Western Pacific Islands Research Articles

Exploration Indices and Mineral Potential Map of the Kuroko Deposits in Northeast Japan

Abstract. Recent discoveries of seafloor hydrothermal mineralization in submarine volcanic centers of felsic magma in western Pacific island arcs are regarded as modern analogues of Kuroko type deposits. Studies of these deposits and their surrounding geology raised question whether the exploration activity for the Kuroko deposits on land which peaked in the 1960's was adequate or not. However, such an evaluation is not easy because the exploration data are about to be lost as a result of the closure of all the Kuroko mines in the area since 1994.The Metal Mining Agency of Japan (MMAJ), therefore, decided to compile existing data on about 180 Kuroko deposits and related mineral occurrences in northeast Japan as a new Kuroko database.This study extends a concept called “exploration indices” which was developed based on a case study of the thoroughly surveyed Hokuroku district to draw a potential map of the Kuroko occurrences for the entire northeast Japan quantitatively with a Geographical Information System (GIS). Effective exploration indices include: 1) distribution of dacitic‐rhy‐olitic submarine volcanic rocks of the Nishikurosawa and Onnagawa stages, 2) distribution of intrusive rocks of pre‐ and post‐Kuroko horizon, 3) low aeromagnetic anomaly caused by hydrothermal alteration of magnetite, 4) low gravity anomaly which suggests depressions in the basement rocks such as a tectonic basin and/or caldera, and 5) nearby existence of vein type deposits. It is concluded that about 33 % of known Kuroko deposits fall within the high potential zone (score=4 and 5) that occupies only 4 % of the entire northeast Japan arc. The Kuroko potential map is, therefore, useful for limiting the target area for Kuroko type deposits in an island arc setting.

Variation of Cl and SO3 Contents of Microphenocrystic Apatite in Intermediate to Silicic Igneous Rocks of Cenozoic Japanese Island Arcs: Implications for Porphyry Cu Metallogenesis in the Western Pacific Island Arcs

Abstract. Determinations of SO3 and Cl contents of igneous accessory apatite were carried out on Late Cenozoic intermediate to silicic intrusive and volcanic rocks in the Japanese island arcs of the western Pacific rim including the southwestern Kuril arc (eastern Hokkaido), Northeast Japan arc (southwestern Hokkaido through northeastern Honshu to central Honshu), Izu‐Bonin arc, Kyushu‐Palau ridge, Southwest Japan arc (northern Kyushu) and northern Ryukyu arc (southern Kyushu). These were compared to those from the Western Luzon arc, Philippines, to better understand the metallogenesis of porphyry Cu deposits in the western Pacific island arcs. In addition, SO3 and Cl contents of accessory apatite in the Cretaceous magnetite‐series granitic rocks in the Kitakami belt (northeastern Honshu) and the Miocene ilmenite‐series granitic rocks in the Outer Zone of Southwest Japan (southern Kyushu) were also examined.Microphenocrystic apatites in shallow intrusions associated with porphyry Cu deposits in the Western Luzon arc contain >0.1 wt% S as SO3. Such high SO3 contents of microphenocrystic apatite are a common characteristic of hydrous mag‐matism in the Western Luzon arc, from 15 Ma old tonalitic plutonic rocks of the Luzon Central Cordillera to present‐day volcanism at Mount Pinatubo. The accessory apatite in intrusive rocks associated with porphyry Cu deposits, especially those at the Santo Tomas II deposit, show significantly high Cl contents (>2 wt%).The SO3 contents of microphenocrystic apatite in most of the hydrous silicic rocks along the volcanic front, in andesites related to native sulfur deposits, and in Miocene and younger shallow granitic intrusions in northeastern Honshu, are generally <0.1 wt%. On the other hand, the SO3 contents of apatite in such rocks from eastern Hokkaido, southwestern Hokkaido, Izu, northern Kyushu and southern Kyushu are similar to those from the Western Luzon arc. The SO3 contents of accessory apatite in the Cretaceous magnetite‐series granitic rocks in the Kitakami belt are variable, whereas those of the Miocene ilmenite‐series granitic rocks in southern Kyushu are extremely low. The Cl contents of accessory apatite in some rocks of the Northeast Japan arc, Izu‐Bonin arc and Southwest Japan arc are significantly high.In terms of the Cl and SO3 contents of microphenocrystic apatite, Cenozoic Japanese arc magmatism show similarities with arc magmatism associated elsewhere with porphyry Cu mineralization, except for the most of northeastern Honshu of the Northeast Japan arc. Apatite commonly occurs as inclusions in other phenocrystic phases. Thus the variation in SO3 contents of apatite is a feature of early stage magmatic differentiation. The SO3 contents of microphenocrystic apatite are considered to reflect the redox state of the magma source region or fluids encountered during magma generation.

