rock mechanics has outlined first-order
processes governing frictional faulting and ductile flow of
rocks.
5. Seismology has developed inverse methods capable of
resolving the time evolution of the rupture process, which
provides direct information about the local structure of
seismically active faults.
6. Studies of trace element and isotope systematics in
igneous rocks have produced a set of tools for monitoring the
fluxes of mantle, crust, and sediment at volcanic arcs and at
magmatically active rifts.
7. Advances in the understanding of continental margin
depositional systems and the formation of large-scale
stratigraphy sequences now allow us to extract from the
stratigraphic record a detailed history of past climate and
tectonism.
These advances have led us to the brink of a new era in our
understanding of continental margins. Many of the advances,
however, have been made largely from within the confines of a
specific discipline , with little contribution from other fields.
Recognizing the current and future potential of continental
margins research, the Ocean Studies Board and the Board on Earth
Sciences jointly sponsored a workshop focused on this field. The
workshop was designed to take full advantage of the recent
advances. Participants were brought together from a broad range
of disciplines to discuss common interests, new developments, and
future directions for margins research. The objectives of the
workshop were: (1) to assess the state of knowledge and current
directions in continental margins research; (2) to identify areas
in which research is poised to make significant progress; and (3)
to design a strategy for the construction of a ~ong-term science
plan for margins research.
ORGANIZATION AND SUPPORT OF THE WORKSHOP
The Continental Margins Committee was formed as a steering
committee for the workshop e In advance of the workshop,
background papers were solicited and then distributed to the
participants. The papers summarized the current state of
9
OCR for page 10
research in specific areas and were used as springboards for
discussion (see Part III). The workshop was organized into two
sections: Pa~ssive Margins and Active Margins. Each section in
turn formed three working groups, which were assigned specific
topics within the broader context of continental margins
research.
The focus of each group was as follows:
Passive Margins
Group 1: Mechanics of Rifting and Associated Magmatism
Group 2: Rift and Passive Margin Basins: The Sedimentary
Record
Group 3: Post-Depositional Processes: Internal versus
External Processes in Passive Margin Sediments
Active Margins
Group 1: Mechanics of Plate Motion
Group 2: Geologic Evolution of Active Continental Margins
Group 3: Mass and Chemical Transfer
The opening afternoon of the workshop consisted of an
informal poster session in which recently acquired data and new
research developments were presented in a format conducive to
discussion.
The second day began with a joint plenary session of all
participants, during which the objectives of the workshop were
defined. The passive and active sections then met separately for
presentations by selected keynote speakers. Each speaker was
allotted 20 minutes for presentation, which was followed by 20
minutes of open discussion.
The participants then reconvened in a joint plenary session
in which the chairman issued a set of charges to the working
groups in the form of a list of questions.
CHARGES TO THE WORKING GROUPS
1. What is the single most important scientific objective
within the focus of your working group?
a. What are the critical problems?
b. What are the specific processes?
10
OCR for page 11
2. What studies are needed?
a.
be
3.
What data should be collected?
What laboratory, theoretical, and numerical
developments are needed?
What measurement capabilities are needed?
What strategies must be developed to achieve your stated
goals?
For the rest of the second day the participants split into
the six working groups, each of which also interacted extensively
with the others.
On the third day, the participants continued to meet in the
working groups and began writing the working group reports
included as Part TI of these proceedings. A combined session of
all participants was held at midday for presentation and
discussion of preliminary results. The remainder-of the day was
spent in the working groups.
-
The final morning of the workshop was divided between
worming group meetings and a plenary session of all participants.
In the plenary session, the results of each working group and the
links between them were presented and discussed.
. · —
These proceedings reflect the views expressed by the
workshop participants. The overall goals stated throughout the
report were derived from a consensus of the workshop but not
necessarily of the National Research Council.
11
Representative terms from entire chapter:
margins research
