Geology of the Atlantis Massif (Mid-Atlantic Ridge, 30° N): Implications for the evolution of an ultramafic oceanic core complex     

Blackman  Donna K.  Karson  Jeffrey A.  Kelley  Deborah S.  Cann  Johnson R.  Früh-Green  Gretchen L.  Gee  Jeffrey S.  Hurst  Stephen D.  John  Barbara E.  Morgan  Jennifer  Nooner  Scott L.  Ross  D. Kent  Schroeder  Timothy J.  Williams  Elizabeth A. 《Marine Geophysical Researches》2002,23(5-6):443-469

Marine Geophysical Research - The oceanic core complex comprising Atlantis Massif was formed within the past 1.5–2 Myr at the intersection of the Mid-Atlantic Ridge, 30° N, and the...  相似文献   

The genus Neomonoceratina(Crustacea: Ostracoda) from the Cainozoic of the West Pacific margins     

Zhao Quanhong  Robin Whatley 《海洋学报(英文版)》1988,7(4):562-577

Fourteen species of Neomonoceratina from the West Pacific margins are considered in the present paper, of which two species and one subspecies are described as new. Lectotypes have been designated for three of Brady's 1868 species (N. bataviana, N. iniqua and N. rhomboidea) and also for two of Kingma's 1948 species (N. macropora and N. microreticulata).The taxonomic confusion within the genus, particularly with respect to N. crispata, N. delicata, N. dongtaiensis, N. iniqua and N. microreticulata, is clarified and the zoogeographical implication of the distribution of the genus is discussed.  相似文献   

大西洋中脊轴外新发现的热液泉(30°N)     

Deborah S Kelley  张光威 《海洋地质前沿》2002,18(1)

越来越多的证据表明 :热液泉不仅沿大洋中脊分布 ,也出现在远离扩张中心的老洋壳地区。北纬 3 0°的大西洋中脊和大西洋断裂带的东部发现了一个大的热水田 ,泉口区与已知的海底热水田明显不同 ,因为它处在 1 .5Ma的老洋壳上 ,距扩张轴约 1 5km,热泉的热驱动可能源自海水和地幔熔岩间放热蛇纹岩化的反应。这些热水泉分布在似圆丘状的断块山上 ,陡侧发育碳酸盐烟囱 ,为典型的黑烟囱热水田硫化物构造。泉口液体的温度较低 ( 40～ 75℃ )、偏碱性 ( p H9.0～ 9.5) ,并维系了包括耐热厌氧菌在内的稠密的微生物群体的存在。因大西洋断块的地质特…  相似文献   

Zum Gesellschaftsproblem in der Limnobiocoenologie     

Rich A. Vollenweider 《Aquatic Sciences - Research Across Boundaries》1948,10(4):53-64

Ohne Zusammenfassung  相似文献   

Ar-Ar dating of authigenic K-feldspar: Quantitative modelling of radiogenic argon-loss through subgrain boundary networks   总被引：2，自引：0，他引：2  

D.F. Mark  S.P. Kelley  J. Parnell  D.J. Brown 《Geochimica et cosmochimica acta》2008,72(11):2695-2710

We have analysed two distinct generations of authigenic K-feldspar in Fucoid Bed sandstones from An-t-Sron and Skiag Bridge, NW Highlands, Scotland, which have experienced post-growth heating to levels in excess of the predicted Ar-closure temperature. Authigenic K-feldspars show microtextural similarities to patch perthites; that is subgrains separated by dislocation-rich boundary networks that potentially act as fast diffusion pathways for radiogenic argon.The two generations of authigenic K-feldspar in the Fucoid Bed sandstones can be distinguished by different microtextural zones, bulk mineral compositions, fluid-inclusion populations, and inferred temperatures and chemistries of parent fluids. Ar-Ar age data obtained using high-resolution ultraviolet laser ablation, show that the first cementing generation is Ordovician and the second cementing generation is Silurian.Modelling of Ar diffusion using subgrain size as the effective diffusion dimension and a simplified tectono-thermal thrust model assuming transient heating of the Fucoid Beds is inconsistent with observed data. Removal of heat from the thrust zone through rapid flushing of heated fluids rather than transient heating can be invoked to explain the observed Ar-Ar ages for both generations of cement. Alternatively, Ar-diffusion modelling using overgrowth thickness as the effective diffusion dimension instead of subgrain size also yields models that are consistent with both the Fucoid Bed palaeothermal maxima and determined Ar-Ar age ages for the two generations of K-feldspar cement. Based on this alternate explanation, we propose a theoretical microtextural model that highlights fundamental differences between the microtextures of deuterically formed patch perthites and authigenic K-feldspars, explaining the apparent robustness of authigenic K-feldspar with respect to Ar-retention.  相似文献   

Assessing the transition from deforestation to forest regrowth with an agent-based model of land cover change for south-central Indiana (USA)   总被引：1，自引：0，他引：1  