The Archaeology of Lapita Dispersal in Oceania: Papers from the Fourth Lapita Conference, June 2000, Canberra, Australia (review)

Reviewed by: The Archaeology of Lapita Dispersal in Oceania: Papers from the Fourth Lapita Conference, June 2000, Canberra, Australia Jim Specht The Archaeology of Lapita Dispersal in Oceania: Papers from the Fourth Lapita Conference, June 2000, Canberra, Australia. Edited by G. R. Clark, A. J. Anderson, and T. Vunidilo. Terra Australis 17. Canberra: Pandanus Book, Australian National University, 2001. viii + 222 pp. ISBN 1-74076-010-7. Since the Lapita Homeland Project (LHP) in the Bismarck Archipelago in 1985, there has been a string of conferences relating to Lapita pottery, its predecessors and successors. Originally, the conferences were designed as a forum for reporting on the outcomes of the LHP, but from 1988 the format was broadened beyond this narrow geographic focus, and now covers the western Pacific Islands from New Guinea to New Caledonia and Fiji-Tonga. The temporal boundaries are also broader than the few hundred years of the span of Lapita pottery. The 2000 conference was originally planned to take place in Fiji, but the venue [End Page 175] was relocated to Canberra following the Fijian coup attempt, just two weeks before the start of the conference. This relocation had several impacts on the conference, not least the reduction in non-Australasian participation, as many North American and other colleagues were unable to rearrange at the last minute their schedules and itineraries to accommodate the additional travel. This meant the absence of a number of significant 'players' in the region's archaeology, and a reduction in the overall scope of the conference papers. The resulting volume, however, is a significant one in its own right. The volume contains 19 of the 40 or so papers presented, covering a wide range of topics, places, and periods, though the period prior to Lapita is dealt with only in general terms in some papers. Geographically, the papers cover the Bismarcks (Summerhayes on Lapita chronology in the Arawe and Feni Island groups; Parr et al. on phytoliths and landscape-subsistence reconstruction on Garua Island; Leavesley on New Hanover earth mounds of uncertain age; Smith on Arawe shell artifacts; Torrence and White on Lapita faces from Boduna Island), Solomon Islands (Felgate on the Roviana pottery sequence), Vanuatu (Bedford on Malakula pottery; Spriggs and Bedford on possible Lapita at Mangaasi; Bedford and Clark on incised and relief pottery of Vanuatu and Fiji), New Caledonia (Sand on nonceramic artifacts), and Fiji (Parke on Vanua Levu pottery handles; Szabo on Natunuku molluscs; Valentin et al. on a late "prehistoric" burial mound on Cikobia). Less geographically focused are papers by Anderson and others on an inventory of Lapita sites, Anderson on Lapita mobility models, Davidson and Leach on "strandloopers" and naïve interpretation of subsistence data, Hagelberg on genetic affinities, Cameron on textile technology, and Bulmer on dogs in the New Guinea region. With such a diversity of topics, this review can only attempt a selective coverage, though all papers warrant reading. There is a strong representation of the younger generation of Pacific archaeologists. As the editors note, the papers "suggest that there are changing interests in Lapita and its descendant assemblages," and among these changes is an increasing focus on regional sequences and histories. The extent to which this is possible for any one area depends on the quality as well as quantity of available data, and the kinds of questions and theoretical frameworks within which these data can be articulated. Felgate's paper on Roviana illustrates this nicely. Following the remarkable results from Kirch's work on Eloaua and Gosden in the Arawes, the Roviana project focused explicitly on intertidal contexts to address the simple but significant question whether the lack of evidence for Lapita in the main Solomons' chain reflects lack of field research or Lapita "avoidance" of the region. This oversimplifies his argument, but the preliminary results provide sufficient evidence to instill caution against generalizing across the region. Sand's approach to the nonceramic artifacts of New Caledonia warns us to be wary of accepting perceptions based on data derived from a few points on the landscape. The range of nonceramic items is impressive, as are the changes through time suggested by his "seriation table" (p. 87). This invites comparison with Smith...

