[IRIS] AGU Session T14 - A Geologic Framework for EarthScope's USArray

[IRIS]

We would like to draw the community’s attention to a Fall06 AGU session
and a Town Hall meeting that focus on the emerging Geologic Framework  
for
EarthScope’s USArray initiative. These opportunities are summarized  
below.
We hope to have a morning oral session followed by an afternoon poster
session. We anticipate that the session(s) will be scheduled on  
Thursday,
December 14th, which is the day of the Town Hall session.

Ben van der Pluijim, Basil Tikoff, and Randy Keller

Session T14 - A Geologic Framework for EarthScope’s USArray

The Geologic Framework for EarthScope’s USArray initiative is a new
geologic venture that focuses on the construction, stabilization, and
modification of the North American continent through time.  The
initiative’s goals can be achieved through systematic integration of
geologic knowledge with the unprecedented Earth imaging to be collected
under the USArray program of EarthScope. The initiative encourages a
cooperative community approach to collecting and sharing data and will
take a coast-to-coast perspective of the continent, focusing not only on
the major geologic provinces, but also on the boundaries between these
provinces.

The purpose of this session is to examine current and future research in
the areas identified in a recent EarthScope workshop (a superswath
including Cascadia, the Northern Rockies, the Black Hills/Great Plains,
the Superior Province in the US, the Mid-Continent region, and the
southern Appalachians and a long swath along the Walker Lane trend; see
descriptions below and EOS v. 87, p. 221-223, 2006) and to provide a  
forum
for the community to define specific research areas and topics, and to
identify key research questions.

Target Areas:
1. Cascadia: The Pacific Northwest offers the best place in the
conterminous United States to investigate an active subduction zone, the
process of magmatic addition to the continental crust (Cascadia arc,  
High
Lava Plains, Idaho batholith), and the interaction of deformation and
magmatism. This is also potentially the best area in the North American
Cordillera to study tectonic accretion and subsequent modification of  
the
lithosphere.
2. Northern Rockies: The Northern Rockies have a diverse and extensive
geologic history that is recorded in rocks that range from ancient (>3.5
billion years old) gneisses of the Wyoming Craton to the modern
Yellowstone hot spot/Snake River Plain. environment.
3. Black Hills/Great Plains: The Black Hills is a type locality of
intracratonic deformation, allowing investigation of how
displacements/stresses are transferred far into the continental  
interior.
4. Superior: Located in the Lake Superior Region, this area will allow
investigation of the amalgamation of Proterozoic (750 million- to 2.5
billion-year-old) terranes to an Archean (older than 2.5 billion years
old) margin and the nature of an Archean tectosphere/Proterozoic
lithosphere boundary. The Midcontinent rift cuts both Archean  
tectosphere
and Proterozoic lithosphere, allowing investigation of how both of these
fundamental lithospheric types are altered by superimposed tectonism and
magmatism.
5. Midcontinent: This area encompasses the Ozark Plateau, the  
Mississippi
Embayment, the New Madrid seismic zone, and the Illinois Basin, which
allows scientists to address many questions pertaining to the  
assembly and
behavior of the North American craton.
6. Appalachians: Studies of the Appalachian region allow scientists to
investigate the assembly and breakup of supercontinents through two  
major
cycles; specifically, the Proterozoic breakup of the Rodinia
supercontinent and the Paleozoic-Mesozoic assembly/breakup of the Pangea
supercontinent.
7. Walker Lane: The Walker Lane Belt, situated in the western Basin and
Range province, will seamlessly integrate surface geology,  
topography, and
the history of the continental lithosphere with ongoing processes in the
Earth’s mantle.
8. Xenoliths: Collaborative, integrated studies of mantle and crustal
xenoliths, or inclusions of other rock types into igneous intrusions,  
will
provide an essential context for both the geologic and geophysical
observations of USArray.

Study of the seven regions should proceed in an intensified fashion, in
concert with planned USArray steps, such as the 'BigFoot' array,
consisting of broadband seismometers spaced every 70 kilometers.
Specifically, this stage of investigation would entail map-scale
'densified' arrays of passive source seismic receivers ('LittleFoot'
array, a set of ~400 broadband seismometers) and associated active  
source
seismic studies and complementary geophysics, in conjunction with
geologically based synthesis and targeted studies.

Town Hall Meeting; Thursday, December 14

Co-sponsored by IRIS, Tectonophysics Section, Seismology Section and
Volcanology-Petrology-Geochemistry Section

The Geologic Framework for EarthScope’s USArray initiative focuses on  
the
4-D construction, stabilization and modification of the North American
continent, through integration of geology and geophysical imaging under
EarthScope.  The initiative encourages a cooperative community  
approach to
collecting and sharing data, and takes a connected, coast-to-coast
perspective that examines fundamental processes, the continent’s major
geologic provinces and their boundaries. The town hall meeting will
discuss progress toward a national plan, examine opportunities for
interested US geoscientists and explore the initiative’s significant
education and outreach potential. (see also EOS v. 87, p. 221-223,  
2006).