Siliciclastic systems are
lumped into wave- or tide-dominated classes, and many detailed facies and
sequence-stratigraphic analyses interpret pronounced changes to a shift from
one to the other caused by major (commonly external) perturbations. To explore
fundamental assumptions of some of these studies, Legler et al. document distal
deposits near the pinchout of the widely studied lower Sego Sandstone in the
Book Cliffs, western Colorado, a unit generally regarded as the type example of
an ancient tide-dominated delta. The analysis of facies and stratigraphic
architecture suggests that coeval waves and storms were equally prominent in
controlling its deposition. The re-interpretation of the lower Sego Sandstone
as a mixed, tide- and wave-influenced delta is important in three ways: (1) the
prevailing, widely used archetype of an ancient tide-dominated delta should be
viewed as recording a wider mixture of depositional processes; (2) the
recognition that wave- and tide-dominated deposits can be coeval; and, as a
result, (3) sequence stratigraphic framework of the lower Sego Sandstone and
other ancient tide-dominated/influenced, regressive strata may need to be
re-assessed.
Facies relationships and stratigraphic architecture of distal, mixed tide- and wave-influenced deltaic deposits: lower Sego Sandstone, western Colorado, U.S.A. by Berit Legler, Gary
J. Hampson, Christopher A.L. Jackson, Howard D. Johnson, Benôit Y.G. Massart,
Marcus Sarginson, and Rodmar Ravnås
No comments:
Post a Comment