Pelagic fisheries catching blue and striped marlins in the US Western Pacific islands

Various pelagic fisheries in the US Western Pacific islands capture blue and striped marlins. Total catches by US vessels in the Western Pacific islands amount to about 2000 t for blue marlin and 600 t for striped marlin, or 9% and 5% of the nominal total Pacific-wide catch of these two species, respectively. Catch records for domestic Western Pacific fisheries typically extend over several decades, although in this short communication they are confined to blue and striped marlin catches in the 1990s. There are currently no specific management measures for marlins in the US Western Pacific islands, but other management measures for US pelagic fisheries in this region may have an influence on marlin catches.

New rates of western Pacific island arc magmatism from seismic and gravity data

Numerous studies have been conducted in order to look into the evolution of the continental crust. Some suggest that one of the mechanisms which contribute to the growth of continental crust is arc magmatism. It is in this context that Reymer and Schubert (Tectonics 3 (1984) 63) estimated arc magmatic addition rates to the continental crust. Their results suggest that island arc magmatism was producing material at an average rate of 20–40 km 3/km/Myr (volume per unit width along the strike direction of arc). The present work utilizes the most recent worldwide marine gravity data, together with improved seismic data from some oceanic island arcs in the western Pacific region. The combined gravity and seismic data allow a more accurate image of the subsurface configuration beneath the oceanic island arcs and yield better estimates of crustal volumes created during arc magmatic processes. Oceanic island arcs investigated in this study show a crustal thickness ranging from 20 to 30 km. Utilizing this thickness, the relevant crustal volume for each island arc is then estimated. Dividing the crustal volume by the age of initiation of subduction of the arc gives arc magmatic addition rates of 30–95 km 3/km/Myr. The estimates presented here are nearly twice as high as the previous estimates of arc magmatic addition rates.

Epidemiology of hepatocellular carcinoma

Because of its high incidence in many of the most populous countries in the world, its often fulminant course, poor response to conservative treatment, low resectabilty rate when symptomatic, high recurrence rate after resection and liver transplantation, and grave prognosis, hepatocellular carcinoma is now regarded as one of the major malignant diseases. Hepatocellular carcinoma is the most common primary malignant tumour of the liver. Relative to other tumours, it ranks fifth in overall frequency (fifth in men and eighth in women) and fourth in annual mortality rate. An estimated 372 000 new cases of hepatocellular carcinoma are diagnosed each year, constituting 4.6% of all new human cancers (6.3% in men; 2.7% in women). The annual mortality rate from the tumour is virtually the same as its annual incidence. The highest incidences occur in eastern and southeastern Asia, some of the Western Pacific islands, and sub-Saharan Africa. Intermediate incidences are found in eastern and southern Europe, the Caribbean, Central America, and Western Asia. Hepatocellular carcinoma is uncommon in the remaining countries. Men are affected more often than are women. The incidence generally increases with increasing age, although there is a definite shift towards a younger age distribution in black African and ethnic Chinese populations.

If I Give You My Child, Aren't We Family?

ABSTRACT While poverty is suspected to be the major reason for birth families relinquishing their children for international adoptions, little is known of the impact of the interplay among the economic, familial, and cultural aspects of a particular sending country which culminates in the adoption decision. In this study, the authors studied 73 birthmothers in the Republic of Marshall Islands, a small Western Pacific island nation with a total population of 68,000, to explore the influences that led to their adoption decision. Their findings reflect an environment of extreme poverty, the breakdown of traditional family support systems, and the exploitation of the cultural understanding of adoptions.