Tom P. Evans  Hugh Kelley 《Geoforum》2008,39(2):819-832

The Midwest and Northeast United States has experienced a net increase in forest cover since the beginning of the 20th century. However, we lack a detailed understanding of the transition to net forest cover increase because this forest regrowth occurred prior to the use of tools like household-level surveys focused on land use decision-making and availability of remote sensing data. Agent-based modeling presents an appealing means to explore what social and biophysical dynamics may have contributed to this forest regrowth process. In this paper we employ an agent-based model to analyze the process of forest regrowth in south-central Indiana from 1939 to 1993. Simulation results are presented for assumptions regarding pre-existing forest age and the stand age at which landowners harvest timber with a goal of understanding the influence of these factors on future trajectories of land cover change. The results demonstrate both the value and the burden of having many time points to evaluate the success of the model. Is the best simulation the one with the smallest net residuals across all time points? Or is the best simulation the one that best reproduces the correct trajectory of land cover change for each time interval? Model simulations that assume a harvesting frequency of 30 years all produced landscapes within 2% of the actual forest cover in 1993, the end point of the study period. However, the trajectories of these simulations did not all mimic the gradual forest regrowth found in our observed data. The model simulation with the smallest residual values across all time points assumed a initial forest age of 5 years in 1939 and a harvesting frequency of 30 years. Ultimately, we cannot definitively conclude that one model simulation is a better representation of reality than another because we have no way of comprehensively validating the model assumptions. However, we can more plausibly conclude that the age of forest regrowth in 1939 and the frequency of timber harvesting by landowners both had an influence on the successive trajectory of land cover change in the study area.  相似文献   

A distant magmatic source for Cretaceous karst bauxites of Southern Apennines (Italy), revealed through SHRIMP zircon age dating     

Maria Boni  Steven M. Reddy  Nicola Mondillo  Giuseppina Balassone  Rich Taylor 《地学学报》2012,24(4):326-332

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The ocean’s role in the transient response of climate to abrupt greenhouse gas forcing     

John Marshall  Jeffery R. Scott  Kyle C. Armour  J.-M. Campin  Maxwell Kelley  Anastasia Romanou 《Climate Dynamics》2015,44(7-8):2287-2299

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Modeling IR spectral energy distributions: a?pilot study of?starburst parameters and silicate absorption curves for some GOALS galaxies     

Michael A. Dopita  Lee Armus  Lisa J. Kewley  Jeff A. Rich  Dave Sanders  Phillip N. Appleton  Ben H. P. Chan  Vassilis Charmandaris  Aaron S. Evans  David T. Frayer  Justin H. Howell  Hanae Inami  Joseph A. Mazzarella  Andreea Petric  Sabrina Stierwalt  Jason Surace 《Astrophysics and Space Science》2011,333(1):225-239

This paper describes a pilot study into the spectral energy distribution (SED) fitting and the derivation of physical parameters for 19 galaxies observed as part of the Great Observatories All-sky LIRG Survey (GOALS) survey as observed with the Spitzer Space Telescope. For this we have used the pan-spectral fitting tools developed in a series of papers by Dopita and his co-workers. We show that the standard Lee and Draine ??astronomical silicate?? model cannot provide a good fit to the silicate absorption features as observed in the heavily dust-extinguished (A _V??50 mag.) starbursts. We have derived an empirical fit to the ??starburst silicate?? absorption in these objects. This absorption curve is consistent with the silicate grains being systematically larger in starburst environments than in the local Galactic interstellar medium. We demonstrate the sensitivity of the SED fitting to each of the fitted parameters, and derive these parameters for those galaxies which do not have an embedded AGN. This technique is simple and provides reasonably robust and uniform parameters for the starburst, especially as far as the star formation rate, population of old stars, compactness of the starburst region and total foreground extinction are concerned. However, the chemical abundances and the optical extinction cannot be reliably determined by this analysis, and optical SEDs will also be required to provide a complete characterization of the starburst region and of the surrounding galaxy.  相似文献   

Radiocarbon dates and the genesis of phytogenic near-shore sediments on St. Catherines Island,Georgia, USA     

Fredrick J. Rich  Lee Newsom  Brian Meyer  R. Kelly Vance 《Environmental Earth Sciences》2014,72(8):2985-2997

St. Catherines Island consists of a complex association of Pleistocene and Holocene sediments. The geographic location of the island at the center of Georgia Bight, a prominent re-entrant in the coastline of the southeastern USA, has resulted in the development of a very complex depositional and erosional history. For over 40,000 years the island has experienced a variety of physical, biological, and anthropological changes brought about by climatic, biotic, depositional, and anthropogenic events. Sedimentary deposits have been studied using diverse research tracks including palynology, dendrology, sedimentology, geophysics, and radiocarbon chronology, as well as archaeological techniques. This research focused on the interpretation of environments of deposition of strata that are exposed within the present surf zone, yet which bear the distinct signatures of upland/inland environments of deposition. Data derived from Late Pleistocene and Holocene accumulations of peat and mollusc- and wood-bearing muddy strata of certain on-shore and near-shore origins reveal diverse events relating to shoreline dynamics, plant community changes, and net shoreward migration of this island during the Late Holocene.  相似文献