Lagoon Depth Research Articles

A Late Quaternary Record of Natural Change and Human Impact from Rangihoua Bay, Bay of Islands, Northern New Zealand

A multiproxy analysis of back-dune sediment cores from Rangihoua Bay, northern New Zealand, provides an environmental history of the Late Quaternary, placing human impacts on the site into a geomorphological and ecological context. The inferred paleoecological significance of the trends is generally coeval between proxies. The history commences with a Late Pleistocene deposit that formed part of a river terrace during lower sea level. The dryland vegetation at that time was dominated by Fuscospora forest. The record recommences at ca. 7400 YBP, by which time Fuscospora had been replaced by podocarp-hardwood forest, comprising mainly Dacrydium and Prumnopitys taxifolia emerging through a Metrosideros canopy. One of the core sites was a lagoon fringed with mainly Cyperaceae, Leptospermum, and Dodonaea. Redox-sensitive elements reflect phases of anoxia related to variation in lagoon depth. Transition from lagoon to peat swamp, due to natural infilling and/or climate change, occurred after ca. 5500 YBP. Human impacts were of high magnitude and include deforestation of the catchment and drainage of the wetland by early Polynesians. Errors in the radiocarbon and tephra chronologies preclude an accurate date for this. Microfossils of introduced Polynesian plants and a thick gravel bed in one of the cores suggest that parts of the wetland were used for prehistoric horticulture.

ANALYSIS OF ANISOTROPIC VARIOGRAM MODELS FOR PREDICTION OF THE CURONIAN LAGOON DATA

The anisotropy in particular environmental phenomena is detected when behavior of a physical process differs in different directions. In this paper geometric and zonal anisotropies are considered. Various methods of geostatistical analysis, also isotropic and geometrical anisotropic variogram models are compared and applied for the Curonian lagoon depth data. The results demonstrate that after robust estimation, i.e. elimination of outliers and after elimination of geometric anisotropy the precision of prediction and adequacy of models are much better. All computations have been performed by means of gstat, base and spatial packages of R system. Prediction results are compared with the results of research where outliers and geometric anisotropy were not eliminated.

Contradicting Barrier Reef relationships for Darwin’s Evolution of reef types

The Darwinian progressive subsidence model for the evolution of fringing reefs, barrier reefs and atolls has been generally accepted following the indisputable proof of subsidence provided by drilling results in the Pacific. Nonetheless, there are data that do not fit the expectations of the model, such as the similar lagoon depths of barrier reefs and atolls as opposed to the subsidence theory’s implicit prediction that atolls should have significantly greater depths. In contrast, a great deal of evidence supports the influence of meteoric solution on barrier reef morphology. For example, the maximum lagoon depth of 56 modern barrier reefs is statistically correlated with the lagoon catchment area for modern annual rainfall. These modern rainfall patterns would seem to be a reasonable proxy for relative geographic differences in glacial lowstand rainfall, even though the absolute amounts of such rainfall are unknown. The correlation therefore suggests the importance of Pleistocene subaerial solution in contributing to barrier reef morphology. Further support for antecedent influence occurs in the form of barrier reef passes in which the depth of the reef pass is correlated with onshore drainage volumes. On a larger scale, the Cook Island of Mangaia provides evidence that solution can produce barrier reef morphology independent of reef development. In contrast, there are no examples of the subsidence-predicted lagoon transition of fringing reefs to barrier reefs to atolls. Moreover, the common occurrence of fringing reefs within barrier reefs negates subsidence as a causal factor in their ‘presumed progressive evolutionary development. Consequently, the evidence to date suggests that a solution morphology template has been accentuated by reef construction to produce the diagnostic barrier reef morphology we see today. The importance of subsidence would seem to be in accounting for the overall thickness of the resulting carbonate caps of oceanic examples and in contributing to lagoon depth variation among the larger continental entities.

