Sedgwick and his trilobite     

Ken McNamara 《Geology Today》2014,30(4):142-146

Standing on guard at the entrance to the Palaeozoic section of the University of Cambridge's Sedgwick Museum is a bronze statue of the man after whom the museum was named—the 7th Woodwardian Professor, the Reverend Adam Sedgwick. In one hand he holds his trusty geological hammer, in the other is a rock. Sedgwick, the man who unraveled many of the mysteries of the early Palaeozoic rocks of Wales, looks as if he has just cracked a piece of rock off an outcrop. Yet, rather incongruously, he is swathed in his academic gown—our man is clearly both the consummate field geologist and the academic.  相似文献   

Non-ENSO interannual rainfall variability in central Chile during austral winter     

Aldo Montecinos  Michael V. Kurgansky  Cristian Muñoz  Ken Takahashi 《Theoretical and Applied Climatology》2011,106(3-4):557-568

The first principal component (PC1) of seasonal rainfall anomalies in central Chile during winter (June–August) is used to analyze the circulation anomalies related to wet and dry conditions, when near-normal or neutral SST anomalies are observed in the equatorial Pacific, i.e., during non-ENSO conditions. Eight wet and eight dry winter seasons were defined as the upper and lower terciles of PC1 for 24 non-ENSO winters in the period 1958–2000. Unlike the single process attributed to ENSO, during non-ENSO winter seasons, there are several sources triggering or modifying the propagation of the stationary waves that impact the rainfall regime in central Chile. Unfortunately, the multiple processes that seem to be involved in the modulation of the interannual rainfall variability in central Chile, as seen in this work, limit the predictability of rainfall during non-ENSO conditions.  相似文献   

Evaluation of the use of paleotsunami deposits to reconstruct inundation distance and runup heights associated with prehistoric inundation events,Crescent City,southern Cascadia margin     

Curt D. Peterson  Gary A. Carver  Ken M. Cruikshank  Hans F. Abramson  Carolyn E. Garrison‐Laney  Lori A. Dengler 《地球表面变化过程与地形》2011,36(7):967-980

Historic‐ and prehistoric‐tsunami sand deposits are used to independently establish runup records for tsunami hazard mitigation and modeled runup verification in Crescent City, California, located in the southern Cascadia Subduction Zone. Inundation from historic (1964) farfield tsunami (~5–6 m runup height) left sand sheet deposits (100–200 m width) in wetlands located behind a low beach ridge [3–4 m elevation of the National Geodetic Vertical Datum of 1988 (NAVD88)]. The most landward flooding lines (4·5–5 m elevation) in high‐gradient alluvial wetlands exceed the 1964 sand sheet records of inundation by 1–2 m in elevation. The most landward flooding in low‐gradient alluvial wetlands exceed the corresponding sand sheet record of inundation distance by 1000 m. Nevertheless, the sand sheet record is an important proxy for high‐velocity inundation. Sand sheet deposition from the 1964 historic tsunami closely corresponds to the landward extent of large debris transport and structural damage in the Crescent City waterfront. The sand sheet deposits provide a proxy for maximum hazard or ‘kill zone’ in the study area. Six paleotsunami sand sheets (0·3–3 ka) are recorded in the back‐ridge marshes in Crescent City, yielding a ~450 year mean recurrence interval for nearfield Cascadia tsunami. Two paleotsunami sand deposit records, likely correlated to Cascadia ruptures between 1·0 and 1·5 ka, are traced to 1·2 km distance and 9–10 m elevation, as adjusted for paleo‐sea level. The paleotsunami sand deposits demonstrate at least twice the runup height, and four times the inundation distance of the farfield 1964 tsunami sand sheet in the same marsh system. The preserved paleotsunami deposits in Crescent City are compared to the most landward flooding, as modeled by other investigators from a predicted Cascadia (~ Mw 9) rupture. The short geologic record (~1·5 ka) yields slightly lower runup records than those predicted for the modeled Mw 9 rupture scenario in the same marsh, but it generally verifies predicted maximum tsunami runup for use in the planning of emergency response and rapid evacuation. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Climate and vegetation in Hokkaido, northern Japan, since the LGM: Pollen records from core GH02-1030 off Tokachi in the northwestern Pacific     

Yaeko Igarashi  Masanobu Yamamoto  Ken Ikehara 《Journal of Asian Earth Sciences》2011,40(6):78-1110

Vegetation and climate since the LGM in eastern Hokkaido were investigated based on a pollen record from marine core GH02-1030 from off Tokachi in the northwestern Pacific. We also examined pollen spectra in surface samples from Sakhalin to compare and understand the climatic conditions of Hokkaido during the last glacial period. Vegetation in the Tokachi region in the LGM (22–17 ka) was an open boreal forest dominated by Picea and Larix. During the last deglaciation (17–10 ka), vegetation was characterized by abundant Betula. In the Kenbuchi Basin, central Hokkaido, a remarkable increase of Larix and Pinus occurred in the LGM and the last deglaciation, which was assigned as the “Kenbuchi Stadial.” Comparison of climatic data between the core GH02-1030 and that of Kenbuchi Basin demonstrates that variations in temperature and precipitation were larger in inland Hokkaido than in the maritime area of the Pacific coast. During the LGM in the Tokachi region, the August mean temperature was about 5 °C lower, and annual precipitation was about 40% lower than today. In the Kenbuchi Basin, central Hokkaido, the August mean temperature was about 8 °C lower, and annual precipitation was half that of today. During the last deglaciation, August mean temperatures were about 3 °C lower, and annual precipitation was about 30% lower than today in the Tokachi region. In the Kenbuchi Basin, August mean temperatures were about 5–8 °C lower, and annual precipitation was about 40–60% lower than today. Cold ocean water and a strengthened summer monsoon after 15 ka may have resulted in the formation of advection fogs, reduced summer temperatures, and a decrease in the seasonal temperature difference in the Tokachi district, which established favorable maritime conditions for Betula forests.  相似文献   

