Hydrogeological implications of paleo-fluvial architecture for the Paskapoo Formation, SW Alberta, Canada: a stochastic analysis     

Erick R. Burns  Laurence R. Bentley  Masaki Hayashi  Stephen E. Grasby  Anthony P. Hamblin  Derald G. Smith  Paul R. J. Wozniak 《Hydrogeology Journal》2010,18(6):1375-1390

Fluvial systems tend to deposit sediment in well-defined relational geometries and in vertically and laterally repeating patterns. These sedimentary deposits are preserved to varying degrees depending on how much the fluvial system reworks the deposits. The Paskapoo bedrock aquifer system in southern Alberta, Canada, was deposited in a foreland depositional basin during uplift of the Rocky Mountains, and both the geomorphic model and field evidence indicate that the upper 100 m of the local aquifer system contains well-preserved, highly connected paleo-channels and associated overbank deposits. In order to evaluate the value of different types of data, a simplified stochastic-numerical groundwater flow model was developed to examine the sensitivity of results to model parameters. Parameters examined include: fraction of the formation made up of channel sands; meander and sinuosity factors; width-to-depth ratios of preserved channels; and crevasse splay conductivity. In all cases examined, the system exhibited anisotropic behavior with the along-channel flow direction being the most permeable and the vertical direction being least permeable. In general, the strongest control on the resulting effective anisotropic hydraulic conductivities was channel fraction, but geometric factors that control between-channel connectivity (e.g., channel sinuosity) had an appreciable effect on the across-channel flow direction effective permeability.  相似文献   

Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora)     

James O. Farlow  Shoji Hayashi  Glenn J. Tattersall 《Swiss Journal of Geoscience》2010,103(2):173-185

X-ray computed tomography and petrographic thin sectioning were used to study internal features of the plates of the thyreophoran dinosaur Stegosaurus and the osteoderms of Alligator. Infrared thermographic imaging of basking caimans was used to examine possible differential blood flow to osteoderms and other parts of the skin. Multiple large openings in the Stegosaurus plate base lead to a linear, mesiodistally oriented vestibule, which in turn apically sends off multiply branching “pipes”. The pipes are best developed in the basal half of the plate, and communicate with cancellous regions (some of which presumably were vascular spaces) throughout the plate interior. Some internal vascular features also connect with vascular pits and grooves on the plate surface. Alligator osteoderms show a similar internal vascularity. In crocodylians, the osteoderms serve as armor and help to stiffen the back for terrestrial locomotion, but their vascularity enables them to be used as sources of calcium for egg shelling, as sites of lactate sequestration, and possibly for heat exchange with the external environment, as suggested by our infrared thermographic imaging of basking caimans. Thyreophoran osteoderms presumably had multiple functions as well. In Stegosaurus the potential thermoregulatory role of the plates may have been greater than in other thyreophorans, by virtue of their extensive external and internal vascularity, their large size, thin cross-sections above the plate base, dorsal position, and alternating arrangement.  相似文献   

Subsurface thermal environment and groundwater flow around Tokyo Bay,Japan     

Vuthy Monyrath  Yasuo Sakura  Akinobu Miyakoshi  Takeshi Hayashi 《Environmental Earth Sciences》2010,60(5):923-932

Previous studies and borehole temperature measurements suggest that subsurface temperature distribution on the west side of Tokyo Bay (from Tokyo to Yokohama) is higher than that of the east side (Chiba side). To understand the groundwater flow and other factors which may contribute to the subsurface temperature discrepancy such as geological setting in the study area, groundwater temperature profiles were measured in 119 boreholes around the Tokyo Bay from 2002 to 2007. The data were analyzed and compared with previous studies. Horizontal distribution of subsurface temperature at the depths of −50 and −100 m was made to show the distribution of thermal regime. A cross-section across the bay of Tokyo was made to see the isothermal lines and distribution of hydraulic heads in a vertical perspective. These results show that the highest subsurface temperature zone is in the Tokyo area, along the river valley. Subsurface temperature at the depth of 50- and 100-m below sea level in the western part of the bay is comparatively higher than its eastern side at the same elevation and distance from the bay. This fact suggests that there is a regional groundwater flow system in the area and it is strongly affected by the geological structure, particularly buried valley systems of the bay during the Paleo-Tokyo River and the topographical driving force which is the result of the different elevation of recharge areas. Groundwater discharge is concentrated along the buried valley of Paleo-Tokyo River.  相似文献   

Observations of Coherent Turbulence Structures in the Near-Neutral Atmospheric Boundary Layer   总被引：1，自引：1，他引：0  

Mitsuaki Horiguchi  Taiichi Hayashi  Hiroyuki Hashiguchi  Yoshiki Ito  Hiromasa Ueda 《Boundary-Layer Meteorology》2010,136(1):25-44