Medical advice for international travelers.

Each year, approximately 30 to 40 million Americans travel outside the United States. Although the most popular destinations are Europe, Central America, and the Caribbean, travel to Africa and Asia is increasing substantially. International travel, particularly to developing countries, can be associated with the risk of infectious and noninfectious diseases. These risks can be decreased, eliminated, or modified with vaccinations, prophylactic medications, and education. Optimally, pretravel advice must be individualized to a person's medical history, itinerary, and risk behavior. In addition to risk assessment-based immunizations, issues such as traveler's diarrhea, malaria prophylaxis, sexually transmitted diseases, and management of underlying medical problems must form a part of pretravel management. Adventure or prolonged travel or persons with underlying medical diseases such as insulin-dependent diabetes mellitus, transplantation, immunodeficiencies, and dialysis warrant additional preventive measures. This review primarily updates pretravel management of adults.

Parioglossus (Teleostei: Gobioidei: Microdesmidae) in New Zealand

The genus Parioglossus is known widely across the Indo‐West Pacific from tropical western Pacific islands (Fiji, Vanuatu, New Caledonia), through eastern subtropical to tropical Australia, in south‐east Asia and north to Japan, and west across the Indian Ocean to Madagascar. It is hitherto not recorded from New Zealand, but is here reported from a stream near North Cape in far northern New Zealand, and another draining a wetland on Great Barrier Island in the north‐east of the country. New Zealand specimens do not conform completely to any published descriptions of Parioglossus, but this seems likely to reflect inadequacies in the published descriptions. The fish appear closest to the eastern Australian P. marginalis. Typical habitat is unclear, though simple testing of euryhalinity suggests an ability to inhabit marine, brackish, and possibly fresh waters. Whether the species has been long present in New Zealand waters, undiscovered, has dispersed to New Zealand across the Tasman Sea in ocean currents, or was brought to New Zealand in ballast water discharged from ships, is not known. Parioglossus is one of several species newly discovered in New Zealand waters, for which various explanations are possible.

Collision tectonics in the New Hebrides arc (Vanuatu)

Abstract The New Hebrides island arc in Vanuatu has been significantly modified by collision with several major submarine ridges and plateaux. Bathymetric sections taken at intervals along the arc, perpendicular to the trench, show that prior to collision at 3 Ma the morphology was typical of modern intraoceanic island arcs. Collision has caused uplift of the trench and forearc (up to 6000 m), subsidence around the arc volcanic edifices (up to 2500 m), forming a large intra‐arc basin and uplift of the arc‐backarc transition (up to 2000 m). In the transition zone between collisional and non‐collisional sections of the arc, subsidence occurs in the forearc and uplift occurs around the arc volcanoes. Many of these characteristics are typical of collisions in other Western Pacific island arcs such as the Tonga–Kermadec and Izu–Bonin arcs. The pattern of uplift and subsidence has important implications for the tectonic history of the New Hebrides system. The morphology of the arc shows that collision of the West Torres Massif probably accounts for at least half the uplift. Arrival at 0.7 Ma of the West Torres Massif in the trench may have caused the slowing of subduction in the entire northern half of the arc and not just in the central segment as previously suggested. Re‐equilibration of the arc following collision probably masks any evidence of collision prior to 3 Ma. For example, the Efate re‐entrant, a large indentation in the arc immediately to the south of the collision zone, probably originated as a result of erosion during collision followed by subsidence after collision. The Vanuatu collision shows that the subduction of seamounts and ridges in an intraoceanic arc temporarily changes the arc morphology, allowing the development of angular unconformities and changing the pattern of sedimentation. This provides information which can be used to facilitate recognition of these events in ancient arc‐related sequences.

