Preface     

George H. Denton  & Brenda L. Hall 《Geografiska Annaler: Series A, Physical Geography》2000,82(2-3):139-141

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The Wasatch Environmental Observatory: A mountain to urban research network in the semi-arid western US     

Jennifer J. Follstad Shah  Ryan Bares  Brenda B. Bowen  Gabriel J. Bowen  David R. Bowling  David P. Eiriksson  Benjamin Fasoli  Richard P. Fiorella  Anna Gannet Hallar  Sarah J. Hinners  John D. Horel  Alexander A. Jacques  Logan R. Jamison  John C. Lin  Daniel L. Mendoza  Logan E. Mitchell  Diane E. Pataki  Sarah McKenzie Skiles  Rose M. Smith  Margaret A. Wolf  Paul D. Brooks 《水文研究》2021,35(9):e14352

The 2085 km² Jordan River Basin, and its seven sub-catchments draining the Central Wasatch Range immediately east of Salt Lake City, UT, are home to an array of hydrologic, atmospheric, climatic and chemical research infrastructure that collectively forms the Wasatch Environmental Observatory (WEO). WEO is geographically nested within a wildland to urban land-use gradient and built upon a strong foundation of over a century of discharge and climate records. A 2200 m gradient in elevation results in variable precipitation, temperature and vegetation patterns. Soil and subsurface structure reflect systematic variation in geology from granitic, intrusive to mixed sedimentary clastic across headwater catchments, all draining to the alluvial or colluvial sediments of the former Lake Bonneville. Winter snowfall and spring snowmelt control annual hydroclimate, rapid population growth dominates geographic change in lower elevations and urban gas and particle emissions contribute to episodes of severe air pollution in this closed-basin. Long-term hydroclimate observations across this diverse landscape provide the foundation for an expanding network of infrastructure in both montane and urban landscapes. Current infrastructure supports both basic and applied research in atmospheric chemistry, biogeochemistry, climate, ecology, hydrology, meteorology, resource management and urban redesign that is augmented through strong partnerships with cooperating agencies. These features allow WEO to serve as a unique natural laboratory for addressing research questions facing seasonally snow-covered, semi-arid regions in a rapidly changing world and an excellent facility for providing student education and research training.  相似文献   

Soil formation in Phobjikha Valley,Central Bhutan with special regard to the redistribution of loessic sediments     

T. Caspari  R. Bäumler  C. Norbu  K. Tshering  I. Baillie 《Journal of Asian Earth Sciences》2009,34(3):403-417

Soil development and landscape evolution were studied in the basin-shaped Phobjikha Valley at 2900–3200 m a.s.l., to the west of the Black Mountain Range, West Central Bhutan. The local environmental setting with strong along-valley winds, frequent freeze–thaw cycles, extensive dry periods and sparse vegetation cover seems to encourage the generation and short-distance transport of silt-sized particles. The effects of this process are evidenced in the smooth valley morphology and in the nature of the examined pedons. Their involvement in continuing redistribution of local sediments is reflected by a homogeneous silty-clayey and stone-free texture, varying profile depths, buried topsoils and weakly developed recent A horizons. In protected locations, in situ weathering of metamorphic parent materials results in alu-andic features with bulk densities <0.9 g cm^?3, (Al_o + ½Fe_o) > 2%, and phosphate retention >95%. Dominance by Al-hydroxy interlayered clay minerals and large amounts of well-crystallised iron oxides indicate an advanced stage of weathering. In areas of preferred eolian deposition, argic and ferralic features emerge, with clay contents of up to 60% and surface areas of >50 m² g^?1. Under forest, umbric horizons can develop. CEC_eff is below 10 cmol_c kg^?1 at all sites. Cluster and factor analyses of soil chemical and physical parameters confirm the redistribution of local sediments as a dominant factor behind the measured variables. No clear indication of glacial activities in the area was found, whereas the massive silty sediments in the lower parts of most profiles, the presence of debris slopes, and the asymmetric cross sections of the side valleys suggest periglacial conditions. Buried topsoils dated at about 2000 conventional ¹⁴C years BP indicate a weakening or absence of sediment influx under wetter conditions towards the end of the Holocene climate optimum. Charcoal on top of paleosols suggests that human activities of deforestation, grazing and arable agriculture may have contributed to the reactivation of local sediment redistribution until today.  相似文献   

Using a historical aerial photograph analysis to inform trout habitat restoration efforts     

Marshall B. Baillie  Nira L. Salant  John C. Schmidt 《地球表面变化过程与地形》2011,36(12):1693-1702