An evolutionary model for sabkha development on the north coast of the UAE

The north coast of the United Arab Emirates (UAE) provides a typical example of coastal sabkha (supratidal flat) formation. Various stages of sabkha development can be recognized along this coast. This paper combines previous studies of sabkha environment with the results of field investigation of sabkha geomorphology, sedimentology, and stratigraphy on the north coast of UAE, to formulate a model of sabkha evolution. The model has six stages in the evolution of coastal sabkhas following the early Holocene sea-level rise. These are: Stage 1: sea-level rise results in the formation of an embayment. Stage 2: involves subsequent spit development and progradation across the bay as a result of sediment availability. Stage 3: coincident with spit evolution is the development of a khor (tidal inlet) with or without mangrove. Channel depth of Khors varies from 4 to 6 m. Stage 4: sediment accumulates in the khor reducing the khor depth, turning it into a lagoon. There are three sub-stages of the lagoon stage. (a) With lagoon depths of 1–2 m, (b) with lagoon depths 0.5 m or less, (c) when the lagoon floor is exposed at low tide. Stage 5: is sabkha formation; development occurs in two sub-stages. In the first the sabkha is immature and flooded during rain storms and spring tides (0.1 m above present sea-level). Later the sabkha is only flooded after rainstorms, when it reaches an elevation of about 1 m or more above present sea-level. Stage 6: in sabkha development is the coastal plain, which results when large sabkhas are linked together.

Coral reef sedimentation on Rodrigues and the Western Indian Ocean and its impact on the carbon cycle

Coral reefs in the southwest Indian Ocean cover an area of ca. 18,530 km2 compared with a global reef area of nearly 300,000 km2. These regions are important as fishing grounds, tourist attractions and as a significant component of the global carbon cycle. The mass of calcium carbonate stored within Holocene neritic sediments is a number that we are only now beginning to quantify with any confidence, in stark contrast to the mass and sedimentation rates associated with pelagic calcium carbonate, which have been relatively well defined for decades. We report new data that demonstrate that the reefs at Rodrigues, like those at Reunion and Mauritius, only reached a mature state (reached sea level) by 2-3 ka: thousands of years later than most of the reefs in the Australasian region. Yet field observations show that the large lagoon at Rodrigues is already completely full of carbonate detritus (typical lagoon depth less than 1 m at low spring tide). The presence of aeolian dunes at Rodrigues indicates periodic exposure of past lagoons throughout the Pleistocene. The absence of elevated Pleistocene reef deposits on the island indicates that the island has not been uplifted. Most Holocene reefs are between 15 and 20 m in thickness and those in the southwest Indian Ocean appear to be consistent with this observation. We support the view that the CO2 flux associated with coral-reef growth acts as a climate change amplifier during deglaciation, adding CO2 to a warming world. southwest Indian Ocean reefs could have added 7-10% to this global flux during the Holocene.

Equations for designing tidally affected harbours and lagoons, and for calculating water exchange in coast‐connected lakes

A three-dimensional flow and transport model was used to simulate the flow of water and assumed conservative substance in a large number of hypothetical, sea-connected lagoons and harbours experiencing tidal effects. The dimensions of the lagoons and harbours were selected to cover a wide range of widths, lengths, depths and entrance channel widths. The tidal flow in and out of each lagoon and harbour was simulated for durnal and semidurnal conditions for different tidal ranges. The water exchange for each lagoon and harbour was assessed on the basis of the exchange coefficient. The results of model runs and non-linear multiple regression techniques were used to develop equations for calculating the average exchange, in terms of lagoon dimensions, depth and tidal range for durnal and semidurnal conditions. These equations can be used for a quick assessment of water exchange conditions in lagoons and harbours, upon which their water quality depends. In designing an artificial, sea-connected lagoon and harbour, the developed equations can be used in the preliminary stages for testing options regarding the number and widths of entrances and the physical layout of the lagoon and harbour. This approach also allows for identification of unsuitable options, with the acceptable options being subjected to detailed mathematical modelling to assess their expected water exchange and water quality. The same approach can be applied to existing lagoons (natural or artificial) and harbours in designing layout modifications for improving water exchange and water quality conditions, as well as lakes directly connected to coastal waters and subject to tidal effects. The use of the equations presented in this report also can provide knowledge regarding the preferred water flushing conditions and/or improvements needed to enhance the water exchange in order to preserve the ecosystems in such water systems.