Factors Affecting the Distribution of Atyid Shrimps in Two Tropical Insular Rivers

Factors Affecting the Distribution of Atyid Shrimps in Two Tropical Insular Rivers Trina Leberer and Stephen G. Nelson Abstract We investigated factors affecting distribution of atyid shrimps, common inhabitants of insular freshwater ecosystems. Several abiotic and biotic variables were measured to determine their influence on atyid shrimp densities in two streams on the western Pacific island of Guam. Randomly selected sites, composed of three habitat types (riffles, runs, and pools), were surveyed in the rainy and dry seasons. We made visual counts of instream fauna in 2-m2 quadrats within each site. Various statistical analyses suggested that habitat type is a major factor affecting atyid distribution on Guam. However, results of a transplant experiment, conducted to test the effect of predators on atyid distribution directly, were noteworthy: no atyids remained in pools containing the transplanted jungle perch Kuhlia rupestris in the field. Our data indicate that both environmental factors and faunal interactions may be important influences on atyid distribution. Atyid shrimps are common in the freshwater habitats of oceanic islands. There are seven recorded species of stream atyids on the western Pacific island of Guam: Atyoida pilipes (Newport, 1847), Atyopsis spinipes (Newport, 1847), Caridina longirostris (Milne-Edwards, 1837), Caridina nilotica (Roux, 1833), Caridina serratirostris de Man, 1892, Caridina typus Milne-Edwards, 1837, and Caridina weberi de Man, 1892. All except Atyopsis spinipes were seen during this study. Caridina longirostris and C. weberi are new records for Guam (this study). All of these species are native to Guam, but none is endemic. Like most other atyids (Shokita 1976, Benzie 1982), all those occurring in the rivers of Guam are amphidromous, with their larvae drifting downstream to the ocean, developing in the plankton, and migrating back upstream as juveniles. Although some previous studies have addressed the postlarval ecology of atyids in various geographical locations (Hart 1981, Carpenter 1983, Dudgeon 1985, de Silva 1988, Crowl and Covich 1994), less information is available from the tropical Pacific Region. Couret (1976) provided a comprehensive summary of the biology of the Hawaiian atyid Atyoida bisulcata Randall, 1840, including aspects of its ecology. Bright (1979) included some ecological information in his study of freshwater ecosystems in Palau. Ellis-Neill (1987) concluded that current velocity and a greater abundance of leaf litter are important influences of invertebrate distribution (including atyids) on Guam. The ecology of atyids on Yap was briefly mentioned in Bright (1989). In this study, we addressed the following question: Which environmental and faunal factors affect the distribution of atyids on Guam? We analyzed several abiotic and biotic variables, including season, reach, habitat, pH, water temperature, maximum depth, canopy cover, substrate composition, abundance of aquatic vegetation, current velocity, and densities of other riverine fauna. Preliminary observations suggested that predation was an important faunal factor influencing atyid distribution. We examined predation in [End Page 389] two ways. First, we compared densities of atyid species with potential predator densities in a correlation analysis. In the streams of Guam, potential predators include the jungle perch Kuhlia rupestris (Lacépède, 1802); the freshwater eel Anguilla marmorata Quoy & Gaimard, 1824; the sleeper goby Eleotris fusca (Bloch & Schneider, 1801); the Mariana goby Awaous guamensis (Cuvier & Valenciennes, 1837); and the Tahitian prawn Macrohrachium lar (Fabricius, 1798). Stomach contents of these species (except M. lar) have been found to contain atyids (R. B. Tibbatts, pers. comm.). Second, to test the effect of predators on atyid distribution directly, we conducted a transplant experiment in the field, involving K. rupestris. Kuhlia are free-swimming, visual predators, occurring only in the lower reaches of rivers, below barrier waterfalls. If predation by Kuhlia is an important influence on the distribution of atyids in the streams of Guam, then densities of atyid species would be expected to be lower in pools containing transplanted K. rupestris than in control pools containing no K rupestris. Materials And Methods Study Area We collected data from two rivers (Figure 1). The Asmafines River (coordinates at the mouth: lat. 13° 19' 37" N, long. 144° 39' 03" E) is a high-gradient stream located in the south on Guam's steeper western slope, with a perennial channel length of 1341 m and an elevation of 134 m at the headwaters (Best and...