Restoration of the upper Strawberry River included bank stabilization techniques because it was assumed that excessive bank erosion was degrading spawning habitat for Bonneville cutthroat trout (BCT). Using a long‐term aerial photograph record, the historical range of variability in bank erosion rates and channel geometry was determined, and this information was used to assess present‐day conditions and the rationale for restoration. Relative to historical variability, the channel planform was relatively stable and bank erosion rates were the lowest recorded in the post‐disturbance era. Although a historical loss of riparian vegetation coincided with a shift to a wider and more sinuous channel, lateral migration rates declined and the channel narrowed as riparian cover increased in the decades before restoration, indicating a process of natural recovery. Furthermore, it was found that the percentage of fine sediment in the streambed before restoration was insufficient to affect BCT spawning success. Together these results suggest that bank erosion and fine sediment did not affect the quality of spawning habitat or the abundance of BCT on the upper Strawberry River. The results highlight how a historical analysis can be used to identify the sources of habitat degradation and inform the selection of restoration goals and strategies. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A new hammer-driven freeze corer   总被引：1，自引：0，他引：1  

Brenda M. Miskimmin  P. Jefferson Curtis  David W. Schindler  Nestor Lafaut 《Journal of Paleolimnology》1996,15(3):265-269

A shortcoming of freeze corers has been the inability to collect long cores in stiff sediments. We describe a hammerdriven freeze corer that collects undisturbed sediment cores up to 1.3 m in length in stiff or soft lake sediments. The corer was tested in prairie, montane and alpine lakes of western Canada. For these stiff sediments, conventional (gravity-only) freeze coring methods collected cores ranging from 25–59 cm compared with 100–124 cm for our hammer-driven device. The maximum length of cores could exceed 1.3 m if a longer core barrel was constructed.  相似文献   

A precisely‐dated lake‐level rise marked by diatomite formation in northeastern Ireland     

G. M. Plunkett  N. J. Whitehouse  V. A. Hall  D. M. Brown  M. G. L. Baillie 《第四纪科学杂志》2004,19(1):3-7

The intercorrelation of palaeoclimate events from various studies is often hindered by a lack of precise chronological control. Tephra isochrons can overcome this problem by providing direct site linkages. This paper outlines a study of Holocene peat and diatomite deposits that accumulated within the floodplain of Lough Neagh, Northern Ireland. The Icelandic Hekla 4 tephra has been identified at the base of diatomite deposits at a number of sites and provides firm dating evidence for a widespread flooding event in the area at ca. 2300 BC . The evidence is consistent with other studies in Ireland and elsewhere for increased wetness at this time. The results demonstrate that the terrestrial deposits around Lough Neagh contain an important record of Holocene lake‐level change. Dendrochronological evidence from the Lough Neagh area provides additional information about lake‐level fluctuations over the past two millennia. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Problems with identifying the ‘8200‐year cold event’ in terrestrial records of the Atlantic seaboard: a case study from Dooagh,Achill Island,Ireland     

Katie Head  Chris S. M. Turney  Jon R. Pilcher  J. G. Palmer  M. G. L. Baillie 《第四纪科学杂志》2007,22(1):65-75

The Northern Hemisphere cooling event 8200 years ago is believed to represent the last known major freshwater pulse into the North Atlantic as a result of the final collapse of the North American Laurentide ice sheet. This pulse of water is generally believed to have occurred independently of orbital variations and provides an analogue for predicted increases in high‐latitude precipitation and ice melt as a result of anthropogenically driven future climate change. The precise timing, duration and magnitude of this event, however, are uncertain, with suggestions that the 100‐yr meltwater cooling formed part of a longer‐term cold period in the early Holocene. Here we undertook a multiproxy, high‐resolution investigation of a peat sequence at Dooagh, Achill Island, on the west coast of Ireland, to determine whether the 8200‐year cold event impacted upon the terrestrial vegetation immediately ‘downwind’ of the proposed changes in the North Atlantic. We find clear evidence for an oscillation in the early Holocene using various measures of pollen, indicating a disruption in the vegetation leading to a grassland‐dominated landscape, most probably driven by changes in precipitation rather than temperature. Radiocarbon dating was extremely problematic, however, with bulk peat samples systematically too young for the North Atlantic event, suggesting significant contamination from downward root penetration. The sustained disruption to vegetation over hundreds of years at Dooagh indicates the landscape was impacted by a long‐term cooling event in the early Holocene, and not the single century length 8200‐year meltwater event proposed in many other records in the North Atlantic region. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Geological features indicative of processes related to the hematite formation in Meridiani Planum and Aram Chaos, Mars: a comparison with diagenetic hematite deposits in southern Utah, USA     

