scholarly journals 40Ar/39Ar Ages and Geochemistry of Seamount Basalts from the Western Pacific Province

2022 ◽  
Vol 10 (1) ◽  
pp. 54
Author(s):  
Qian Liu ◽  
Limei Tang ◽  
Ling Chen ◽  
Peng Gao
Keyword(s):  
Geochemical Characteristics ◽  
Western Pacific ◽  
Primitive Mantle ◽  
Magma Source ◽  
Ocean Island Basalts ◽  
The Pacific ◽  
Three Samples ◽  
Formation And Evolution ◽  
Geochemical Profiles ◽  
The Western Pacific

Seamounts are features generated by hot spots and associated intraplate volcanic activity. The geochemical characteristics of igneous rocks constituting seamounts provide evidence of important details of dynamic processes in the Earth, such as mantle magma source areas, and are key to understanding how mantle plume processes control the formation and evolution of seamounts and their resulting geochemical characteristics. The Pacific Ocean contains a large number of hitherto unstudied seamounts, whose ages and geochemical characteristics remain poorly known. This study presents the geochemical characteristics of six basalt samples from five seamounts in the Western Pacific and the 40Ar/9Ar ages of three samples are determined. The new analysis yielded 40Ar/39Ar ages for seamounts samples MP3D21, MP5D11, and MP5D15A of 95.43 ± 0.33, 62.4 ± 0.26, and 99.03 ± 0.4 Ma, respectively. The geochemical profiles of seamounts samples MP3D04, MP3D21, MP5D11, MP5D15A, MPID201, and MPID202 are consistent with alkaline basalts, as evidence by alkali-rich, silicon-poor compositions along with high titanium concentrations. The primitive mantle normalized rare-earth elements and trace elements spider pattern are similar to those of ocean island basalts. The Ta/Hf and Nb/Zr ratios and La/Zr-Nb/Zr discriminant diagrams indicate that the six seamounts formed from magma that originated in the deep mantle.

scholarly journals Annonaceae in the Western Pacific: geographic patterns and four new species

2017 ◽  
Author(s):  
Ian M. Turner ◽  
Timothy M.A. Utteridge
Keyword(s):  
New Species ◽  
Solomon Islands ◽  
New Guinea ◽  
Western Pacific ◽  
New Combinations ◽  
Geographic Patterns ◽  
The Pacific ◽  
Two New Species ◽  
The Western Pacific ◽  
A New Species

The taxonomy and distribution of Pacific Annonaceae are reviewed in light of recent changes in generic delimitations. A new species of the genus Monoon from the Solomon Archipelago is described, Monoon salomonicum I.M.Turner & Utteridge sp. nov., together with an apparently related new species from New Guinea, Monoon pachypetalum I.M.Turner & Utteridge sp. nov. The confirmed presence of the genus in the Solomon Islands extends the generic range eastward beyond New Guinea. Two new species of Huberantha are described, Huberantha asymmetrica I.M.Turner & Utteridge sp. nov. and Huberantha whistleri I.M.Turner & Utteridge sp. nov., from the Solomon Islands and Samoa respectively. New combinations are proposed: Drepananthus novoguineensis (Baker f.) I.M.Turner & Utteridge comb. nov., Meiogyne punctulata (Baill.) I.M.Turner & Utteridge comb. nov. and Monoon merrillii (Kaneh.) I.M.Turner & Utteridge comb. nov. One neotype and four lectotypes are designated. The geographic patterns exhibited by nine native Annonaceae genera, that range in the Pacific beyond New Guinea, are discussed.

