Records of pelagic copepods off Kaikoura,New Zealand   总被引：1，自引：1，他引：0  

Janet M. Bradford 《新西兰海洋与淡水研究杂志》2013,47(4):351-363

Additions to the pelagic copepod fauna of Kaikoura, New Zealand, include 20 species previously unrecorded and the males of 8 species for which females only had been recorded; further information concerning 2 other species is added.  相似文献   

Comment on Stadmark and Conley (2011) "Mussel farming as a nutrient reduction measure in the Baltic Sea: consideration of nutrient biogeochemical cycles"     

Rose JM  Ferreira JG  Stephenson K  Bricker SB  Tedesco M  Wikfors GH 《Marine pollution bulletin》2012,64(2):449-51; author reply 455-6

  相似文献   

Discrimination of tropical vegetation types using SPOT multispectral data     

Janet Franklin 《国际地球制图》2013,28(2):57-63

Vegetation types were discriminated using SPOT multispectral data on Miti'aro, a tropical oceanic island in the Cook Islands, Polynesia. Vegetation categories included undisturbed and disturbed forest on limestone, scrub, marsh, and other forest vegetation (including secondary upland forest and agroforestry). Most category pairs had high separability as measured by Jeffries‐Matusita distance and Euclidean distance for training site data. However, there was some class overlap as illustrated by unsuperaised clustering and assigning spectral clusters to vegetation classes using a reference map. Cloud cover was a problem encountered in optical imaging of this maritime tropical study area.  相似文献   

Response of xenotime to prograde metamorphism     

Birger Rasmussen  Ian R. Fletcher  Janet R. Muhling 《Contributions to Mineralogy and Petrology》2011,162(6):1259-1277

Xenotime is a widespread accessory mineral in lower greenschist to upper amphibolite facies metasedimentary rocks from the Palaeoproterozoic Mount Barren Group, southwestern Australia. Xenotime is closely associated with detrital zircon, commonly forming syntaxial outgrowths, in samples of sandstone, micaceous quartzite, slate, phyllite, garnet-bearing semi-pelites, and in kyanite-, garnet-, and staurolite-bearing mica schists. In situ geochronology of xenotime from lower greenschist sandstones has previously yielded multiple U–Pb ages with peaks at ~2.0, ~1.7, and ~1.65 Ga, interpreted to represent the age of detritus, early diagenesis, and a later thermal event, respectively. New U–Pb dating of xenotime in slate yields a major population at ~1.7 Ga with a minor population at ~1.2 Ga, reflecting diagenetic and metamorphic growth, respectively, whereas xenotime in phyllite forms a minor age population at ~1.7 Ga and a main peak at ~1.2 Ga. Mid-greenschist facies semi-pelitic schists (quartz-muscovite-garnet) contain xenotime that formed before 1.8 Ga and at 1.2 Ga, representing detrital and peak metamorphic ages, respectively. Xenotime in samples of amphibolite facies schist (650°C and ~8 kbars) yields U–Pb ages of ~1.2 Ga, coinciding with the time of peak metamorphism. A single analysis of a xenotime core from an amphibolite facies schist gave an age of ~1.8 Ga, consistent with the presence of detrital xenotime. Our results suggest that detrital xenotime may be preserved under greenschist facies conditions, but is largely replaced during upper amphibolite facies conditions. Detrital xenotime is replaced through dissolution–reprecipitation reactions forming compositionally distinct rims during greenschist and amphibolite facies metamorphism at 1.2 Ga. Diagenetic xenotime is present in lower greenschist facies samples, but was not observed in metasedimentary rocks that had experienced temperatures above mid-greenschist facies metamorphism (450°C). The apparent disappearance of detrital and diagenetic xenotime and appearance of metamorphic xenotime during prograde metamorphism indicates that some of the yttrium, heavy rare earth elements, and phosphorus needed for metamorphic xenotime growth are probably derived from the replacement of detrital and diagenetic xenotime.  相似文献   

Annual,Seasonal, and Regional Variability in Diet of Atlantic Croaker (<Emphasis Type="Italic">Micropogonias undulatus)</Emphasis> in Chesapeake Bay     

Janet A. Nye  David A. Loewensteiner  Thomas J. Miller 《Estuaries and Coasts》2011,34(4):691-700

Atlantic croaker is one of the most abundant demersal fish in Chesapeake Bay. Until recently, when substantial declines in abundance have occurred, high biomass supported elevated fisheries landings. Therefore, study of the diet of Atlantic croaker is important to understand its own dynamics and its role in the Chesapeake Bay ecosystem. Patterns in the diet of croaker varied annually, seasonally, and spatially, but were not strongly correlated with any measured environmental variables. Although the majority of the diet of croaker consisted of polychaetes and other benthic items, about 20% of the croaker diet by weight consisted of anchovy and other fishes. Croaker consumption of anchovy is likely a result of crepuscular feeding that has not been captured in previous studies that sampled during the day and with bottom trawls. Thus, croaker influences both the benthic and pelagic components of the Chesapeake Bay food web and incorporating such diel patterns in diet may increase the reliability of fishery ecosystem models.  相似文献   

Timing and mechanisms controlling evaporite diapirism on Ellef Ringnes Island,Canadian Arctic Archipelago     

Jennifer Boutelier  Tom Brent  Randell Stephenson 《Basin Research》2011,23(4):478-498

