Late Pleistocene Glaciations in the Northwestern Sierra Nevada, California     

L. Allan James  Jon Harbor  Derek Fabel  Dennis Dahms  David Elmore 《Quaternary Research》2002,57(3):409

Pleistocene fluvial landforms and riparian ecosystems in central California responded to climate changes in the Sierra Nevada, yet the glacial history of the western Sierra remains largely unknown. Three glacial stages in the northwestern Sierra Nevada are documented by field mapping and cosmogenic radionuclide surface-exposure (CRSE) ages. Two CRSE ages of erratic boulders on an isolated till above Bear Valley provide a limiting minimum age of 76,400±3800 ¹⁰Be yr. Another boulder age provides a limiting minimum age of 48,800±3200 ¹⁰Be yr for a broad-crested moraine ridge within Bear Valley. Three CRSE ages producing an average age of 18,600±1180 yr were drawn from two boulders near a sharp-crested bouldery lateral moraine that represents an extensive Tioga glaciation in Bear Valley. Nine CRSE ages from striated bedrock along a steep valley transect average 14,100±1500 yr and suggest rapid late-glacial ice retreat from lower Fordyce Canyon with no subsequent extensive glaciations. These ages are generally consistent with glacial and pluvial records in east-central California and Nevada.  相似文献   

Borehole drainage and its implications for the investigation of glacier hydrology: experiences from Haut Glacier d'Arolla,Switzerland     

Shulamit Gordon  Martin Sharp  Bryn Hubbard  Ian Willis  Chris Smart  Luke Copland  Jon Harbor  Bradley Ketterling 《水文研究》2001,15(5):797-813

Studies of glacier hydrology rely increasingly on measurements made in boreholes as a basis for reconstructing the character and behaviour of subglacial drainage systems. In temperate glaciers, in which boreholes remain open to the atmosphere following drilling, the interpretation of such data may be complicated by supraglacial or englacial water flows to and from boreholes. We report on a suite of techniques used to identify borehole water sources and to reconstruct patterns of water circulation within boreholes at Haut Glacier d'Arolla, Switzerland. Results are used to define a number of borehole ‘drainage’ types. Examples of each drainage type are presented, along with the manner in which they influence interpretations of borehole water‐levels, borehole water‐quality data, and borehole dye traces. The analysis indicates that a full understanding of possible borehole drainage modes is required for the correct interpretation of many borehole observations, and that those observations provide an accurate indication of subglacial conditions only under relatively restricted circumstances. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

The role of hydrology in annual organic carbon loads and terrestrial organic matter export from a midwestern agricultural watershed   总被引：1，自引：0，他引：1  

Brent J. Dalzell  Timothy R. Filley  Jon M. Harbor 《Geochimica et cosmochimica acta》2007,71(6):1448-1462

Defining the control that hydrology exerts on organic carbon (OC) export at the watershed scale is important for understanding how the source and quantity of OC in streams and rivers is influenced by climate change or by landscape drainage. To this end, molecular (lignin phenol), stable carbon isotope, and dissolved organic carbon (DOC) data were collected over a range of flow conditions to examine the influence of hydrology on annual OC export from an 850 km² Midwestern United States agricultural watershed located in west central Indiana. In years 2002 and 2003, modeled annual DOC loads were 19.5 and 14.1 kg ha⁻¹yr⁻¹, while 71% and 85%, respectively, of the total annual OC was exported in flow events occurring during less than 20% of that time. These results highlight the importance of short-duration, high-discharge events (common in smaller watersheds) in controlling annual OC export. Based on reported increases in annual stream discharge coupled with current estimates of DOC export, annual DOC loads in this watershed may have increased by up to 40% over the past 50 years. Molecular (lignin phenol) characterization of quantity and relative degradation state of terrestrial OC shows as much temporal variability of lignin parameters (in high molecular weight dissolved organic carbon) in this one watershed as that demonstrated in previously published studies of dissolved organic matter in the Mississippi and Amazon Rivers. These results suggest that hydrologic variability is at least as important in determining the nature and extent of OC export as geographic variability. Moreover, molecular and bulk stable carbon isotope data from high molecular weight dissolved organic carbon and colloidal organic carbon showed that increased stream flow from the study watershed was responsible for increased export of agriculturally derived OC. When considered in the context of results from other studies that show the importance of flood events and in-stream processing of terrestrial organic carbon, our results show how hydrologic variability in smaller watersheds can reflect landscape-scale carbon dynamics in ways that cannot necessarily be measured at the outlets of large rivers due to multiple source signals and attenuated hydrology.  相似文献   

