Sedimentology and Ichnology in Mixed-Energy Coasts
Yang, ByongCheon1,
Although coastal environments and
associated deposits are extremely diverse, sedimentological
models simply develop the notion that coastal deposits can be identified as
wave- and tide-dominated settings that are distinctive in terms of physical
processes and geomorphology. Thus, these two settings are characterized by
distinctive sedimentary facies. Muddy heterolithic facies are thought
to characterize tidal-flat deposits, whereas wave- and storm-generated
deposits, including hummocky cross stratification (HCS), are likely to be
representative of shoreface settings.
Recent coastal studies from
However, we show that the integration of ichnological and sedimentological
data has produced new criteria for the identification of open coast tidal flat
deposits. These are: (1) tidally modulated rhythmic deposits that reflect the continuous
change in wave energy due to water-level fluctuation; (2) a number of swash
bars (> 4) are much more abundant, compared with those in foreshore (<
3); (3) the HCS wavelength decreases systematically landward due to a decrease
in bottom orbital diameter; (4) overall a higher abundance of animal traces
compared to the upper shoreface and foreshore of
wave-dominated settings; and (5) ichnological trends
might be not necessarily perpendicular to the direction of wave energy.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California