The Permo‐Carboniferous to Eocene Sverdrup Basin in Canada's Arctic Archipelago is strongly influenced by evaporite diapirism. However, salt structures within the basin have not been extensively investigated recently due to their remote location. This study includes the interpretation of legacy seismic reflection and borehole data to characterize the geometry of selected evaporite domes, and 1D backstripping of wells to investigate tectonic and sedimentary influences on diapirism. Extensional rift‐structures appear to have played a significant role in the formation of evaporite domes by triggering and directing salt movement. Diapirism was initiated by at least the Middle Triassic and continued to develop during the Mesozoic. Differential loading of salt on opposing east–west dome margins led to their present day asymmetric geometries. Diapir growth rates in the Mesozoic were closely linked to the rate of sedimentation and influenced by regional tectonism.  相似文献   

The radiometric age of the Albany Granite and the Stirling Range Beds,Southwest Australia     

A. Turek  N. C. N. Stephenson 《Australian Journal of Earth Sciences》2013,60(2):449-456

The reported age of 1,100 ± 50 m.y. for the Albany Granite is taken as marking the waning stages of the main orogeny in the south coast of Western Australia. The high initial ⁸⁷Sr/⁸⁶Sr for this granite, 0.7118 ± 0.0064, suggests an anatectic or rheomorphic origin which is consistent with petrographic evidence for the absence of a later metamorphism. Shales from the Stirling Range Beds indicate a metamorphic event at 1,150 ± 40 m.y. which is considered to be the time of upthrusting of rocks of higher metamorphic grade to their present position adjacent to the Stirling Range Beds. The minimum age of deposition for the Stirling Range Beds is postulated as 1,340 m.y.  相似文献   

The petrology of the Mt Manypeaks Adamellite and associated high‐grade metamorphic rocks near Albany,Western Australia     

N. C. N. Stephenson 《Australian Journal of Earth Sciences》2013,60(4):413-439

The Mt Manypeaks Adamellite is a composite, regionally concordant pluton at least 22 km long and 3 km wide, associated with Precambrian amphibolite facies gneisses of the Albany‐Esperance Block, and situated about 35 km east of Albany, Western Australia. The pluton is surrounded by a granitised aureole, and shows structural and mineralogical harmony with the country rocks. Contacts vary from grada‐tional to sharp. Hence field relations are consistent with syn‐ or late‐kinematic emplacement in the catazone. The normative composition of the pluton corresponds with the thermal trough in the system An‐Ab‐Or‐Q‐H2O at 7 kb PH2O, suggesting an origin involving crystal‐melt equilibria. The pluton is believed to have formed almost in situ by partial anatexis of the country rocks at 700–750°C and a depth of about 25 km during the orogenic episode responsible for regional metamorphism and deformation.  相似文献   

Earthquake evidence for compressive stress in the southeast Australian crust   总被引：1，自引：1，他引：0  

David Denham  Janet Weekes  Clementine Krayshek 《Australian Journal of Earth Sciences》2013,60(3-4):323-332

Earthquakes in SE Australia are usually caused by compressive stresses acting in the crust, and are associated with steeply dipping faults. Sometimes the faulting is predominantly strike‐slip, as for the Bowning earthquakes of 1977 and some of the Dalton/Gunning earthquakes; and sometimes it is high‐angle thrust faulting, as for the 1961 Robertson and 1973 Picton earthquakes. No surface expression of the faults associated with any recent earthquakes in SE Australia has been reported.

The directions of the pressure axes, from all the earthquakes for which focal mechanisms have been determined, do not form a consistent pattern. This suggests that the faulting associated with earthquakes in SE Australia is dominated by the geometry of pre‐existing crustal faults or zones of weakness.

In situ stress measurements have not been made near the epicentral areas of the larger recent earthquakes, because of the absence of competent, near‐surface rocks coupled to the crust. However, in the western part of the Lachlan Fold Belt the in situ stress results indicate that the maximum pressure axis is approximately E‐W. The evidence from the focal mechanisms does not preclude the persistence of this stress regime farther to the east, and a regional compressive stress in the crust with an azimuth of about 120° is consistent with most of the earthquake focal mechanisms and the in situ stress measurements throughout SE Australia.  相似文献   

1D PetroMod software modeling of the Basrah oil fields, Southern Iraq     

Thamer K. Al-Ameri  Mohamed S. A. Jafar  Janet Pitman 《Arabian Journal of Geosciences》2013,6(10):3783-3808

1D (Petromod) hydrocarbon charge modeling and source rock characterization of the Lower Cretaceous and Upper Jurassic underlying the prolific Cretaceous and Tertiary reservoirs in the Basra oilfields in southern Iraq. The study is based on well data of the Majnoon, West Qurna, Nahr Umr, Zubair, and Rumaila oil fields. Burial histories indicate complete maturation of Upper Jurassic source rocks during the Late Cretaceous to Paleogene followed by very recent (Neogene) maturation of the Low/Mid Cretaceous succession from early to mid-oil window conditions, consistent with the regional Iraq study of Pitman et al. (Geo Arab 9(4):41–72, 2004). These two main phases of hydrocarbon generation are synchronous with the main tectonic events and trap formation associated with Late Cretaceous closure of the neo-Tethys; the onset of continent–continent collision associated with the Zagros orogeny and Neogene opening of the Gulf of Suez/Red Sea. Palynofacies of the Lower Cretaceous Sulaiy and Lower Yamama Formations and of the Upper Jurassic Najmah/Naokelekan confirm their source rock potential, supported by pyrolysis data. To what extent the Upper Jurassic source rocks contributed to charge of the overlying Cretaceous reservoirs remains uncertain because of the Upper Jurassic Gotnia evaporite seal in between. The younger Cretaceous rocks do not contain source rocks nor were they buried deep enough for significant hydrocarbon generation.  相似文献