Turbulence structures of high Reynolds number flow in the near-neutral atmospheric boundary layer (ABL) are investigated based on observations at Shionomisaki and Shigaraki, Japan. A Doppler sodar measured the vertical profiles of winds in the ABL. Using the integral wavelet transform for the time series of surface wind data, the pattern of a descending high-speed structure with large vertical extent (from the surface to more than 200-m level) is depicted from the Doppler sodar data. Essentially this structure is a specific type of coherent structure that has been previously shown in experiments on turbulent boundary-layer flows. Large-scale high-speed structures in the ABL are extracted using a long time scale (240 s) for the wavelet transform. The non-dimensional interval of time between structures is evaluated as 3.0–6.2 in most cases. These structures make a large contribution to downward momentum transfer in the surface layer. Quadrant analyses of the turbulent motion measured by the sonic anemometer (20-m height) suggest that the sweep motion (high-speed downward motion) plays a substantial role in the downward momentum transfer. In general, the contribution of sweep motions to the momentum flux is nearly equal to that of ejection motions (low-speed upward motions). This contribution of sweep motions is related to the large-scale high-speed structures.  相似文献   

Role of tonalite-trodhjemite-granite (TTG) crust subduction on the mechanism of supercontinent breakup   总被引：1，自引：0，他引：1  

Hiroki Senshu  Shigenori Maruyama  Shuji Rino  M. Santosh 《Gondwana Research》2009,15(3-4):433-442

The tonalite-trondhjemite-granite (TTG) crust has been considered to be buoyant and hence impossible to be subducted into the deep mantle. However, recent studies on the juvenile arc in the western Pacific region indicate that immature island arcs subduct into the deep mantle in most cases, except in the case of parallel arc collision. Moreover, sediment trapped subduction and tectonic erosion are also common. This has important implications in evaluating the role of TTG crust in the deep mantle and probably on the bottom of the mantle. Because the TTG crust is enriched in K, U and Th, ca. 20 times more than that of CI chondrite, the accumulated TTG on the Core Mantle Boundary (CMB) would have played a critical role to initiate plumes or superplumes radiating from the thermal boundary layer, particularly after 2.0 Ga, related to the origin of superplume-supercontinent cycle. This is because selective subduction of oceanic lithosphere including sediment-trapped subduction, tectonic erosion and arc- and microcontinent-subduction proceeded under the supercontinent before the final amalgamation ca. 200-300 million years after the formation of the nuclei. We speculate the mechanism of superplume evolution through the subduction of TTG-crust and propose that this process might have played a dominant role in supercontinent breakup.  相似文献   

Granite subduction: Arc subduction, tectonic erosion and sediment subduction   总被引：10，自引：5，他引：5  

Shinji Yamamoto  Hiroki Senshu  Shuji Rino  Soichi Omori  Shigenori Maruyama 《Gondwana Research》2009,15(3-4):443-453

Continental growth has been episodic, reflecting the episodic nature of mantle dynamics as well as surface dynamics of the Earth, the net result of which is exhibited by the present mantle with two huge reservoirs of TTG rocks, one on the surface continents and the other on the D″ layer on the Core-Mantle Boundary (CMB). During the early half of the Earth history, the felsic continental crust on the surface which formed in an intra-oceanic environment has mostly been subducted into the deep mantle, except in the rare case of parallel arc collision. The growth history of continental crust shows that with its simultaneous formation, a considerable amount must have also been subducted. Such ongoing subduction processes can be seen in the western Pacific region, through tectonic erosion, arc subduction, and sediment-trapped subduction.  相似文献   

Micro-FTIR spectroscopic signatures of Bacterial lipids in Proterozoic microfossils     

Motoko Igisu  Yuichiro Ueno  Mie Shimojima  Satoru Nakashima  Stanley M. Awramik  Hiroyuki Ohta  Shigenori Maruyama   《Precambrian Research》2009,173(1-4):19

Precambrian microbial fossils show carbonaceous cellular structure, which often resemble in shape and size cyanobacteria and other prokaryotes. Morphological taxonomy of these minute, simple, and more or less degraded fossils is, however, often not enough to determine their precise phylogenetic positions. Here we report the results of micro-FTIR spectroscopic analyses of well-preserved microfossils in 850 Ma and 1900 Ma stromatolites, together with those of 8 species of extant prokaryotes and 5 of eukaryotes for comparison. These Proterozoic fossils have low CH₃/CH₂ absorbance ratios (R_3/2 < 0.5) of aliphatic CH moieties, suggesting selective preservation of long, straight, aliphatic carbon chains probably derived from bacterial membrane lipids. All the observed R_3/2 values of coccoids, filaments and amorphous organic matter resemble lipid fractions of extant Bacteria including cyanobacteria, but not Archaea. The results indicate that Proterozoic microfossils belong to Bacteria, which is consistent with the cyanobacterial origin inferred from morphology. Moreover, the R_3/2 value of fossilized cell would reflect chemical composition of its precursor membrane lipid, thus could be a useful new tracer for distinguishing Archaea, Bacteria and possibly Eucarya for fossilized and extant microorganisms.  相似文献   