Jens Ormö  Goro Komatsu  Brenda Beitler 《Icarus》2004,171(2):295-316

In order to understand the formation of the few but large, hematite deposits on Mars, comparisons are often made with terrestrial hematite occurrences. In southern Utah, hematite concretions have formed within continental sandstones and are exposed as extensive weathered-out beds. The hematite deposits are linked to geological and geomorphological features such as knobs, buttes, bleached beds, fractures and rings. These terrestrial features are visible in aerial and satellite images, which enables a comparison with similar features occurring extensively in the martian hematite-rich areas. The combination of processes involved in the movement and precipitation of iron in southern Utah can provide new insights in the context of the hematite formation on Mars. Here we present a mapping of the analogue geological and geomorphological features in parts of Meridiani Planum and Aram Chaos. Based on mapping comparisons with the Utah occurrences, we present models for the formation of the martian analogues, as well as a model for iron transport and precipitation on Mars. Following the Utah model, high albedo layers and rings in the mapped area on Mars are due to removal or lack of iron, and precipitation of secondary diagenetic minerals as fluids moved up along fractures and permeable materials. Hematite was precipitated intraformationally where the fluid transporting the reduced iron met oxidizing conditions. Our study shows that certain geological/geomorphological features can be linked to the hematite formation on Mars and that pH differences could suffice for the transport of the iron from an orthopyroxene volcanoclastic source rock. The presence of organic compounds can enhance the iron mobilization and precipitation processes. Continued studies will focus on possible influence of biological activity and/or methane in the formation of the hematite concretions in Utah and on Mars.  相似文献   

Geochemistry and Provenance of Springs in a Baja California Sur Mountain Catchment     

Jory C. Lerback  Brenda B. Bowen  C. E. Humphrey  Diego. P. Fernandez  Jeremiah A. Bernau  Shane J. Macfarlan  Eric Schniter  J. J. Garcia 《Ground water》2022,60(2):295-308

Fractured rock aquifers cover much of Earth's surface and are important mountain sites for groundwater recharge but are poorly understood. To investigate groundwater systematics of a fractured-dominated aquifer in Baja California Sur, Mexico, we examined the spatial patterns of aquifer recharge and connectivity using the geochemistry of springs. We evaluate a range of geochemical data within the context of two endmember hypotheses describing spatial recharge patterns and fracture connectivity. Hypothesis 1 is that the aquifer system is segmented, and springs are fed by local recharge. Hypothesis 2 is that the aquifer system is well connected, with dominant recharge occurring in the higher elevations. The study site is a small <15 km² catchment. Thirty-four distinct springs and two wells were identified in the study area, and 24 of these sites were sampled for geochemical analyses along an elevation gradient and canyon transect. These analyses included major ion composition, trace element and strontium isotopes, δ¹⁸O and δ²H isotopes, radiocarbon, and tritium. δ¹⁸O and δ²H isotopes suggest that the precipitation feeding the groundwater system has at least two distinct sources. Carbon isotopes showed a change along the canyon transect, suggesting that shorter flowpaths feed springs in the top of the transect, and longer flowpaths discharge near the bottom. Geochemical interpretations support a combination of the two proposed hypotheses. Understanding of the connectivity and provenance of these springs is significant as they are the primary source of water for the communities that inhabit this region and may be impacted by changes in recharge and use.  相似文献   

Late Pleistocene snowline fluctuations at Nevado Coropuna (15°S), southern Peruvian Andes     

Gordon R.M. Bromley  Brenda L. Hall  Kurt M. Rademaker  Claire E. Todd  Adina E. Racovteanu 《第四纪科学杂志》2011,26(3):305-317

Deposits preserved on peaks in the southern Peruvian Andes are evidence for past glacial fluctuations and, therefore, serve as a record of both the timing and magnitude of past climate change. Moraines corresponding to the last major expansion of ice on Nevado Coropuna date to 20‐25 ka, during the last glacial maximum. We reconstructed the snowline at Coropuna for this period using a combined geomorphic‐numeric approach to provide a first‐order estimate of the magnitude of late‐Pleistocene climate change. Our reconstructions show that snowline was approximately 550‐770 m lower during the last glacial maximum than during the late Holocene maximum, which ended in the 19^th century, and ～750 m lower than today. While these values are similar to data from nearby Nevado Solimana, reconstructions from the neighbouring peak of Nevado Firura reveal a smaller snowline depression, suggesting the glacial response to climate forcing in the tropics is strongly influenced by non‐climatic factors. These data constitute some of the first directly dated palaeo‐snowline data from the arid tropics and suggest that the magnitude of the last glaciation in at least parts of the tropical Andes was similar to late‐Pleistocene events at higher latitudes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献