APPROCHE EXPÉRIMENTALE POUR L'ÉTUDE DES DIATOMÉES DES SÉDIMENTS DE LA LAGUNE DE VENISE, ITALIE

Continued studies on diatoms living in the Venice lagoon southern basin sediments have investigated the essential role of the two variables, light and temperature, on their development or their survival capability. Part of the research consisted of transferring lagoon depth sediments to the laboratory, using of special sample-cases designed for this purpose of not disturbing the sediment. The collected material was subjected to different light and temperature conditions. The experimental samples were periodical core over a period of a week and compared with the initial values of samples drawn “in situ”. The results confirmed the constant increase of cells on the sediment surface. The highest increase occurred when the phototactical stimulus was induced by lower luminous intensities, despite the fact that moisture was limited but most likely compensated for by the sediment composition (thin sands of clayey type), which appears to have had a satisfactory water retention. This suggests that the location of these organisms inside the sedimentary matrix is the compromise between water requirements and energy demands (as diatoms that can change feeding system, from autotrophic to heterotrophic). The exposure period (continuous light or alternation of light and dark) doesn't seem to affect the population increase. Some diatom strains have been isolated from the collected material. In particular, growth tests with different luminous intensities and temperatures have been performed on a strain belonging to the Navicula genus. Apart from the available quantity of light, the results of these tests emphasize that exponential phase is reached in a shorter period of time in strains maintained at higher temperatures. The influence of luminous intensity has proved to be less significant.

LIQUID BALANCE MODEL FOR SWINE WASTE MANAGEMENT SYSTEMS USING SINGLE–STAGE ANAEROBIC LAGOONS

The most important wastewater operation for farmers using lagoons to treat swine waste is maintaining the liquidlevel within the operational levels to avoid overflows and to satisfy the water demand for irrigation. This study describes amodel developed to determine liquid levels of singlestage anaerobic lagoons. Using this model, swine producers candetermine the best liquid handling for their operations. Inputs required are lagoon dimensions; hog numbers, sizes, sex, andplace in breeding cycle; records of management decisions; and accurate measurements of temperature, precipitation,humidity, wind speed, and solar radiation. The model was calibrated and validated for three singlestage lagoons in differentclimatic regions within the state of Oklahoma. Simulation results indicate that the model predicted liquid level within 3% of the observed values.<br><br>Determining evaporation proved to be the most critical component of the water balance for lagoons. Evaporation wasfound to follow the modified Penman equation. A linear equation to relate net radiation to solar radiation was found to besufficiently accurate to estimate evaporation from the lagoons used in calibration and validation. A single set of evaporationcoefficients accurately predicted lagoon evaporation for the examined set climatic regions, lagoon depths, and lagoon colors.<br><br>Sensitivity of the model to errors in nine input parameters was determined for two sites by simulating model performanceover a oneyear period. If accurate estimates of farm water use are available, then the model is most sensitive to errors inestimating precipitation and evaporation. Solar radiation proved to be the most sensitive single parameter for estimating surface evaporation.