Millennial-scale vegetation changes during the last 40,000 yr based on a pollen record from Lake Biwa, Japan     

Ryoma Hayashi  Hikaru Takahara  Keiji Takemura 《Quaternary Research》2010,74(1):91-202

A high-resolution pollen record covering the last 40,000 yr (BIW95-4) from Lake Biwa, western Japan, shows regional vegetation responses to millennial-scale climate changes. From 40 to 30 ka, Cryptomeria japonica was dominant around the lake among pinaceous conifers and deciduous broad-leaved trees. During this period, fluctuations of C.japonica are correlated with Dansgaard-Oeschger (D-O) cycles recognized from the anhysteretic remanent magnetization (ARM) record. Increases in the abundance of this taxon may have been caused by wetter summer conditions influenced by the East Asian monsoon or increased snowfall on the Sea of Japan side of the Japanese archipelago. Between 29 and 14 ka, pinaceous conifer forests mainly composed of Pinus subgenus Haploxylon, Tsuga, and Picea trees developed. At approximately 23 ka, Picea trees increased in abundance as ARM values decreased. This expansion of Picea trees has been correlated with Heinrich event (HE) 2 in the North Atlantic. At about 14 ka, the distribution of broad-leaved forest (mainly composed of deciduous oaks) began to expand after D-O 1. Evidence of significant vegetation change related to the abrupt Younger Dryas cooling event has not been found.  相似文献   

Land-use comparison of depression-focussed groundwater recharge in the Canadian prairies     

Laura R. Morgan  Masaki Hayashi  Edwin E. Cey 《水文研究》2021,35(9):e14379

In the cold semiarid Canadian prairies, groundwater recharge is focussed under numerous topographic depressions, in which snowmelt runoff converges. Agricultural land uses on the uplands surrounding the depressions affect snow accumulation, snowmelt infiltration, evapotranspiration (ET) and soil moisture dynamics, thereby influencing snowmelt runoff and depression-focussed recharge. The objective of this study is to compare the differences in hydrological processes under two common land uses in the Canadian prairies, namely grazed grass and annual crop, and examine how they affect groundwater recharge. A short-term (3 years) paired catchment study was used for detailed observation of hydrological processes in two depressions, supplemented by a longer-term (17 years) data set covering a larger scale to quantify the differences in snowmelt runoff between the two land uses. Compared to the grazed grassland, the cropland had a shorter and more intense period of ET, and root water uptake restricted to the shallower (top 0–80 cm) soil zone. The amount of snowmelt runoff was greater in the grazed grassland primarily due to a higher amount of snow accumulation, which was dictated by differences in topography. This finding was contrary to previous studies in the Canadian prairies that indicated substantially smaller snowmelt runoff in ungrazed grassland, but was consistent with the larger-scale remote sensing results, which showed only a marginal difference between grazed grasslands and croplands. Groundwater recharge rates were estimated using the chloride mass balance method for the present condition using “modern” pore water containing tritium. The rates were similar between the grazed grassland and croplands, implying similarity in snowmelt runoff characteristics. These results suggest that groundwater recharge will continue to be focussed under depressions in the future, though the amount and seasonality of recharge may be influenced by warmer winters.  相似文献   

Influence of a rock glacier spring on the stream energy budget and cold‐water refuge in an alpine stream          下载免费PDF全文

Jordan S. Harrington  Masaki Hayashi  Barret L. Kurylyk 《水文研究》2017,31(26):4719-4733

The thermal regimes of alpine streams remain understudied and have important implications for cold‐water fish habitat, which is expected to decline due to climatic warming. Previous research has focused on the effects of distributed energy fluxes and meltwater from snowpacks and glaciers on the temperature of mountain streams. This study presents the effects of the groundwater spring discharge from an inactive rock glacier containing little ground ice on the temperature of an alpine stream. Rock glaciers are coarse blocky landforms that are ubiquitous in alpine environments and typically exhibit low groundwater discharge temperatures and resilience to climatic warming. Water temperature data indicate that the rock glacier spring cools the stream by an average of 3 °C during July and August and reduces maximum daily temperatures by an average of 5 °C during the peak temperature period of the first two weeks in August, producing a cold‐water refuge downstream of the spring. The distributed stream surface and streambed energy fluxes are calculated for the reach along the toe of the rock glacier, and solar radiation dominates the distributed stream energy budget. The lateral advective heat flux generated by the rock glacier spring is compared to the distributed energy fluxes over the study reach, and the spring advective heat flux is the dominant control on stream temperature at the reach scale. This study highlights the potential for coarse blocky landforms to generate climatically resilient cold‐water refuges in alpine streams.  相似文献