Effects of differential tectonic uplift on Late Quaternary coral reef diagenesis,Huon Peninsula,Papua New Guinea     

Z. Zhu  J. F. Marshall  J. Chappell 《Australian Journal of Earth Sciences》2013,60(5):463-474

Mineralogical, petrological and geochemical analyses of corals and associated skeletal limestones taken from three transects across the Late Quaternary raised coral reefs of the Huon Peninsula, Papua New Guinea, show that tectonic uplift can be related to the degree of subaerial diagenesis of the reefs. Where the uplift rate is high, Pleistocene corals frequently retain their aragonite mineralogy, even though the annual rainfall is relatively high. In contrast, similar age corals from low‐uplift areas are consistently altered neomorphically to calcite. The transformation of reef skeletal limestones shows a similar, but less pronounced, trend to the corals. Chemical analysis shows that the neomorphic calcite crystals of coral skeletons from the low‐uplift areas have relatively higher Sr and Mg concentrations, compared with those in high‐uplift areas. This may indicate that neomorphism of corals in the low‐uplift terraces takes place at a relatively higher rate and an earlier stage than that in the high‐uplift areas. The pattern of diagenesis of the Huon reefs can be explained by the effects of tectonic uplift on the regional hydrological regime. First, lower uplift rates allow a raised reef or any part of it to remain in the meteoric phreatic zone for a relatively long time. Second, river gorge slopes from low‐uplift regions have lower gradients and reef terraces in these areas have more extensive raised lagoon depressions than in high‐uplift areas. Thus, there is less runoff and consequently more extensive vadose percolation in the former areas. Third, the resulting low‐relief topography in low‐uplift areas prompts formation of soils on the terraces, and further increases the ability of interaction between coral reefs and formation water.  相似文献   

A first look at oxygen isotope records from modern and Holocene-aged gastropod (Stenomelania) shells from Lake Kutubu,Papua New Guinea     

Kelsie Long  Larissa Schneider  Ian S. Williams  Stewart J. Fallon  Hilary Stuart-Williams  Simon Haberle 《第四纪科学杂志》2020,35(3):457-464

The oxygen isotopic composition of Stenomelania gastropod shells was investigated to reconstruct Holocene palaeoclimate change at Lake Kutubu in the southern highlands of Papua New Guinea. Oxygen isotope (δ¹⁸O) values recorded in aquatic gastropod shells change according to ambient water δ¹⁸O values and temperature. The gastropod shells appear to form in oxygen isotopic equilibrium with the surrounding water and record a shift in average shell oxygen isotopic composition through time, probably as a result of warmer/wetter conditions at ca. 600–900 and 5900–6200 cal a bp. Shorter term fluctuations in oxygen isotope values were also identified and may relate to changes in the intensity or source of rainfall. Further δ¹⁸O analyses of gastropod shells or other carbonate proxies found in the Lake Kutubu sediments are warranted. © 2020 John Wiley & Sons, Ltd.  相似文献   

Reef microhabitats mediate fish feeding intensity and agonistic interactions at Príncipe Island Biosphere Reserve,Tropical Eastern Atlantic     

Angela Marina Canterle  Lucas Teixeira Nunes  Luisa Fontoura  Hugulay Albuquerque Maia  Sergio Ricardo Floeter 《Marine Ecology》2020,41(5):e12609

The benthic assemblage of reefs provides an important resource of food and habitat for reef fishes. However, how benthic composition mediates reef fishes' biotic interactions at isolated environments such as oceanic islands remains largely unknown. Here, we aimed to investigate the role of four different reef microhabitats over biological interactions of fishes in an understudied oceanic island, Príncipe Island. For that, we recorded a total of 46 Underwater Remote Videos (RUVs) to document benthic composition and fishes' trophic and agonistic interactions. We used benthic cover estimates to group the samples into four microhabitats (dominated by epilithic algal matrix [EAM], sand/rock, corals and sponges), then quantified fishes' trophic and agonistic interactions in each microhabitat. All microhabitats presented a different structure of trophic and agonistic interactions of the fish assemblage. Feeding pressure (FP) and agonistic interactions were higher on the EAM microhabitat and lower in coral microhabitat. Herbivores were the main responsible group for the FP in all microhabitats. Territorial damselfishes used microhabitats differently for both trophic and agonistic interactions. We demonstrated that reef fish diversity and intensity of biotic interactions varied according the spatial distribution of benthic resources, which suggests that benthic composition plays an important role on structuring biological interactions at isolated reef systems.  相似文献   