南京汤山洞穴石笋稳定同位素指示的气候与环境意义   总被引：16，自引：1，他引：15  

汪永进  许汉奎 《地质学报》2000,74(4):333-338

对南京汤山葫芦洞南壁钙板上一支长８２ｍｍ石笋进行了高精度热电离质谱（ＴＩＭＳ）定年及氧碳同位素分析。结果表明,该支短石笋生长时段长达３００ｋａ左或（距今４６３～１５９ｋａ）,其底部年龄进一步证实南京直立人生存时代早于４５０ｋａＢＰ。δ＾１３Ｃ值在ＭＩＳ６／７界线上的显著漂移揭示了一次土壤侵蚀事件,结束了洞穴文化层的堆积历史。  相似文献   

The Gas Resources Assessment Expert System of the Songliao Basin     

LONG Shengxiang  WANG ChuanResearch Institute of Petroleum Geology  China National StarPetroleum Corporation CNSPC  Xueyuan R  Beijing  LI Yuzhan Exploration Department  CNSPC  Xueyuan R  Beijing 《《地质学报》英文版》2000,74(3):666-673

The gas resources assessment expert system is one of the advanced methods for appraising oil and gas resources. The establishment of a knowledge base is the focal task in developing the expert system. This paper presents a summary of the mechanism and the major controlling factors in the formation of gas pools in the southeast uplift of the Songliao basin. Then an appropriate assessment model is established for trapping the gas resources and a knowledge base built in the expert system to realize the model. By using the expert system to appraise the gas-bearing probability of 25 major traps of the Quantou and Denglouku Formations in the Shiwu-Dehui area, the authors have proved that the expert system is suitable for appraising traps in the Songliao basin and similar basins.  相似文献   

喜马拉雅山佩枯岗日冰川地貌的年代学、平衡线高度和气候研究   总被引：8，自引：6，他引：2  

刘耕年  Li Yingkui  陈艺鑫  张梅  李川川  孔屏  Harbor J.  Caffee M.W. 《冰川冻土》2011,33(5):959-970

喜马拉雅山珠穆朗玛峰-希夏邦马峰地区是青藏高原南部现代冰川集中发育区之一,古冰川遗迹亦十分丰富,是研究第四纪青藏高原冰川形成和演化的关键区,一直备受地貌和第四纪环境研究者的关注.应用原地宇宙核素10Be暴露年龄测试技术,对采自希夏邦马峰西北佩枯岗日拉曲谷地冰碛垄上的冰川漂砾进行年代学研究;结合冰川地貌分析方法,对古冰川...  相似文献   

Semial ophiolite veins of United Arab Emirates―A fluid inclusions study     

Mohamed El Tokhi  Abdulla Musallam 《中国地球化学学报》2011,(3)

Calcite and quartz veins in the gabbroic and dunite rocks of the Semial ophiolite (UAE) were selected for fluid inclusion analysis. The inclusions contain both aqueous low-salinity and hydrocarbon-dominated fluids. Mi-crothermometry data indicate that the aqueous fluids contain 0.22 to 1.45 equivalent wt% NaCl and occasionally contain traces of hydrocarbons. Homogenization to liquid occurred between 91 and 152℃. Modeling based on these fluid inclusion observations indicates that the trapping conditions of t...  相似文献   

准周期振荡(QPO)天体GX5-1的双分支谱的唯象分析     

尤峻汉  陆埮  冯珑珑  晏明 《中国天文和天体物理学报》1990,(4)

本文对小质量X射线双星的准周期振荡的差频模型做了修正和补充。修正的要点是:要考虑柱吸积过程中的粘滞阻尼。由此即可成功地解释QPO天体GX5-1的双分支谱特性。  相似文献   

波阻抗反演正则参数估计   总被引：24，自引：0，他引：24       下载免费PDF全文

张宏兵  尚作萍  杨长春  段秋梁 《地球物理学报》2005,48(1):181-188

为了解决用正则化方法能够将波阻抗反演的病态问题转为良态问题,通过统计方法合理地选择正则参数的初值,在反演过程中用极大似然（ML）方法实时进行正则参数值估计,提高反演收敛速度,改善反演结果。同时,在具体反演中将正则化方法与快速模拟退火算法相结合,充分发挥正则参数作用,可以获得全局最优解,取得了好的实际应用效果。  相似文献   

A Climatic Sequence Stratigraphic Model in the Terrestrial Lacustrine Basin:A Case Study of Green River Formation,Uinta Basin,USA     

Ronald STEEL 《《地质学报》英文版》2009,83(1)

In recent years,with the development of terrestrial sequence stratigraphy,more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers.Under the guidance of the theory of sequence stratigraphy,the findings of this paper indicate that climate is a major factor controlling the formation of the fourth-order sequence,based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta...  相似文献