Tidal flushing time of marine fish culture zones in Hong Kong     

毛劲乔  黄子文  李行伟  蔡景华 《中国海洋工程》2011,25(4):625-643

Accurate determination of flushing time is crucial for maintaining sustainable production in fish culture zones(FCZs),as it represents the physical self-purification capability via tidal exchange with clean water in the outer sea.However,owing to the temporal and spatial complexity of the coastal flushing process,existing methods for determining flushing time may not be generally applicable.In this paper,a systematic method for determining the flushing time in FCZs is presented,in which bathymetry,runoff,tidal range and stratification are properly accounted for.We determine the flushing time via numerical tracer experiments,using robust 3D hydrodynamic and mass transport models.For FCZs located in sheltered and land-locked tidal inlets,the system boundary can be naturally defined at the connection with the open sea.For FCZs located in open waters,hydrodynamic tracking is first used to assess the extent of tidal excursion and thus delimit the initial boundary between clean water and polluted water.This general method is applied to all designated marine FCZs in Hong Kong for both the dry and wet seasons,including 20 sheltered FCZs(in semi-enclosed waters of Tolo Harbour,Mirs Bay,and Port Shelter) and 6 FCZs in open waters.Our results show that flushing time is the longest in inner Port Shelter(about 40 days in dry season),and the shortest for the FCZs in open waters(less than one week in dry season).In addition,the flushing time in dry season is commonly longer than that in wet season:20%~40% for most well-sheltered FCZs;2.6~4 times for the others.Our results indicate a positive correlation between the flushing time and distance to open boundary,supporting the view that the flushing time of a FCZ is closely related to its location.This study provides a solid basis for mariculture management such as the determination of carrying capacity of FCZs.  相似文献   

Shear zone vs folding origin for spiral inclusion trails in the Canton Schist   总被引：1，自引：0，他引：1  

Aaron Stallard  Ken Hickey 《Journal of Structural Geology》2001,23(12):1272

The three-dimensional geometry of spiral inclusion trails from the Canton Schist were measured to determine whether the spirals were a product of porphyroblast rotation within a shear zone, or porphyroblast growth during a series of overprinting fold events. The spiral inclusion trails are composed of three separate, sub-planar inclusion trail surfaces occupying texturally distinct parts of the porphyroblasts. These surfaces are correlated across a >10 km² area using textural criteria and relative timing. Measured patterns of inclusion trail orientation and asymmetry suggest they did not form by porphyroblast rotation within a non-coaxial shear zone. Rather, the porphyroblasts grew during three successive overprinting fold events (F₂–F₄), and the spiral inclusion trails represent the accumulated curvature associated with folding of successive axial plane foliations. The data show that spiral garnets are not peculiar to shear zones, and can form by overprinting crenulations and folds. This is consistent with the common occurrence of spiral garnets in multiply-deformed, regionally metamorphosed fold belts.  相似文献   

Soils of the world (wall chart), P. Lof,Elsevier, 1987. Price: US $15.50 or dfl. 45.00. ISBN 0–444–42575–6     

Ken Atkinson 《地球表面变化过程与地形》1989,14(4):363-364

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Book Review: “The Hydrogeology of Crystalline Basement Aquifers in Africa”     

Ken W. P. Howard 《Hydrogeology Journal》1992,1(4):49-50

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Towards a cleaner marine environment—European Community priorities for protection     

Ken Collins Mep 《Marine pollution bulletin》1994,29(6-12):641-643

The sea covers 70% of the Earth's surface and plays a fundamental role in the global ecosystem. In order to safeguard it effectively, action must be taken at many levels, by many users in many different areas. This paper will focus on the European Communities' policies for dealing with marine pollution. It discusses the case for joint action and describes how international, co-ordinated action can be most effectively enforced.

Protecting the marine environment by carefully regulating the activities of all users will require effective but realistic policies that can be monitored and enforced. It is necessary to consider shipping, the fishery industry, tourism and many other industries, to see where changes may be required. At the same time, it should be remembered that 80% of marine pollution derives from land-based sources. A holistic approach to environmental policy-making is therefore necessary in order to provide a cleaner marine environment.  相似文献   

Along-arc lateral variation of Rb−Sr and K−Ar ages of Cretaceous granitic rocks in Southwest Japan     

Takashi Nakajima  Teruo Shirahase  Ken Shibata 《Contributions to Mineralogy and Petrology》1990,104(4):381-389

Cretaceous granitic rocks were emplaced over a distance of 700 km along arc in Southwest Japan. Rb–Sr and K–Ar ages of a major group of these granitic rocks, with ilmenite series ore mineralogy, were examined. Rb–Sr whole rock ages of 92.8±4.0 Ma and Rb–Sr and K–Ar biotite ages of 80–88 Ma were obtained on one group of these granitic rocks from Kamo-Sera area of central Hiroshima Prefecture. The K–Ar ages of various minerals, combined with the Rb–Sr whole-rock age, give a smooth cooling curve, which suggests a 5 to 10 Ma time-lag between intrusion and cooling at 300° C for the Cretaceous granitic rocks. The Rb–Sr whole-rock and Rb–Sr/K–Ar biotite ages of these granitic rocks become younger eastward along the Southwest Japan arc, and the time-lag between the two systems remains constant at 5 to 10 Ma over the entire area. The along-arc age variation does not support the genetical relationship of the Cretaceous granitoids with steady-state subduction. The Cretaceous granitic province at the eastern margin of Eurasian continent was, at least partly, formed by an episodic event such as ridge subduction.  相似文献