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11.
Xiang-Yu Kou David K. Ferguson Jing-Xian Xu Yu-Fei Wang Cheng-Sen Li 《Climatic change》2006,77(3-4):431-448
The Eryuan palynoflora from the Late Pliocene of western Yunnan, China is described in this paper, and is compared with two contemporary palynofloras from Yangyi and Longling. The palynological data of the three locations are analyzed to reconstruct the climatic parameters of these areas at that time by using the Coexistence Approach. The Late Pliocene climatic parameters of Eryuan are estimated, i.e., the mean annual temperature ranged from 13.3 to 18.6∘C, the mean temperature of the warmest month from 24.6 to 27.5∘C, the mean temperature of the coldest month from 1.9 to 12.1∘C, the difference in temperatures of coldest and warmest month from 14.2 to 16.6∘C, the mean annual precipitation from 619.9 to 1484.3 mm, the mean maximum monthly precipitation from 143.8 to 245.6 mm, and the mean minimum monthly precipitation from 12.7 to 16.4 mm. Both paleovegetation and paleoclimate of the three localities are compared with the modern data at each location. The present study suggests a MAT decrease accompanied by a doubling of the MAP in the Longling area between the Late Pliocene and the present. This seems to be related to the uplift of Gaoligong Mountain in Longling which is now part of the eastern portion (Western Yunnan) of the Tibetan Plateau. 相似文献
12.
13.
C. C. Ferguson P. K. Harvey G. E. Lloyd 《Contributions to Mineralogy and Petrology》1981,75(4):339-352
Whether or not a growing porphyroblast can displace its surrounding matrix is an important but contentious issue affecting the interpretation of metamorphic textures. As an alternative to treating the problem in terms of force of crystallization, this paper examines the mechanics of porphyroblast-matrix interaction using a different and much simpler conceptual framework. New microstructural evidence for matrix displacement is then presented and analysed in detail. This evidence, from a hornfelsed metagreywacke, consists of dome-shaped accumulations of muscovite and graphite, each dome being attached to (and concave towards) a rhombdodecahedral face of a garnet porphyroblast. Muscovite within the domes shows a dimensional preferred orientation subparallel to the dome outlines while, in the matrix away from the domes, there is no preferred orientation.Our model for the origin of the mica domes envisages muscovite and graphite being swept ahead of, and mechanically accumulated onto, the growing garnet faces as they advance through the matrix. Rigorous testing of this model provides strong evidential support for matrix displacement by growing porphyroblasts. A new analysis is provided of the conditions under which matrix grains are included or displaced by porphyroblasts. It is concluded that matrix grain displacement may be very common, although the special combination of circumstances necessary to produce a diagnostic microstructural pattern probably occurs very rarely. 相似文献
14.
15.
The Winnipeg and Deadwood formations form deep clastic reservoirs in Saskatchewan, Canada, with temperatures exceeding 40 °C over most of southern Saskatchewan and reaching 100 °C in southwestern Saskatchewan. At these temperatures, the formations have geothermal potential for development of direct use and electricity generation systems. Numerous disposal wells operating at rates of 30 L/s or more are currently installed in these formations, suggesting that electricity could be generated at rates exceeding 2 megawatts of electrical output (MWe) from individual wells. These basal clastic units, thus, could provide significant energy supply over a broad region of Saskatchewan. 相似文献
16.
