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Chapter 3
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Stratigraphy
and Facies Architecture of  Parasequences with Examples from the Spring
Canyon Member, Blackhawk Formation, Utah
Diane L. Kamola
Department of Geological
Sciences
Old Dominion University
Norfolk, Virginia, U.S.A.
John C. Van Wagoner
Exxon Production Research
Company
Houston, Texas, U.S.A.
*
ABSTRACT
Parasequence architecture and the nature
of parasequence boundaries in marine to nonmarine strata are well illustrated
in the Spring Canyon Member of the Upper Cretaceous Blackhawk Formation.
Parasequences and parasequence sets are stratal successions which are the
building blocks of sequences. In marine strata, parasequences result from
basinward progradation of the shoreline, and typically shallow and coarsen
upward; in the nonmarine, parasequences show a distinct vertical facies
succession which begins with lagoon-fill deposits and ends with freshwater
coals. A flooding surface (parasequence boundary), indicating an abrupt
increase in water depth, accompanied by minor submarine erosion and nondeposition
separates individual parasequences within a parasequence set. The parasequence
boundary is a continuous, single surface that can be traced from updip
in the coastal plain to downdip in the distal shelf. The parasequence boundary
has different physical expressions depending on where it is observed, and
enables correlation of nonmarine/marginal marine rocks to coeval marine
strata within the same parasequence. Parasequence evolution and depositional
reconstruction is dependent on the application of sequence stratigraphic
concepts. Outcrop examples from the Spring Canyon Member document parasequence
expression. Both wave-dominated shoreface sandstone and river-dominated
deltaic sandstone exist laterally in the marine portion of the same parasequence.
Both are terminated by a flooding event marked by a rapid landward shift
in facies, with no transgressive lag. A number of marginal marine and nonmarine
subenvironments exist laterally within the same parasequence. The parasequence
boundary provides a |
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