Geology Reference
In-Depth Information
consist of planar to cross-bedded, well-sorted sand that
fi nes upward in contrast to the barrier lithosome.
Inactive fi lls and inlet deposits such as those from Texas
and Louisiana coasts contain substantial mud units.
Ebb- and fl ood-tidal deltas are relatively thin deposits
and are composed of planar to cross-bedded fi ne to
medium sand. Their structure is controlled by the rela-
tive activity of channelization, migration, and closure,
bedform and swash bar migration, and wave and tidal
sedimentation. Preservation of tidal-inlet and associ-
ated deposits, that form a number of important petro-
leum reservoir sequences, is generally high in regressive
sequences, but lower in rapidly transgressing systems
due the depth of shoreface erosion, a process that tends
to remove all but the deepest parts of inlet channels.
Confi rmed and suspected inlet fi lls on the inner shelf all
occur offshore of barrier systems having deep inlet
channels (>15 m). Recent advances in subsurface imag-
ing and facies analysis are opening new frontiers in
understanding the geological legacy of tidal inlets.
References
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Angulo R, de Lessa GC, Souza MC (2006) A critical review of
mid- to late-Holocene sea-level fl uctuations on the eastern
Brazilian coastline. Q Sci Rev 25:486-506
Ashley GM (1990) Classifi cation of large-scale subaqueous
bedforms: a new look at an old problem. J Sed Petrol
60:160-172
Barwis MJH (1978) Recognition of ancient tidal inlet sequences:
an example from the Upper Silurian Keyer Limestone in
Virginia. Sedi 25:61-82
Barwis JH, Hayes MO (1979) Regional patterns of modern bar-
rier-island and tidal inlet deposits as applied to paleoenviron-
mental studies, in Ferm JC, and Horne JC, (eds., Carboniferous
Depositional Environments in the Appalachian Region:
Columbia, South Carolina, Carolina Coal Group, pp 472-508
Belknap DF, Kraft JC (1981) Preservation potential of transgres-
sive coastal lithosomes on the U S Atlantic shelf. Mar Geol
42:429-442
Belknap DF, Kraft JC (1985) Infl uence of antecedent geology on
stratigraphic preservation potential and evolution of
Delaware's barrier systems. Mar Geol 63:235-262
Boothroyd JC (1985) Tidal inlet and tidal deltas. In: Davis RA Jr
(ed) Coastal sedimentary environments. Springer, New York
Boothroyd JC, Hubbard DK (1975) Genesis of bedforms in
mesotidal estuaries, in Cronin JE (ed), Estuarine research, Vol.
2, Geology and engineering: New York, Academic Press,
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Boothroyd JC, Friedrich NE, McGinn SR (1985) Geology
of microtidal coastal lagoons: Rhode Island. Mar Geol
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Bridges PH (1976) Lower Silurian transgressive Barrier islands,
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Fig. 12.21
Examples of sediment removal at Zoutkamperlaag
Inlet showing that little of the drainage network is preserved under
moderated shoreface erosion scenarios (From Reiu et al. 2005)
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migration can signifi cantly alter inlet shoreline
sedimentation processes.
Tidal-inlet fi ll comprises substantial portions of bar-
riers in mixed-energy settings and typically a greater
fraction of wave-dominated settings due to higher fre-
quency of inlet migration, barrier breachings, and clos-
ings. Inlet fi lls are recognized by the coarse, shell-rich
nature of their basal unit forming a sharp contact with
underlying sediment. Active inlet fi ll sequences thin in
both a landward and seaward direction and commonly