Geochemistry and isotopic composition of the Guerrero Terrane (western Mexico): implications for the tectono-magmatic evolution of southwestern North America during the Late Mesozoic

The composite Guerrero Terrane of western Mexico records much of the magmatic evolution of southwestern North America during Late Mesozoic time. The Guerrero includes three distinctive subterranes characterized by unique stratigraphic records, structural evolutions, and geochemical and isotopic features that strongly suggest they evolved independently. The eastern Teloloapan Subterrane represents an evolved intra-oceanic island arc of Hauterivian to Cenomanian age, which includes a high-K calc-alkaline magmatic suite. The central Arcelia–Palmar Chico Subterrane represents a primitive island arc-marginal basin system of Albian to Cenomanian age, consisting of an oceanic suite and a tholeiitic arc suite. The western Zihuatanejo–Huetamo Subterrane comprises three components that represent an evolved island arc-marginal basin-subduction complex system of Late Jurassic (?) –Early Cretaceous age built on a previously deformed basement. The Zihuatanejo Sequence includes a thick high-K calc-alkaline magmatic suite. The Las Ollas Complex consists of tectonic slices containing exotic blocks of arc affinity affected by high-pressure/low-temperature metamorphism included in a sheared matrix. The Huetamo Sequence consists mainly of volcanic-arc derived sedimentary rocks, including large pebbles of tholeiitic, calc-alkaline, and shoshonitic lavas. These sequences are unconformably underlain by the Arteaga Complex, which represents the subvolcanic basement. On the basis of available geology, geochemistry, geochronology, and isotopic data, we suggest that Late Mesozoic volcanism along the western margin of southern North America developed in broadly contemporaneous but different intra-oceanic island arcs that constitute a complex fossil arc-trench system similar to the present-day western Pacific island arc system.

A phylogenetic and geotectonic scenario to explain the biogeography of the Lophopidae (Hemiptera, Fulgoromorpha)

The Lophopidae are found in South America, Africa, Australia, India and Southeast Asia. This distribution appears to be typically Gondwanan, triggered by tectonic events beginning over 100 Ma. However, within the Fulgoromorpha, the lophopids are considered to be relatively recently. In this study, biological, geological and phylogenetic information is evaluated to provide a parsimonious explanation for the distribution of the group and its geographic region of ancestral origin. The Lophopidae can be divided into four monophyletic groups. The ancestors of two groups appear to have originated somewhere along the western Pacific island arc system. Another group appears to have an origin in Southeast Asia. A reliable explanation for the ancestral origin of the fourth group was not possible because it consists of only one genus present in Central and South America. A biogeographic map of the two groups of lophids of the western Pacific island arc is concordant with their phylogeny based on biological and morphological data. Based on this finding, the best explanation for the origin and evolution of the Lophopidae and their current distribution of these lophopids is through vicariance. Similar types of eco-evolutionary events explain radiation and distribution of the Lophopidae, in general.

Reassessment of the origin of the Dun Mountain Ophiolite, New Zealand: Nd‐isotopic and geochemical evolution of magma suites

