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Morphodynamics and Facies
Architecture of Tidal Inlets
and Tidal Deltas
Duncan FitzGerald , Ilya Buynevich ,
and Christopher Hein
Abstract
Tidal inlets are highly dynamic systems marking positions along barrier coasts
where dominant wave and longshore sand transport processes are juxtaposed with
a tide-dominated regime in which onshore-offshore sand movement is manifested
in the formation of fl ood- and ebb- tidal deltas. The morphodynamics of tidal
inlets and distribution of their associated sand shoals are governed by the tidal
prism, wave versus tidal energy, and the regional geological framework. Sand that
is delivered to the inlet channel via longshore transport can be sequestered in the
backbarrier, moved onto the ebb-tidal delta, or can bypass the inlet. Such bypass-
ing is accomplished through wave and tidal processes and ultimately results in the
landward migration and welding of large sand bar complexes to the downdrift
shoreline. Tidal inlet-fi ll deposits typically exhibit a sharp basal contact with
underlying units and consist of a fi ning-upward sequence in contrast to the gener-
ally coarsening-upward barrier lithosome. The preservation potential of inlet and
associated tidal-delta deposits is high in regressive sequences, but relatively poor
in transgressive systems due to the shallow nature of inlet-fi ll deposits compared
to the base of the erosional wave- or tidal- ravinement surfaces. Exceptions occur
in paleotidal inlet regions having large bay tidal prisms and deep inlet channels.
Although tidal-inlet deposits have been reported in the rock record and may serve
as important petroleum reservoirs, to date they are not readily recognized.
High-resolution geophysical and sedimentological research of both active and
relict inlets is providing a wealth of information necessary to improve the inlet
facies models for ancient sedimentary sequences.
12.1
Introduction
Tidal inlets are openings along barrier coasts through
which tidal waters penetrate the land, thereby providing
a hydraulic connection between the ocean and bays,
lagoons, and marsh and tidal creek systems. Inlets are
societally important because they provide a pathway
