478
important question regarding the sensitivity of fluvial systems to base-level change. In the most proximal exposures of the Castlegate Sandstone (Fig. 9.18;
joes Valley, Price Canyon) there appears to be only a
single sequence, of probable third order, according
to the chronostratigraphic reconstruction of Fouch
et al. (1983). These beds appear to correlate with a
succession of higher-order sequences in the coastal
plain area (Trail Canyon and points east). The updip
merging of these higher order sequences into a single
undifferentiated succession may be interpreted in
one of at least two ways: (a) Fluvial systems are
relatively insensitive to base-level change, the effe cts
of which disappear updip; or (b) the Castlegate
stratigraphy may be controlled by more than one
Sequence Stratigraphy
process, such as third-order tectonism (fluvial rejuvenation, changes in sediment supply), especially in
updip regions, and a fourth-order cycle of base-level
change, of tectonic or eustatic origin, which is most
pronounced in coastal areas. Local complications
arise. in this particular case, because the downdip
areas (Trail Canyon and areas to the east) are underlain by the Late Paleozoic evaporites of Paradox
Basin, and the effects of contemporaneous salt tectonics may have been significant. This should serve
to remind us that in each real-life case study, the
lessons to be learned from theoretical or numerical
models must be tempered by the practicalities of the
given basin setting, with its inherited crustal heterogeneity and history of subsidence and tectonism.
important question regarding the sensitivity of fluvial systems to base-level change. In the most proximal exposures of the Castlegate Sandstone (Fig. 9.18;
joes Valley, Price Canyon) there appears to be only a
single sequence, of probable third order, according
to the chronostratigraphic reconstruction of Fouch
et al. (1983). These beds appear to correlate with a
succession of higher-order sequences in the coastal
plain area (Trail Canyon and points east). The updip
merging of these higher order sequences into a single
undifferentiated succession may be interpreted in
one of at least two ways: (a) Fluvial systems are
relatively insensitive to base-level change, the effe cts
of which disappear updip; or (b) the Castlegate
stratigraphy may be controlled by more than one
Sequence Stratigraphy
process, such as third-order tectonism (fluvial rejuvenation, changes in sediment supply), especially in
updip regions, and a fourth-order cycle of base-level
change, of tectonic or eustatic origin, which is most
pronounced in coastal areas. Local complications
arise. in this particular case, because the downdip
areas (Trail Canyon and areas to the east) are underlain by the Late Paleozoic evaporites of Paradox
Basin, and the effects of contemporaneous salt tectonics may have been significant. This should serve
to remind us that in each real-life case study, the
lessons to be learned from theoretical or numerical
models must be tempered by the practicalities of the
given basin setting, with its inherited crustal heterogeneity and history of subsidence and tectonism.