Pyrolysis of modern wetland sediment: extracting climate records from fens in the Uinta Mountains and Fish Lake Plateau,Utah, USA     

Samuel M. Hudson  Samuel A. Hillam  Joel Barker  Stephen T. Nelson  Kevin A. Rey 《Boreas: An International Journal of Quaternary Research》2019,48(3):810-824

Rock‐Eval pyrolysis provides a quick, relatively inexpensive means of characterizing organic‐rich strata, and has been used for decades to understand global petroleum systems. Although designed to characterize ancient kerogens, pyrolysis is increasingly being used to understand Holocene systems as well. The ability of this technique to distinguish between types of preserved organic matter is useful in characterizing climatic evolution, particularly in systems sensitive to climatic fluctuation such as isolated fens and bogs. Cores collected from the Tokewanna and Garden Basin Cattail fens in central/eastern Utah exhibit variability of organic source, with the mixture of terrestrial and algal sources varying through time, as shown through the hydrogen index (HI) and oxygen index pyrolysis parameters. A sediment core was collected at each fen, and 176 samples were taken from the cores at 6‐cm intervals. Total organic carbon (TOC) for all samples ranges from 1.3 to 44.2%, with an average of 18.2% TOC. Samples range from 84 to 687 HI, equivalent to Type I (lacustrine algal) to Type III (terrestrial) organic material (OM). Variability in HI response represents mixing of the two OM sources, and the relative amount of aqueous organic input can be estimated through time based on age‐calibrated HI curves at the two sites. The balance of organic input serves as an accurate, high‐resolution proxy for climate, and calibration with palynological data near both sites confirms patterns shown by pyrolysis, showing the utility of this method in quickly, affordably and accurately characterizing Holocene sediments for use in understanding palaeoclimate.  相似文献   

Comparison of ground-based and Viking Orbiter measurements of Martian water vapor: Variability of the seasonal cycle     

Bruce M. Jakosky  Edwin S. Barker 《Icarus》1984,57(3):322-334

Earth-based observations of Mars atmospheric water vapor, made from McDonald Observatory, are presented for the 1975–1976, 1977–1978, and 1983 apparitions. Comparisons are made with near-simultaneous spacecraft measurements made from the Viking Orbiter MarsAtmospheric Water Detection experiment during 1976–1978 and with previous Earth-based measurements (made since 1964). Differences occur between the behavior in the different years, and may be related to the Mars climate. Measurements during the southern summer in 1969 indicate a factor of three times as much water as is present at this same season in other years.This difference may have resulted from the sublimation of water from the south polar residual cap upon removal of most or all of the CO₂ ice present; sublimation of all the CO₂ ice during some years could be a result of a greater thermal load being placed on the cap due to the presence of differing amounts of atmospheric dust. If substantiated, the water vapor variability will turn out to be a very sensitive indicator of yearly variability in the Martian climate.  相似文献   

Organic matter: size fraction relationships for recent sediments from the Orinoco Delta,Venezuela     

Joseph I. Nwachukwu  Colin Barker 《Marine and Petroleum Geology》1985,2(3):202-209

Fifteen recent sediment samples from the offshore Orinoco Delta, Venezuela, were separated by sieving and pipette analysis into seven size fractions ranging from 4ø to 10ø, in 1 ø units. Total organic carbon was determined for each size fraction and the organic matter characterized by pyrolysis and pyrolysis-gas chromatography. The sediments average 0.98% organic matter with somewhat higher values nearshore. Nearshore sediments also had higher organic contents in the coarsest fractions and a decrease in organic matter from coarse to fine sediment fractions. Sediments from further offshore generally show the highest organic contents in the finer fractions. Pyrolysis showed a low bitumen content and confirmed that the kerogen was dominantly terrestrial and gas prone. The observed trends were attributed to sorting of organic matter by its physical characteristics, with the denser, coarse-grained material settling out nearshore and the Finer-grained material being carried further from shore and settling out with finer-grained sediments.  相似文献   

Forbidden Ca ii in the Sun unmasked by way of Venus     

Ronald A. Schorn  Andrew T. Young  Edwin S. Barker 《Solar physics》1975,43(1):9-14

Eleven high-dispersion spectra of Venus, taken with blue Doppler shifts have enabled us to unmask the 7323.88 Å forbidden line of Ca ii from terrestrial absorption. We obtain an equivalent width of 7.4±0.4 mÅ for this line in integrated sunlight. Our value of W _λ is smaller than previous values and much more accurate. The HSRA solar model gives a solar calcium abundance of A _Ca = 6.21.  相似文献   

Semiperiodic variations in CO₂ abundance on Venus     

Edwin S. Barker  Michael A. Perry 《Icarus》1975,25(2):282-295

Photoelectric spectral scans of the P branch of the 8689 Å CO₂ band on Venus were made using the 107-inch coude scanner during seven observing periods in the past 2 years. The relative CO₂ line strength was determined for each scan, then normalized to remove the spatial variations leaving only temporal variations.The 4-day periodicity in the relative CO₂ line strength noted by Young et al. (1973) is not unique; we do confirm their 4-day periodicity in August 1973. Four other observing periods rule out a 4-day periodicity.A definite North-South asymmetry in the relative CO₂ line strength is noted during 1973, in most cases with the same periodicity present in both hemispheres. When the slit positions are referred to the equator of Venus, particularly near inferior conjunction, the large asymmetrics between the slit positions can be explained by a greater CO₂ line strength over the polar regions and weaker over the equatorial latitudes. The amplitude of variation of each position on the crescent is much greater near inferior conjunction either because we are sampling a smaller area on the planet or because the upper atmospheric abundance is more sensitive to the mechanism causing the variation in the smaller regions sampled at inferior conjunction.Simultaneous H₂O measurementsduring several of the observing runs indicate a lack of correlation in the relative CO₂ line strengths and the H₂O abundance.  相似文献   