Eastward Eddy Shedding of the Asian Summer Monsoon Anticyclone

2021 ◽  
Author(s):  
Xinyue Wang ◽  
William Randel ◽  
Yutian Wu
Keyword(s):  
North America ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Lower Troposphere ◽  
Western Pacific ◽  
The North ◽  
The Pacific ◽  
Asian Summer ◽  
The Western Pacific ◽  
Eddy Shedding

<p>Eastward eddy shedding of the Asian summer monsoon (ASM) anticyclone has a large impact on the chemical composition of the upper troposphere and lower stratosphere (UTLS) over the western Pacific. Here we investigate the dynamical mechanism of eastward eddy shedding in July and August using 41 years of the ERA5 6-hourly reanalysis data. We perform composite analyses of meteorological variables focusing on the eastward eddy shedding events with the presence of anticyclonic centers falling between 135<sup>•</sup>-140<sup>•</sup>E. The composited outgoing longwave radiation anomalies suggest enhanced convection near the Philippines Sea and the East China Sea one week beforehand. In the tropopause level, we see evident eastward propagating geopotential and meridional wind anomalies from the North Atlantic jet exit toward the western Pacific embedded along the extratropical westerly jet during day -10 to day 0. In the lower troposphere, we find that the geopotential anomalies aligned meridionally from the east Asian coast to the North Pacific to the northern North America during day -7 to day 0. The wave-activity flux is evaluated to identify the origin and propagation of the energy of the Rossby wave–like perturbation. In the UTLS we find a strong southeastward-pointing flux along 40<sup>•</sup>-50<sup>•</sup>N, resembling the Silk Road pattern. While in the lower troposphere, we also see a northeastward-pointing flux originating from tropical Philippine Sea across Japan to North America, resembling the Pacific-Japan pattern. Additional analysis is needed to study the relationship between the Silk Road pattern and the Pacific-Japan pattern.</p>

A review of the gobiid fish genus Trimma from the Chagos Archipelago, central Indian Ocean, with the description of seven new species

1984 ◽  
Vol 62 (4) ◽  
pp. 695-715 ◽  
Author(s):  
Richard Winterbottom
Keyword(s):  
New Species ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Western Pacific ◽  
Valid Species ◽  
Gobiid Fish ◽  
Central Indian Ocean ◽  
The Pacific ◽  
Chagos Archipelago ◽  
The Western Pacific

The genus Trimma contains 17 nominal and 13 valid species. Five of these are here reported from the Chagos Archipelago: T. eviotops, T. macrophthalma, T. mendelssohni. T. nauclei, and T. taylori. An additional 7 species arc described as new and another is described but not named, for a total of 13 species known from these islands. The biogeographic affinities of Chagos species of Trimma appear to lie with the western Indian Ocean rather than the western Pacific, but the evidence is weak because of the lack of knowledge of the Pacific Trimma fauna.

Geochemical characteristics and metal element enrichment in crusts from seamounts of the Western Pacific

2015 ◽  
Vol 10 (1) ◽  
pp. 171-182
Author(s):  
Xiaoyu Zhang ◽  
Kechao Zhu ◽  
Yong Du ◽  
Fuyuan Zhang ◽  
Weiyan Zhang ◽  
...  
Keyword(s):  
Geochemical Characteristics ◽  
Western Pacific ◽  
Metal Element ◽  
Element Enrichment ◽  
The Western Pacific

Bird extinctions in the central Pacific

1994 ◽  
Vol 344 (1307) ◽  
pp. 27-33 ◽  
Keyword(s):  
Endangered Species ◽  
Bird Species ◽  
Western Pacific ◽  
Extinction Rate ◽  
Human Occupation ◽  
Central Pacific ◽  
Fossil Species ◽  
The Pacific ◽  
Island Group ◽  
The Western Pacific

The first wave of human colonists spread across the Pacific from 4000 to 1000 years ago. That they caused many extinctions is well known from fossil finds. We estimate how many fossil species were missed - the answer is roughly half - and so estimate the true extinction rate. The first colonists exterminated roughly half the species on each island group. Some of these extinctions are falsely attributed to the first colonists, because intensive collection often began a half century after the damage initiated by European discovery. Even taken at face value, these recent extinctions are too few. Many species are so critically endangered that we know neither whether they still survive or how to save them. Interestingly, there are fewer recent extinctions and currently endangered species in the islands of the western Pacific, which were the islands occupied first by humans. We suggest that the species sensitive to human occupation died out long ago in these areas. If so, these islands would have lost even more than half of their bird species.

Sign in / Sign up

Export Citation Format

Share Document