Geology Reference
In-Depth Information
Fig. 17.22
Transgressive tidal accumulations in incised valleys
are relatively common in the Western Interior Seaway succes-
sion, e.g. through the Campanian Blackhawk Formation, Book
Cliffs, Utah, USA (From Hampson et al.
2008b
, after Balsley
1980
; Hampson and Howell
2005
). Note that the valley abun-
dance and depth increases upwards, from higher to lower accom-
modation settings
incisions, but the incisions have not been interpreted as
an incised valley base (Birgenheier et al.
2009
) . These
two accumulations are in the Masuk Formation and
Muley Canyon Sandstone in SE Utah. These accumu-
lations are 5-25 and 5-15 m thick respectively, and
interpreted as transgressive tide-infl uenced fl uvial,
lagoonal and tidal channel deposits that overlie fl uvial
incisions associated with a seaward shift of facies
(Birgenheier et al.
2009
) .
SW Wyoming and NE Utah, where it occurs as a 60 m
thick stack of estuarine deposits (Plink-Bjorklund
2008
;
Fig.
17.23
, Table
17.3
). The lowermost of the four
vertically stacked tide-dominated estuarine units (units
overlying TR2-5 in Fig.
17.23
) is an erosional remnant
and only 10 m thick, whereas the subsequent three units
are 17, 24 and 22 m thick. Each of these units has a tidal
ravinement surface at its base, and is overlain by a
landward-stepping lower part and by an aggradational
and partially (in inner- and central-estuarine zone)
seaward-stepping upper part. This vertically stacked
tide-dominated estuarine succession is not confi ned by
a valley, nor is it based by a fl uvial incision surface.
Instead the four stacked units refl ect repeated tidal
ravinement, reshaping of the river mouth, and succes-
sive
in situ
infi lling (Plink-Bjorklund
2008
) . The four
vertically aggrading units consist of tide-dominated or
17.4.3 Thick Non-valley-confi ned
Transgressive Tidal Accumulations
This third, transgressive tidal setting is the most uncom-
mon, and is documented in the uppermost part of the
Chimney Rock Sandstone of the Rock Springs Fm in
