Bikini and nearby atolls. Part 1, geology

Emery, K. O.; Tracey, Joshua I.; Ladd, Harry S.

doi:10.3133/pp260a

Cited by 121 publications

(95 citation statements)

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“…Examination of the reef crests and flats at Takapoto and Tikehau Atolls (Bouchon 1983;Harmelin-Vivien 1985;Salvat and Richard 1985) and comparing their zonations to other Pacific atolls (Doty and Morrison 1954: Figs. 1-5;Emery et al 1954;Newell 1956) indicates that there is considerable variation in their geomorphology, turbulence and tidal ranges. These factors are strongly influenced by the frequency, duration, directions and wind velocities during storms, which may in turn influence the geomorphic zonations and the biological responses to them.…”

Section: Modern Coralgal Reefs Tuamotu Archipelagomentioning

confidence: 95%

Biologic response to environmental stress in tropical reefs: Lessons from modern Polynesian coralgal atolls and Middle Permian sponge and Shamovella-microbe reefs (Capitan Limestone USA)

Fagerstrom

Weidlich

2005

Facies

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Despite prejudices that comparisons of paleoecological patterns in modern and fossil reef communities are of doubtful validity, we compare the biologic response of living coralgal reefs in French Polynesia to environmental stress with an exceptionally well exposed Middle Permian sponge reef and Shamovella-microbial reef of the Capitan Limestone in New Mexico. In the western Tuamotu Archipelago, reef margins are characterized by depth-related changes of biodiversity. The subtidal basic reefbuilding community contains the highest diversity (23 coral and 6 calcareous algal species). With decreasing water depth and increasing environmental stress, diversity reaches a minimum of five taxa on the reef flat. The Capitan consists of two reef stages. Reefbuilders of the lowermost exposed part of Stage 1 formed a cement-rich sponge reef with 42 taxa (28 sponge species). Decreasing water depth along the reef face is accompanied by loss of five taxa, variations in the gross morphology of sponges and changes in framework architecture. Stage 2, dominated by Shamovella obscura, one bryozoan species and microbes, is sandwiched between two unconformities suggesting much shallower water and higher environmental stress. Despite differences in shelf profile and taxonomy, both the modern and Permian reefbuilders respond to increasing environmental stress with diversity impoverishment and dominance of binders.

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Section: Modern Coralgal Reefs Tuamotu Archipelagomentioning

confidence: 95%

Biologic response to environmental stress in tropical reefs: Lessons from modern Polynesian coralgal atolls and Middle Permian sponge and Shamovella-microbe reefs (Capitan Limestone USA)

Fagerstrom

Weidlich

2005

Facies

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“…Diagenetic studies on preQuaternary (Newell, 1955;Bathurst, 1958Bathurst, , 1959 carbonate rocks remained primarily descriptive. Contemporaneously, however, others began studies on Pleistocene and Recent sediments (Emery et al, 1954;Hling, 1954;Ginsburg, 1957), and soon pointed out the possible importance of early diagenetic changes. Friedman (1964) recognized that Pleistocene carbonates of Bermuda had been lithified subaerially.…”

Section: Early Diagenesis -Concise History Of Investiganonmentioning

confidence: 99%

Marine and meteoric diagenesis of submarine pleistocene carbonates from the Bermuda Carbonate Platform

Vollbrecht

1990

Carbonates Evaporites

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The tectonically stable Bermuda Carbonate Platform has undergone repeated emersions and submersions in the course of the Pleistocene sea-level changes. Shallow seismic reflection profiling and high-energy vibration coring gave access to Pleistocene carbonates that are presently situated below sea level. A study of their diagenesis was undertaken in order to document the changes occuring in various diagenetic environments, to check a, possible correlation between the state of diagenetic preservation and stratigraphic age, and to estimate the odds for a complete diagenetic imaging of a sediment's pore-water history. For the purpose of comparison, several samples from the modern Bermuda Islands were analysed as well.As indicated by their biogenic constituents, the submarine Pleistocene carbonates were chiefly composed of aragonite and high-Mg-calcite at the onset of diagenesis, whereas they now commonly appear as mixtures of aragonite and low-Mg-calcite. Marine cements (five kinds of high-Mgcalcite cement, three kinds of aragonite cement) are, as a rule, restricted to the intraparticle pore space. Meteoric influence inflicted neomorphism, cementation with low-Mg-calcite (several kinds of cement) and solution on the marine carbonates. These are characterized by patchy lithification, abundant preserved pore space and incomplete mineralogical stabilization. Furthermore, especially in lagoonal sediments, burrow or root structures have been preferentially cemented. Indicators of karst and calichification are common. High-Mg-calcite is usually the first mineral to disappear under meteoric influence; aragonite is more stable. Intensely altered carbonates consist entirely of low-Mg-calcite, whereas dolomite does not occur at all.Diagenetic indications of meteoric-phreatic alteration are generally uncommon, but support the idea of fresh-water lenses that are largely restricted to the proximity of the present islands. Most of the carbonates, however, have received their decisive diagenetic imprints in the meteoricvadose environment.The diagenetic record within the carbonates is incomplete. Only one pore-water change is recorded, from a marine to a meteoric environment. Undoubted post-meteoric marine cements are absent from the studied Pleistocene material except for some intensely Iithified littoral deposits on the present islands. Obviously, the diagenetic potential of the marine environment was too small to compete with the meteoric environment. Under these circumstances, a reconstruction of pore-water history based on diagenetic sequences is deceptive.

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“…A number of early authors produced maps showing the distribution of reefs world-wide (Darwin 1842;Joubin 1912;Emery et al 1954), but it was not until the 1970s that significant efforts were made towards the generation of estimates of global reef area (Table 1). Two broad approaches have been used in the generation of these estimates: one involves the direct calculation of reef area using existing reef maps (Newell 1971;De Vooys 1979); the other involves the calculation of reefal shelf area using more predictive techniques (Milliman 1974;Smith 1978;Copper 1994; Kleypas in press).…”

Section: Introductionmentioning

confidence: 99%