Origin of atoll lagoons

Research Article| July 01, 2001 Origin of atoll lagoons Edward G. Purdy; Edward G. Purdy 1PetroQuest International Inc., “Foxbourne,” Hamm Court, Weybridge, Surrey KT13 8YA, UK Search for other works by this author on: GSW Google Scholar Edward L. Winterer Edward L. Winterer 2Scripps Institution of Oceanography, La Jolla, California 92093, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Edward G. Purdy 1PetroQuest International Inc., “Foxbourne,” Hamm Court, Weybridge, Surrey KT13 8YA, UK Edward L. Winterer 2Scripps Institution of Oceanography, La Jolla, California 92093, USA Publisher: Geological Society of America Received: 09 Nov 1999 Revision Received: 04 Aug 2000 Accepted: 12 Aug 2000 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2001) 113 (7): 837–854. https://doi.org/10.1130/0016-7606(2001)113<0837:OOAL>2.0.CO;2 Article history Received: 09 Nov 1999 Revision Received: 04 Aug 2000 Accepted: 12 Aug 2000 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Edward G. Purdy, Edward L. Winterer; Origin of atoll lagoons. GSA Bulletin 2001;; 113 (7): 837–854. doi: https://doi.org/10.1130/0016-7606(2001)113<0837:OOAL>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A database of 301 atolls from the Pacific, Indian, and Atlantic Oceans has been analyzed with respect to factors governing maximum atoll lagoon depth. Statistically significant correlations between maximum atoll lagoon depth and both atoll area and present-day rainfall are viewed as the combined effect of paleorainfall precipitation and catchment area in contributing to overall atoll morphology.This interpretation is supported by the gross saucer-shaped morphology of several of the Lau group of the Fiji Islands, and the subsurface Cretaceous Golden Lane atoll of Mexico, where evidence of reef rim construction is lacking but evidence for significant solution relief is compelling. The contribution of reefs to atoll rim construction appears to be limited generally to ∼10 m, leaving more than 20 m of relief to be explained at most atolls. At a number of these, the last interglacial highstand surface is ∼15−20 m beneath Holocene rim sediments. Subsidence rates of even 5 cm/ k.y. do not suffice to explain the subsea depth of this unconformity, suggesting the dominating influence of solution on relief expression.Calculations of solution rates relative to the residence time of sea level below given depths during the past 700 k.y. suggest that the observed atoll relief is in part inherited from more than one Pleistocene, or perhaps earlier, glacial stage. Whatever the precise time of origin, the data available strongly suggest that atoll morphology is solution determined rather than growth predicated. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Holocene development of three isolated carbonate platforms, Belize, Central America

Locally operating factors such as topography of the reef basement and exposure to waves and currents rather than regionally effective factors such as the post-glacial sea level rise in the western Atlantic explain the different Holocene developments of the three isolated carbonate platforms Glovers Reef, Lighthouse Reef, and Turneffe Islands offshore Belize. A series of NNE-striking tilted fault-blocks at the passive continental margin forms the deep basement of the Belize reefs. Glovers and Lighthouse Reefs are located on the same fault-block, while Turneffe Islands is situated west of Lighthouse Reef on an adjacent fault-block. The three platforms are surrounded by deep water and have surfacebreaking reef rims. Significant differences exist between platform interiors. Glovers Reef has only 0.2% of land and an 18 m deep, well-circulated lagoon with over 800 patch reefs. Lighthouse Reef has 3% of land and a well-circulated lagoon area. Patch reefs are aligned along a NNE-striking trend that separates a shallow western (3 m) and a deeper eastern (8 m) lagoon. Turneffe Islands has 22% of land that is mainly red mangrove. Interior lagoons are up to 8 m deep and most have restricted circulation and no patch reefs. Surface sediments are rich in organic matter. In contrast, the northernmost part of Turneffe Islands has no extensive mangrove development and the well-circulated lagoon area has abundant patch reefs. Holocene reef development was investigated by means of 9 rotary core holes that all reached Pleistocene reef limestones, and by radiometric dating of corals. Maximal Holocene reef thickness reaches 11.7 m on Glovers Reef, 7.9 m on Lighthouse Reef, and 3.8 m on Turneffe Islands. Factors that controlled Holocene reef development include the following. (1) Holocene sea level. The margin of Glovers Reef was flooded by the rising Holocene sea ca. 7500 YBP, that of Lighthouse Reef ca. 6500 YBP, and that of Turneffe Islands between 5400 and 4750 YBP. All investigated Holocene reefs belong to the keep-up type, even though the three platforms were flooded successively and, hence, the reefs had to keep pace with different rates of sea level rise. (2) Pre-Holocene topography. Pleistocene elevation and relief are different on the three platforms. This is the consequence of both tectonics and karst. Different elevations caused successive reef initiation and they also resulted in differences in lagoon depths. Variations in Pleistocene topography also explain the different facies distribution patterns on the windward platforms that are located on the same fault-block. On Lighthouse Reef tectonic structures are clearly visible such as the linear patch reef trend that is aligned along a Pleistocene fault. On Glovers Reef only short linear trends of patch reefs can be detected because the Pleistocene tectonic structures are presumably masked by the higher Holocene thickness. The lower Pleistocene elevation on Glovers Reef is probably a consequence of both a southward tectonic tilt, and stronger karstification towards the south related to higher rainfall. (3) Exposure to waves and currents. Glovers Reef, Lighthouse Reef, and the northernmost part of Turneffe Islands receive the maximum wave force as they are open to the Caribbean Sea. Adjacent lagoons are well-circulated and have luxuriant patch reef growth and no extensive mangrove development. By contrast, most of Turneffe Islands is protected from the open Caribbean Sea by Lighthouse Reef to the east and is only exposed to reduced wave forces, allowing extensive mangrove growth in these protected areas.

