Geology Reference
In-Depth Information
Fig. 7.7
Stratigraphic succession models for three major
tide-dominated delta systems, (
a
) the Ganges-Brahmaputra,
(
b
) the Mekong, and (
c
) the Changjiang. Each model includes
the lower coarsening-up subaqueous clinothem overlain by the
upper, generally fi ning-up, subaerial clinothem. The Mekong
example also shows an alternate coarsening-up model that is
characteristic of more wave-infl uenced portions of the delta
where beach ridges are well developed at the shoreface
(Modifi ed after Kuehl et al.
2005
; Ta et al.
2002
; Hori et al.
2002a
, respectively)
Offshore facies associations are less frequently
described for tide-dominated deltas, in part because of
sampling constraints in modern examples, but also
because tidal signatures become increasingly weak
offshore and may not be recognized in the rock record.
This potential bias may explain early confusion with
interpreting the Sego sandstones (Book Cliffs, USA),
which are incised into marine shales and thus described