Susanne?M.?McDowellEmail author Calvin?F.?Miller Roland?Mundil Charles?A.?Ferguson Joseph?L.?Wooden 《Contributions to Mineralogy and Petrology》2014,168(1):1031
The Silver Creek caldera (southern Black Mountains, western Arizona) is the source of the 18.8 Ma, >700 km3 Peach Spring Tuff (PST) supereruption, the largest eruption generated in the Colorado River Extensional Corridor (CREC) of the southwestern United States. Within and immediately surrounding the caldera is a sequence of volcanics and intrusions ranging in age from ~19 to 17 Ma. These units offer a record of magmatic processes prior to, during, and immediately following the PST eruption. To investigate the thermal evolution of the magmatic center that produced the PST, we applied a combination of Ti-in-zircon thermometry, zircon saturation thermometry, and high-precision U–Pb CA–TIMS zircon dating to representative pre- and post-supereruption volcanic and intrusive units from the caldera and its environs. Similar to intracaldera PST zircons, zircons from a pre-PST trachytic lava (19 Ma) and a post-PST caldera intrusion (18.8 Ma) yield exceptionally high-Ti concentrations (most >20 ppm, some up to nearly 60 ppm), corresponding to calculated temperatures that exceed 900 °C. In these units, Ti-in-zircon temperatures typically surpass zircon saturation temperatures (ZSTs), suggesting the entrainment of zircon that had grown in hotter environments within the magmatic system. Titanium concentrations in younger volcanic and intrusive units (~18.7–17.5 Ma) decline through time, corresponding to an average cooling rate of 10?3.5 °C/year. The ~200 k.y. thermal peak evident at Silver Creek caldera is spatially limited: elsewhere in the Miocene record of the northern CREC, Ti-in-zircon concentrations and ZSTs are much lower, suggesting that felsic magmas were generally substantially cooler. 相似文献
17.
Fractional abundances of stratospheric negative ions are for the first time explicitly reported. The measurements made by balloon-borne ion mass spectrometers also rely on recent studies of electric field induced collisional dissociation of negative cluster ions conducted at our laboratory. These indicate that the negative ion composition measurements around 36 km conducted by our group do not suffer from any significant dissociation. The new composition data support ion identifications NO3?(HNO3)b and HSO4?(H2SO4)c(HNO3)d and the underlying ion reactions propo previously. Moreover, it is found that HSO4?(H2SO4)g-ions appear to be particularly stable and that H2SO4-association is very fast. Implications of the ion composition data for ion processes are discussed. 相似文献
18.
Sound from an airborne source travels to a receiver beneath the sea surface via a geometric path that is most simply described using ray theory, where the atmosphere and the sea are assumed to be isospeed sound propagation media separated by a planar surface (the air-sea interface). This theoretical approach leads to the development of a time-frequency model for the signal received by a single underwater acoustic sensor and a time-delay model for the signals received by a pair of spatially separated underwater acoustic sensors. The validity of these models is verified using spatially averaged experimental data recorded from a linear array of hydrophones during various transits of a turboprop aircraft. The same approach is used to solve the inverse time-frequency problem, that is, estimation of the aircraft's speed, altitude, and propeller blade rate given the observed variation with time of the instantaneous frequency of the received signal. Similarly, the inverse time-delay problem is considered whereby the speed and altitude of the aircraft are estimated using the differential time-of-arrival information from each of two adjacent pairs of widely spaced hydrophones (with one hydrophone being common to each pair). It is found that the solutions to each of the inverse problems provide reliable estimates of the speed and altitude of the aircraft, with the inverse time-frequency method also providing an estimate that closely matches the actual propeller blade rate 相似文献
19.
20.
A.A. Viggiano F. Arnold D.W. Fahey F.C. Fehsenfeld E.E. Ferguson 《Planetary and Space Science》1982,30(5):499-506
The results of a rocket-borne mass spectrometer measurement indicate that large concentrations of negative ions exist above the bottom of the atmospheric atomic oxygen layer. A large majority of these ions have a mass greater than 100 amu. In addition, an ion at mass 76 was observed with concentrations too large to be CO4?. In order to explain these features, a number of reactions involving silicon oxide negative ions have been measured in a flowing afterglow system. The ion SiO3? is produced by reaction of O3?, and CO3?, with SiO. The SiO3? ion is extremely stable and does not react measurably with NO, NO2, CO, CO2, O3 or O. Since meteoroid ablation produces a large silicon input into the atmosphere, it appears possible that the ions observed at mass 76 may be SiO3?. Possible production mechanisms for this ion as well as the heavy ions are discussed. 相似文献