Magmatic suites with contrasting isotopic and geochemical compositions, sequentially emplaced in different tectonic regimes, comprise the Dun Mountain Ophiolite Belt (DMOB), New Zealand. At D'Urville Island, the northernmost exposure of the DMOB, earliest erupted (stage 1) pillow basalts have ϵNd(T) = +6.3 to +7.5, and are incompatible element enriched, like basalts from geo‐chemically anomalous ridge segments. Overlying stage 2 basalts (sheeted flows) show a narrow range of ϵnd(T) = ‐8.3 ± 0.2, with chemical characteristics of depleted back‐arc basin basalts. These rocks are intruded by mafic to silicic stage 3 magmas, which have high uniform initial 143Nd/144Nd ratios (ϵNd(T) = +9.3 ± 0.2) over a wide range of 147Sm/144Nd values (yielding a precise Early Pemian Ndisotope age of 278 ± 4 Ma (MSWD = 0.48)). Stage 3 magmas show pronounced subduction‐related geochemical signatures similar to island arc tholeiites (IAT) from immature arcs. They are closely analogous to some (boninite)‐IAT magmas which characterise “infant arc” eruptive activity in forearc basins of present‐day Western Pacific island arc systems. A wide range of stage 3 magma compositions, ranging from near‐primary basaltic dikes (Mg# = 74) to extremely fractionated silicic plagiogranites with uniformly very depleted isotopic ratios, is consistent with slow spreading rates which gave rise to polybaric, closed‐system fractionation of magmas and periodic chamber abandonment. Some stage 3 rocks with SiO2 levels in the andesite range have low‐TiO2 contents and high Mg#, and may be fractionated equivalents of boninites. High ϵNd(T) values of stage 3 magmas indicate a lack of subducted sediment with inherited crustal residence signatures, and reflect the extent of supra‐subduction zone (SSZ) mantle wedge depletion. DMOB stage 3 magmas may represent forearc magmatism that was the precursor to normal subduction‐related volcanism established by c. 265 Ma in the Brook Street Arc and derived from a SSZ mantle source with identical Nd‐isotope characteristics. Less isotopically depleted stage 1 and 2 basalts (and rocks of the Lee River Group in general) may represent fragments of pre‐existing mafic ocean crust sensu stricto, as suggested by significantly older Nd‐isotopic ages for the basaltic seafloor volcanic component of the DMOB. Upon initiation of subduction, pre‐existing geochemically anomalous (possibly back‐arc basin) ocean crust (stage 1 and 2 magmas) was intruded by the “infant arc” (stage 3) magmas, as proposed for older seafloor remnants in forearc regimes of the Izu‐Bonin‐Mariana and Tonga arc systems.

Downed wood in Micronesian mangrove forests

Dead, downed wood is an important component of upland forest and aquatic ecosystems, but its role in wetland ecosystems, including mangroves, is poorly understood. We measured downed wood in ten sites on the western Pacific islands of Kosrae, Pohnpei, and Yap, all located within the Federated States of Micronesia. Our goals were to examine patterns of variability in the quantity of downed wood in these mangrove ecosystems, provide a general characterization of downed wood in a region with no previously published accounts, and investigate the relationship between harvesting practices and the amount of downed wood. The overall mean volume of downed wood at our study sites was estimated to be 60.8 m3 ha−1 (20.9 t ha−1), which is greater than most published data for forested wetlands. There were significant differences among islands, with the sites on Kosrae (104.2 m3 ha−1) having a much greater mean volume of downed wood than those on Pohnpei (43.1 m3 ha−1) or Yap (35.1 m3 ha−1). Part of the difference among islands may be attributable to differences in stand age and structure, but the most important factor seems to be the greater amount of wood harvesting on Kosrae, coupled with a low efficiency of use of cut trees. Of a total of 45 cut trees examined on Kosrae, no wood had been removed from 18 (40%); these are believed to be trees cut down because other, more valuable, trees were caught on them as they were felled. Of the other 27 trees, only 24 to 42% of the stem volume (to a 10 cm top) was removed from the forest, the amount varying by species. The impacts of current harvesting practices are unknown but may include important effects on tree regeneration and the abundance and species composition of crab populations.

Nutrition Related Cultural Issues and Body Mass Index (BMI) in a Western Pacific Island Population

