Geology Reference
In-Depth Information
Fig. 12.10
GPR profi le showing a Holocence tidal inlet fi ll sequence at Plum Island, Massachusetts that coincides with late Pleistocene
drainage beneath the barrier. This former channel is imaged in offshore shallow-seismic records (From Hein et al.
2011
)
decreases upward (Israel et al.
1987
) . Shallow-seismic
profi les of inlet fi ll at Bolivar Pass reveal channel
stacking and cut-and-fi ll structures as well as perva-
sive westerly-dipping refl ectors (Siringan and
Anderson
1993
). These clinoforms dip from 0.5 to
4.6 degrees and are shallow dipping along the fl anks
and more steeply dipping toward the former incised
inlet channel. Inlet facies exhibit a high mud content
including muddy sand layers, mud lenses, mud clasts,
and mud-fi lled burrows. The muddy character of the
inlet fi ll has been explained by the low wave energy
and the contribution of mud to the coastal waters
from associated estuaries (Israel et al.
1987
; Siringan
and Anderson
1993
). In contrast, stacked tidal- inlet-fi ll
sequences at Mustang Island (10-15 m thick) consist
almost entirely of clean, well-sorted, fi ne quartz sand.
This sequence lacks shell hash, mud lenses, and
graded beds commonly associated with inlet depos-
its, because the sediment was sourced from reworked
mature barrier island sand devoid of shells (Simms
et al.
2006
). These studies of the Texas coast illus-
trate the importance of sediment source dictating the
character of the inlet fi ll deposits.
North and South Carolinas
The stratigraphy of the Outer Banks of North Carolina
is known from numerous coring studies (Moslow and
Heron
1978
; Susman and Herron
1979
; Tye and
Moslow
1993
; Culver et al.
2006
). This body of work
provides a basis for characterizing inlet deposits along
