Environmental Engineering Reference
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Each of the three Lower Muschelkalk units contains shallowing-upward
cycles and terminates with two or three major carbonate sand bodies at the
top. Facies patterns from outer to inner ramp suggest a prograding shoreline,
of which the bioclastic Terebratula Beds in the middle unit represent shoal
deposits in a relatively distal position, whereas the Oolite Beds of the lower unit
and the Schaumkalk Beds of the upper unit are proximal. Because the inner
ramp facies between the coupled shoal deposits is more restricted (and partly
lagoonal) than the mid-ramp facies, it is concluded that drowning of the first
barrier resulted in subsequent deposition of lagoonal and tidal deposits, before
the now proximally positioned second barrier prograded over the system again
(cf. Burchette et al., 1990 ; see Knaust, 1997 ).
5. NEOICHNOLOGICAL APPROACHES
5.1 Rimmed Carbonate Platforms: Quaternary of the Bahamas
The islands and shallow subtidal platforms of the Bahama Archipelago are geo-
logically world famous as a natural laboratory for the study of the sedimentol-
ogy and paleontology of Quaternary carbonate rocks and sediments (see Curran
and White, 1995 on Bahamian terrestrial and shallow-marine geology, and
Ginsburg, 2001 on Bahamian carbonate platform evolution). Pleistocene and
Holocene rocks cap these islands, and their diverse modern carbonate sedimen-
tary environments contain a commonly diagnostic ichnological signature.
The purpose of this section is to provide a brief, informative overview of the
ichnology of the Bahamas; in-depth coverage can be found in Curran (1994,
2007) and references therein. A principal benefit gained from study of Baha-
mian ichnology is insight regarding the modern-to-fossil transition. Given that
rocks of the Bahama Islands are geologically young, in many cases one can
match modern tracemaker activity to analogs found in the fossil record. Trace
fossils discussed here all fall within either the Skolithos or the Psilonichnus
Ichnofacies that characterize the predominately grainstone lithofacies. Bioero-
sion is an important aspect in reef destruction and rocky-shore erosion and was
recently reviewed by Bergman et al. (2010) .
Modern carbonate environments and their counterpart units in the Bahamian
rock record range from shallow-subtidal, commonly reefal settings, to beach and
dune environments, as found along grainy, windward, or leeward island coasts.
More protected environments that might exist marginal to coastal embayments,
such as tidal flat-lagoon complexes, also are included. Figure 9 illustrates two
hypothetical Bahamian islands and the spatial distribution of these coastal envi-
ronments, with the side panel illustrating five ichnocoenoses recognized by
Curran (2007) , and each keyed to its respective depositional environment. In
addition, Garrett (1977) described several invertebrate communities (nearshore,
pond, and levee) fromthe extensive, mud-dominated tidal flats on thewest side of
Andros Island that could be regarded as a separate ichnocoenosis.
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