Health and cultural practices have nutritional ramificationsbut little is known about the prevalence of such practices on populations in the Pacific. In this study, 400 randomly selected adults on Guam were surveyed via telephone. The sample reflected the ethnic distribution of the island, Chamorro (37%), Filipino (23%), Caucasian (14%), Multiple Ethnic (10%), Asian (7%), Pacific Islander (5%), and Black and other (4%). Data were compared among the various ethnic, age, and gender groups. Nutritional supplements were used by 42.3% of the sample, with Caucasians and Blacks using significantly more than the other ethnic groups. Betel nut, a traditional substance, was used by only 12%, primarily Chamorros and other Pacific Islanders. Caucasians and Asians reported no betel nut use. Occurrence of special diets was reported by 17%. Multiple Ethnic, Chamorro, and Caucasian groups had highest frequencies of special diets. Women were more likely to be on weight loss and men on athletic diets. Nearly everyone (89%) participated in fiestas, a cultural practice where large quantities of food are eaten. Average fiesta consumption was 1.7 ± 2.4 meals per month, but Chamorros ate significantly more, 2.3 ± 3.2. Because fiesta meals are high in calories this practice could promote obesity, which was prevalent in this sample. Mean BMI was 25.7 ± 5.8 with 27.1% in overweight and obese BMI categories. Chamorros had the highest mean BMI, 27.0 ± 5.8, while Filipinos and Asians had the lowest, 24.0 ± 4.4 and 22.5 ± 3.0, respectively. Nearly 40% of the Chamorros were in overweight and obese categories, while significantly fewer Filipinos and Asians were in those categories, 15.3% and 0%, respectively. Because these cultural and nutrition issues varied widely, health care professionals should stress the importance of a healthful lifestyle among all groups and give other advice where appropriate.

Pycnogonida from the Western Pacific Islands, XV. : Achelia cuneatis n. sp. and a Known Species from Sakhalin Island, Russian Far East

Pycnogonida from the Western Pacific Islands, XV. : Achelia cuneatis n. sp. and a Known Species from Sakhalin Island, Russian Far East

New Diterpene Lactones from the Sponge Spongia matamata

Chemical investigation of the sponge Spongia matamata, collected in the western Pacific Island of Yap, has resulted in the isolation of a pair of new spongian diterpenoid epimers 2 and 3, along with four other known spongians. The structures were determined by spectroscopic methods.

Pycnogonida of the Western Pacific Islands, XIV. A Shallow-water Collection from Tonga

Pycnogonida of the Western Pacific Islands, XIV. A Shallow-water Collection from Tonga

Radar observations of a 3‐day Kelvin wave in the equatorial mesosphere

Mesospheric radars are used to investigate the characteristics of a Kelvin wave from two equatorial sites: Jakarta, Indonesia, in the western Pacific and Christmas Island in the central Pacific. Our study focuses on the time span from mid‐January through mid‐October 1993. A Kelvin wave with a period near 3 days was detected throughout this 9‐month duration, although it underwent deep amplitude modulations on a ∼20‐day timescale. A fitting procedure is applied to study the phase/amplitude behavior of the wave. The vertical wavenumber was measured by the radars and found to be small, wandering around zero with only a weak bias toward downward phase progression. The long vertical wavelength suggests that the wave was predominantly zonal wavenumber 1. The amplitude of the wave measured by the Jakarta meteor scatter radar was much larger than the amplitude measured by the MF partial reflection radar at Christmas Island. The smaller wave amplitude at Christmas Island could at least partially be due to a measurement bias associated with MF radars. The radar at Jakarta is a VHF meteor scatter radar and is not susceptible to this bias. However, the mean velocities and the amplitudes of the tidal and quasi 2‐day wave components were in good agreement at the two sites. The estimated 9‐month averaged zonal acceleration was ∼0.67 ms−1 day−1 over Jakarta at 94–98 km and only about half as large over Christmas Island. The magnitude of the zonal acceleration occasionally showed large enhancements which suggest the importance of refractive effects associated with vertical and temporal variations in the mean winds. The larger 3‐day wave amplitudes and inferred acceleration at Jakarta may reflect its location in the western Pacific, a region of high convection, and hence an excitation region for equatorial waves. The relative phase of the wave between the two radar sites gradually shifted over a timescale of weeks. These smooth variations in relative phase are suggestive of a superposition of waves with different zonal wavenumbers, perhaps radiating preferentially from one longitude. The phase of the wave as a function of altitude and time was much more disordered at Jakarta than at Christmas Island. The conjecture can be made that the more chaotic phase structure observed over Jakarta is due to higher‐order zonal wavenumber components which weaken as they propagate eastward.