The Stratified Facultative Lagoon for the Treatment and Storage of High Strength Agricultural Wastewaters

A research and development programme at The University of New South Wales and a large intensive piggery located on the outskirts of Sydney, Australia, has culminated in the successful commissioning of an odour control process for the storage and treatment of wastewaters from the piggery. The stratified facultative lagoon utilises surface aeration of an otherwise anaerobic lagoon to provide a non-odorous cover for the anaerobic contents. The process has filled a need in the pig industry for a non-odorous cost effective alternative to conventional treatment systems, prior to wastewater re-use or disposal by land application. Critical design parameters include lagoon depth, specific energy input and aeration system design. Mean removal efficiencies of biochemical oxygen demand of 75 per cent have been achieved consistently. The development of the process was facilitated by the use of wastewater redox potential testing to indicate the likely presence of odorous compounds in the liquid on the surface of the lagoon and in the surrounding atmosphere. Surface redox potential readings (Eh) greater than −76 mV resulted in non-odorous operation of the process.

Nest Site Selection by the Exotic Chestnut Mannikin (Lonchura malacca) in Puerto Rico

Chestnut mannikin (Lonchura malacca), an Estrildine finch recently introduced in Puerto Rico, is a widespread Southeast Asian species. In its native habitat it frequently nests in vegetation over water, but in Puerto Rico it usually nests in dense sugar cane. In a marsh ecosystem in Humacao, mannikins nest in clumps of Cyperus spp. growing on top of stumps in a lagoon (depth = 50 cm). Their nests are in sedge clumps that are in shallower water and on higher stumps, and that are taller, wider and denser than clumps without mannikin nests. Nests were usually placed on the south side of the clump, with the entrance facing open water. The predator protection offered by nesting over water may account for nests being placed in relatively open sites. SPECIES THAT EXPAND THEIR BREEDING RANGE, with or without human assistance, into new geographical areas may expand their nesting sites either by nesting in entirely new habitats (i.e., moving from forests to fields), by nesting in different sites within preferred habitats, or both. Presumably constraints from predation pressures, nest site competition, and environmental factors shape nest site choices in the newly-colonized breeding range. In this paper we examine nest site selection in a population of chestnut mannikin (or munias Lonchura malacca) in a marsh in Puerto Rico. Factors affecting nest site selection include social and physiognomic features of the environment (Burger 1985). Social factors include attraction to conspecifics that provide antipredator or information transfer advantages (Fuchs 1977, Nuechterlein 1981, Burger 1981), or avoidance of other species because of predation (Greig-Smith 1982). Physiognomic aspects of nest site selection include factors such as structural stability (Coon et al. 1981), foliage density (Furrer 1980), vegetation height (Cody 1985), orientation relative to the sun (Reynolds & Knapton 1984), and perch site availability (Gochfeld 1979). Some species appear to have very strict nest site requirements or preferences, whereas others tolerate a wide variety of sites. The chestnut mannikin, munia, or black-headed nun is one of several recently introduced Estrildine finches which has become common in Puerto Rico (Raffaele 1983). It naturally ranges from India through southern China and Southeast Asia to the Philippines and Indonesia (Delacour & Mayr 1946, Smythies 1960, Long 1981, Ali & Ripley 1983). The recentness of its establishment in Puerto Rico is reflected by the fact that Long (1981) did not include it in his compendium of feral exotic bird species. The genus Lonchura is a popular cagebird, and eight species within the genus have successfully established feral populations in regions remote from its natural range (Long 1981). This suggests that the genus is either adaptable with respect to habitat selection, or cosmopolitan with respect to habitat requirement. We wished to examine qualitatively whether chestnut mannikin in Puerto Rico used habitats similar in physiognomy to those in its native habitat, and examine quantitatively whether its choice of nest sites differed from the available habitat. Our general approach to nest site selection is to contrast nest sites with sites that are available but not used (Burger & Gochfeld 1985). We interpret these findings in the light of Skutch's (1976) concept that nest sites should be invisible, inaccessible, impregnable. STUDY AREA AND METHODS We studied chestnut mannikin in Frontera Palmas Lagoon of the Humacao Rufuge (operated by the Puerto Rico Departamento de Recursos Naturales) in June 1987 and February 1988. The Humacao Refuge contains 600 ha of brackish coastal marshes created by hurricanes in the late 1970's, and presently maintained by dikes and management. The palmas lagoon once supported a coconut palm plantation (Cocos nuciferos), but as the trees have died since the flooding, the rotting stumps support a growth of grasses (e.g., Paspalum spp.), Cyperus sedges, and ferns. Small stumps often had no vegetation, whereas wide stumps usually had one dominant plant. ' Received I I April 1988, revision accepted 24 August 1988. 364 BIOTROPICA 21(4): 364-368 1989 This content downloaded from 157.55.39.46 on Mon, 13 Jun 2016 05:24:06 UTC All use subject to http://about.jstor.org/terms