Age and provenance of basement metasediments from the Kubor and Bena Bena Blocks,central Highlands,Papua New Guinea: Constraints on the tectonic evolution of the northern Australian cratonic margin     

N. Van Wyck  I. S. Williams 《Australian Journal of Earth Sciences》2013,60(3):565-577

Detrital zircon from two basement blocks (Kubor and Bena Bena) in the central Highlands of Papua New Guinea has an age signature that strongly suggests a northern Australian provenance. Samples of the Omung Metamorphics, southeastern Kubor Block, together yield principal zircon populations with ages of ca 1.8 Ga (～10% of the total), ca 1.55 Ga (～10%), 470–440 Ma (～15%), ca 340 Ma (～10%) and 290–260 Ma (～40%).Two tonalite stocks of the Kubor Intrusive Complex, which intrude the Omung Metamorphics, yield indistinguishable ages of 244.8 ± 4.9 Ma and 239.1 ± 4.2 Ma.Therefore, the deposition and subsequent deformation of the Omung Metamorphics is Late Permian to Early Triassic. A sample of Goroka Formation (Bena Bena Block) contains detrital zircon of similar ages to the Omung Metamorphics, ca 1.8 Ga (5%), ca 1.55 Ga (～45%), ca 430 Ma (～5%) and ca 310 Ma (～40%), suggesting that the Goroka Formation has a similar provenance and might be correlative. In contrast, a metapsammite from the Bena Bena Formation yielded only ages of 290–280 Ma (85%) and ca 240 Ma (15%). A tuff interbedded in the Bena Bena Formation yielded only igneous zircon with a Late Triassic age of 221 ± 3 Ma. Contrary to previous interpretations, the Bena Bena Formation is probably younger than the Goroka Formation. Ages of New Guinea detrital zircon closely match those of igneous and detrital zircon from the Coen Inlier, northeastern Queensland, but contrast with the ages of zircon from terranes further south, east and west. The Kubor and Bena Bena Blocks are not suspect terranes, but rather form part of the Australian craton. The craton margin, modified by rifting during the Mesozoic, was re‐inverted during Cenozoic compression. The Australian craton, in the eastern Highlands of Papua New Guinea, extends at least as far north as the Markham Valley, the northern edge of the Bena Bena terrane.  相似文献   

Spatial heterogeneity of macrofaunal communities in and near a giant pockmark area in the deep Gulf of Guinea     

Lénaïck Menot  Joëlle Galéron  Karine Olu  Jean-Claude Caprais  Philippe Crassous  Alexis Khripounoff  & Myriam Sibuet 《Marine Ecology》2010,31(1):78-93

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Bottlenose dolphin Tursiops truncatus at São Tomé Island (São Tomé and Príncipe) — relative abundance,site fidelity and social structure     

《African Journal of Marine Science》2013,35(4):501-510

Although the bottlenose dolphin Tursiops truncatus is one of the most common cetacean species around São Tomé Island, Gulf of Guinea, little research has focused on this species in this region. This study investigated the population of bottlenose dolphins around São Tomé Island by estimating the minimum population size, site fidelity and social structure. During a total of 226 surveys between 2002 and 2006, and in 2012, 51 sightings were recorded but only 33 had photographic data suitable for rigorous analysis. The minimum annual total population size, based on permanently marked dolphins, was 37 individuals, and the discovery curve indicated that a large part of the population remained undiscovered. The annual sighting rate for 76 highly distinctive adult animals ranged from 0.20 (seen in one year only) to 1.0 (seen every year of the study period). Resighted individuals demonstrated low association values; the dolphins seemed to form a single group with a fluid structure.  相似文献   

几内亚优势金属矿产地质特征、成矿作用及开发现状     

张海坤  胡鹏  程湘  姜军胜  刘江涛  向鹏 《地质通报》2022,(1):141-153

几内亚大地构造位置处于西非克拉通南部,主要受Libérien、Eburnéen及泛非三次大的造山运动影响,主要的地质单元包括东部太古宙—古元古代马莱地盾、西部古生代博法(Bove)盆地和西南部泛非期Rokelide造山带.在广泛调研文献的基础上,着重介绍了几内亚铝土矿、铁、金等矿产资源的开发现状.结合区域地质背景和典型...  相似文献   