Volcanic particles in agriculture and gardening          下载免费PDF全文

Valentin R. Troll  Juan Carlos Carracedo  Beatrice Jägerup  Michael Streng  Abigail K. Barker  Frances M. Deegan  Francisco Perez‐Torrado  Alejandro Rodriguez‐Gonzalez  Harri Geiger 《Geology Today》2017,33(4):148-154

Volcanic pyroclasts of small size, such as lapilli and small pumice stones, are widely used in agriculture, gardening, and for pot plants as natural inorganic mulch. The technique of using pyroclasts to enhance topsoil stems from the eighteenth century, and specifically from the ad 1730–1736 eruption on Lanzarote. Critical observations on plant development during and after the eruption showed that the vegetation died when buried under a thick layer of lapilli, but grew vigorously when covered thinly. While the agriculture of Lanzarote was restricted to cereals before the eruption, it diversified to many kinds of fruit and vegetables afterwards, including the production of the famous Malvasía wines in the Canaries. The population of Lanzarote doubled in the years after the eruption, from about 5000 in 1730 to near 10 000 in 1768, predominantly as a result of the higher agricultural productivity. This outcome led to widespread use of lapilli and pumice fragments throughout the islands and eventually the rest of the globe. Lapilli and pumice provide vesicle space for moisture to be retained longer within the planting soil, which can create an environment for micro‐bacteria to thrive in. Through this route, nutrients from volcanic matter are transported into the surrounding soil where they become available to plant life. The detailed processes that operate within the pyroclasts are less well understood, such as the breakdown of nutrients from the rock matrix and transport into the soil by biological action. Further studies promise significant potential to optimize future agricultural efforts, particularly in otherwise arid areas of the globe.  相似文献   

The economics of avoiding dangerous climate change. An editorial essay on The Stern Review   总被引：2，自引：0，他引：2  

Terry Barker 《Climatic change》2008,89(3-4):173-194

The problem of avoiding dangerous climate change requires analysis from many disciplines. Mainstream economic thinking about the problem has shifted with the Stern Review from a single-discipline focus on cost-benefit analysis to a new inter-disciplinary and multi-disciplinary risk analysis, already evident in the IPCC Third Assessment Report. This shift is more evidence of the failure of the traditional, equilibrium approach in general to provide an adequate understanding of observed behaviour, either at the micro or macro scale. The economics of the Stern Review has been accepted by governments and the public as mainstream economic thinking on climate change, when in some critical respects it represents a radical departure from the traditional treatment. The conclusions regarding economic policy for climate change have shifted from “do little, later” to “take strong action urgently, before it is too late”. This editorial sets out four issues of critical importance to the new conclusions about avoiding dangerous climate change, each of which have been either ignored by the traditional literature or treated in a misleading way that discounts the insights from other disciplines: the complexity of the global energy-economy system (including the poverty and sustainability aspects of development), the ethics of intergenerational equity, the understanding from engineering and history about path dependence and induced technological change, and finally the politics of climate policy.  相似文献   

Seismic Source Characteristics of Soviet Peaceful Nuclear Explosions   总被引：1，自引：0，他引：1  

J. R. Murphy  I. O. Kitov  B. W. Barker  D. D. Sultanov 《Pure and Applied Geophysics》2001,158(11):2077-2101

—?During the period 1965 to 1988, the former Soviet Union (FSU) conducted over 120 peaceful nuclear explosions (PNE) at locations widely dispersed throughout the territories of the FSU. These explosions sample a much wider range of source conditions than do the historical explosions at the known nuclear test sites and, therefore, seismic data recorded from these PNE tests provide a unique resource for use in deriving improved quantitative bounds on the ranges of seismic signal characteristics which may require consideration in global monitoring of the Comprehensive Test-Ban Treaty (CTBT). In this paper we summarize the results of a detailed statistical analysis of broadband seismic data recorded at the Borovoye Geophysical Observatory from 21 of these PNE tests at regional distances extending from about 7 to 19 degrees, as well as the results of theoretical waveform simulation analyses of near-regional (Δ?相似文献   

A Rubidium-Strontium study of the Twilight Gneiss,West Needle Mountains,Colorado     

Fred Barker  Zell E. Peterman  Robert A. Hildreth 《Contributions to Mineralogy and Petrology》1969,23(4):271-282

The Precambrian trondhjemitic Twilight Gneiss (Twilight Granite of Cross and Howe, 1905b) of the West Needle Mountains, southwestern Colorado, and its interlayered amphibolite and metarhyodacite yield a Rb-Sr isochron of 1,805±35 m.y. A low initial Sr⁸⁷/Sr⁸⁶ ratio of 0.7015 implies that metamorphism of these rocks to amphibolite facies took place soon after their emplacement. The mild metamorphism of Uncompahgran age, prior to 1,460 m.y. ago, and Laramide volcanism did not affect the Rb-Sr system in the Twilight. Rb contents of 26.5 to 108 ppm, Sr contents of 114 to 251 ppm, and K₂O percentages of 1.23 to 3.64 in the Twilight Gneiss, in conjunction with high K/Rb ratios and the low initial ratio of Sr⁸⁷/Sr⁸⁶, lend support to geologic data that suggest the Twilight originated as volcanic or hypabyssal igneous rocks in a basaltic volcanic pile.Publication authorized by the Director, U.S. Geological Survey.  相似文献   

A Semipassive Nutrient Injection Scheme for Enhanced In Situ Bioremediation   总被引：1，自引：0，他引：1  

J. F. Devlin  J. F. Barker 《Ground water》1994,32(3):374-380

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