. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. \&\ TOPOGRAPHIC RIDGES INTERMITTENT STREAM CHANNEL Figure 10. Plan view of polygonal karst pattern on the surface of Miocene limestones, Papua, New Guinea (Purdy and Bertram, 1993; modified from Williams, 1972). Such honeycomb shoals are common features of shallow lagoon areas and have also been well documented in the Cocos (Keeling) Islands (Searle, 1994). Searle noted that the "central southeastern part of the lagoon is occupied by steep-sided 'blue holes,' some over 15 m deep" (p. 5), and 100
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. \&\ TOPOGRAPHIC RIDGES INTERMITTENT STREAM CHANNEL Figure 10. Plan view of polygonal karst pattern on the surface of Miocene limestones, Papua, New Guinea (Purdy and Bertram, 1993; modified from Williams, 1972). Such honeycomb shoals are common features of shallow lagoon areas and have also been well documented in the Cocos (Keeling) Islands (Searle, 1994). Searle noted that the "central southeastern part of the lagoon is occupied by steep-sided 'blue holes,' some over 15 m deep" (p. 5), and 100 m wide (Fig. 11). These, Searle suggested, are related to "multi-generational dolins" (p. 5), although he emphasized that both differential accretion and erosional relief are responsible for atoll lagoon Figure 11. Aerial view of southern area of Cocos (Keeling) Islands lagoon. Note honeycomb ridge pattern ( Searle, 1994). A core hole drilled in the Pelican Cays by the University of Miami in 1984 recovered Pleistocene limestone at a depth of about 20 m (R. N. Ginsburg, personal communication, 1994). This depth coincides with the depth at which our probe encountered hard rock on the outside of Pond C. It is therefore not unreasonable to assume that our probe was recording the Pleistocene. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution. Press; National Research Council (U. S. ). Pacific Science Board; Smithsonian Institution; National Museum of Natural History (U. S. ); United States. Bureau of Sport Fisheries and Wildlife. Washington, D. C. : [Smithsonian Press]
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