Environmental Refugees? A tale of two resettlement projects in coastal Papua New Guinea     

John Connell  Nancy Lutkehaus 《The Australian geographer》2017,48(1):79-95

ABSTRACT

Environmental change in small islands may be associated with migration as a means of adaptation. Both Manam and the Carteret Islands in Papua New Guinea (PNG) have experienced rapid- and slow-onset changes, respectively. These have been accompanied by the forced migration and ‘temporary’ resettlement of the Manam population and attempts at resettlement by Carteret Islanders. Neither has proved successful, thwarted by ‘host’ landowners, the impossibility of gaining adequate access to land and land rights, and government inactivity. Settlers have been perceived as outsiders and rival claimants to valuable coastal resources. Inability to resettle in national contexts raises issues of ambiguity, identity and citizenship. The problems experienced by quite small population groups moving short distances in similar cultural contexts are indicative of the potential future problems facing environmental migrants in other contexts.  相似文献   

Ocean variability North of New Guinea derived from TRITON buoy data     

Yuji Kashino  Iwao Ueki  Yoshifumi Kuroda  Andri Purwandani 《Journal of Oceanography》2007,63(4):545-559

We investigated variability in the ocean surface-subsurface layer north of New Guinea using Triangle Trans-Ocean Buoy Network (TRITON) buoys at 2°N, 138°E and 0°N, 138°E during the period from October 1999 to July 2004. Both North and South Pacific waters were observed below the subsurface at these stations. The variability in the subsurface waters was particularly high at 2°N, 138°E. Clear interannual variability occurred near the surface; the water type differed before and after onset of the 2002–03 El Niño. Before summer 2001, water that appeared to be advected from the central equatorial Pacific occupied the near surface layer. After autumn 2001, waters advected by the New Guinea Coastal Current were observed near the surface. Intraseasonal and seasonal variations were also observed below the subsurface. With regard to seasonal variability, the salinity of the subsurface saline water, the South Pacific Tropical Water, was generally high during the boreal summer-autumn, when the New Guinea Coastal Undercurrent was strong. Intraseasonal fluctuations on a scale of 20 to 60 days were also seen and may have been associated with intrinsic oceanic variability, such as ocean eddies, near the stations. Ocean variability in the thermocline layer between 100 and 200 m greatly affects the surface dynamic height variability; water variability before 2001 and variability in the pycnocline depth after 2002 are important factors affecting the thermocline.  相似文献   

A simple model for calculating tsunami flow speed from tsunami deposits   总被引：2，自引：0，他引：2  

Bruce E. Jaffe  Guy Gelfenbuam 《Sedimentary Geology》2007,200(3-4):347-361

This paper presents a simple model for tsunami sedimentation that can be applied to calculate tsunami flow speed from the thickness and grain size of a tsunami deposit (the inverse problem). For sandy tsunami deposits where grain size and thickness vary gradually in the direction of transport, tsunami sediment transport is modeled as a steady, spatially uniform process. The amount of sediment in suspension is assumed to be in equilibrium with the steady portion of the long period, slowing varying uprush portion of the tsunami. Spatial flow deceleration is assumed to be small and not to contribute significantly to the tsunami deposit. Tsunami deposits are formed from sediment settling from the water column when flow speeds on land go to zero everywhere at the time of maximum tsunami inundation. There is little erosion of the deposit by return flow because it is a slow flow and is concentrated in topographic lows. Variations in grain size of the deposit are found to have more effect on calculated tsunami flow speed than deposit thickness. The model is tested using field data collected at Arop, Papua New Guinea soon after the 1998 tsunami. Speed estimates of 14 m/s at 200 m inland from the shoreline compare favorably with those from a 1-D inundation model and from application of Bernoulli's principle to water levels on buildings left standing after the tsunami. As evidence that the model is applicable to some sandy tsunami deposits, the model reproduces the observed normal grading and vertical variation in sorting and skewness of a deposit formed by the 1998 tsunami.  相似文献