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Pleistocene
Lake Bonneville was the most prominent feature of the eastern Great
Basin during much of the Late Pleistocene. During lake high stands,
a variety of sedimentological and geomorphic features formed in response
to circulation, river runoff, and wave action. These features fall into
three basic categories. (1) Common shoreline features such as drift-aligned
sand and gravel bodies such as baymouth barriers and spits (e.g., the
Stockton bar), cuspate barriers (e.g., Point of the Mountain), tombolos,
and sand delta terraces that prograded basinward during the regression
of Lake Bonneville. (2) Unusual "dumps" of Gilbert-type delta sediments
(e.g., Big Cottonwood Canyon gravels) which can be laterally extensive.
(3) Marls, and other fine-grained offshore facies with some sediments
reworked during lower lake levels. Understanding the genetic mechanisms
operative during formation of these deposits has important engineering
implications. For instance, liquefaction potential of the offshore facies
is directly related to the relative amount of coarse-grained sediment
supplied by rivers which in turn is a function of runoff intensity and
sediment dispersal by lake currents. Numerical modeling studies of Lake
Bonneville are being used to establish relationships between the field
features of the lake and specific hydrodynamic characteristics which
in turn are a function of Late Pleistocene climate forcings in the Great
Basin. These studies have the potential for predicting a number of features
of interest to engineering geologists working in the Bonneville basin.
Along the eastern
margin of the Basin and Range province, the Wasatch Front of Utah is
replete with geoantiquities, including Lake Bonneville deltas, spits
and bars, glacial moraines, alluvial fans and debris flows, fluvial
terraces, fault scarps, modern lakeshores, playas, and salt flats. These
features are situated in a region where current and anticipated population
growth rates are double the national average. Geoantiquties of this
area are well positioned to chronicle the evolution of the pre-urban
landscape, but are poorly positioned to withstand the impacts of urbanization.
We are using geographic
information systems (GIS) to integrate inventories of geoantiquties
and models of Wasatch Front urban growth in order to plan mitigation,
scientific investigation, education, information transfer, and conservation.
Partnerships with government agencies, educational institutions, non-governmental
organizations, public interest groups, and committed individuals provide
pathways to raise awareness and produce broad involvement in planning,
and participation in implementing geoantiquities resource management.
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