CORAL REEFS IN THE GILBERT, MARSHALL, AND CAROLINE ISLANDS

Research Article| August 01, 1946 CORAL REEFS IN THE GILBERT, MARSHALL, AND CAROLINE ISLANDS L. E NUGENT, JR. L. E NUGENT, JR. P. O. BOX 1720, FORT WORTH, TEXAS. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1946) 57 (8): 735–780. https://doi.org/10.1130/0016-7606(1946)57[735:CRITGM]2.0.CO;2 Article history received: 19 Sep 1945 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation L. E NUGENT; CORAL REEFS IN THE GILBERT, MARSHALL, AND CAROLINE ISLANDS. GSA Bulletin 1946;; 57 (8): 735–780. doi: https://doi.org/10.1130/0016-7606(1946)57[735:CRITGM]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The 77 atolls, 35 banks, 21 lagoonless coral islands, 5 reef-encircled volcanic islands, and 2 raised “phosphate” islands in the Gilbert, Marshall, and Caroline groups extend from 132° to 177° East Long, and from 15° North to 3° South Lat. The seamounts are located on three types of submarine trends: The Gilberts, Ralik and Radak chains of the Marshalls, and eastern Carolines lie on gently arcuate trends with each member perched as an individual; the west-central Carolines evidence no regional alignment or arrangement but lie on a broad rise 1000 fathoms high; Yap and Palau are small island arcs. The submarine slopes of the seamounts average from 25° to 35° for the upper 1000 fathoms.The Gilbert atolls are abnormally shallow and manifest slight regional tilting and excessive variation of reef width from windward to leeward. Aranuka has a bank at lagoon depth that extends several miles beyond the western reef margin.The Marshall atolls exhibit remarkably uniform reef widths and lagoon depths. Kwajalein has a lagoon area of 663 square miles. Aur is tilted to the south and evidences no detrital filling or leveling; Eniwetok has a current that affects only one fourth the lagoon, yet it is the same depth throughout.In the Carolines, Zohhoiiyoru, Kapingamarangi, Oroluk, Nomwin, and Murilo have abnormal lagoon floors that condemn detrital leveling; Ngatik, 87 fathoms, and Nukuoro, a “two-story” atoll, in turn condemn detrital filling. In the west-central Carolines none of the banks lie under more than 50 fathoms, and Gray Feather and Mogami, the two largest, are separated by a narrow shallow passage with rim reef growth on each side, evidence incompatible with the sheath-like coral growth that should accompany major subsidence. The reef-encircled volcanic islands have truncated spurs and cliffed shorelines; reef widths and lagoon floors are normal.The accordance of lagoon and bank depths, the uniformity of reef width, the absence of inboard detrital slopes, pass notches, and outboard deltas, the general absence of coral causeways or piers, the angularity of shape, the demonstrated inefficacy of detrital filling and leveling, and the presence of truncated spurs and cliffed shore lines all indicate seamount truncation during the Pleistocene. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.