福建莆田忠门半岛全新世砂砾岩的成因与古环境意义     

刘健  李绍全 《海洋科学》1998,22(3):54-57

论述了福建省莆田县忠门乡苦鹅头村东南海岸一套全新世含生物碎屑的砂、砾岩的沉积特征、沉积环境及其对海平面变化的反映。砂、砾岩层可划分成上、下两段,具有不同的成因。下段（０￣２．６ｍ）为海滩沉积,形成于中全新世高海平面时期。上段（２．６￣８ｍ）是全新世晚期（约３￣２ｋａ ＢＰ）的风沙沉积,内部夹有两个弱土壤化层,表明在风沙沉积作用过程中有过两次短暂的气候波动。  相似文献   

Nd and Sr isotopic variations in Chinese eolian deposits during the past 8 Ma: Implications for provenance change   总被引：3，自引：0，他引：3  

Jimin Sun 《Earth and Planetary Science Letters》2005,240(2):454-466

A record of changes in Nd and Sr isotopic composition of the eolian deposits from the central Loess Plateau has been determined for the past 8 Ma. The isotopic records of the silicate fraction of the Quaternary and Tertiary eolian deposits allow interpreting the interplay between the Sr isotopic variations in the eolian deposits and the late Cenozoic tectonic and climatic changes. The results indicate that the temporal variations of Nd and Sr isotopes show remarkable changes around the beginning of the Quaternary. The lower values of the ¹⁴³Nd/¹⁴⁴Nd and the decreasing trend of the ⁸⁷Sr/⁸⁶Sr ratios after 2.58 Ma ago are attributed to the additions of relatively younger crust materials in response to the climatic cooling and the late Cenozoic uplift induced glacial grinding in the high orogenic belts in central Asia. In this context, the substantial changes in climate and tectonics have modified dust sources significantly, and the Quaternary loess forming processes are preferentially sampling relatively younger and high relief crust materials than that of the Tertiary Red Clay.  相似文献   

Permeability upscaling of fault zones in the Aztec Sandstone,Valley of Fire State Park,Nevada, with a focus on slip surfaces and slip bands     

Ramil Ahmadov  Atilla Aydin  Mohammad Karimi-Fard  Louis J. Durlofsky 《Hydrogeology Journal》2007,15(7):1239-1250

The effect of open and filled slip surfaces on the upscaled permeability of two fault zones with 6 and 14 m strike-slip in an eolian Aztec Sandstone, Nevada, USA is evaluated. Each fault zone is composed of several fault components: a fault core, bounded by filled through-going slip surfaces referred to as slip bands, and a surrounding damage zone that contains joints and deformation bands. Slip band geometry, composition, and petrophysical properties are characterized. Measurements and modeling show that slip band permeabilities can vary over 12 orders of magnitude depending on the degree of fill within the slip bands. The slip bands along with other fault zone components are represented in finite volume numerical calculations and the impact of various slip-band representations on upscaled fault zone permeability is tested. The results show 2 orders of magnitude variation in upscaled fault zone permeability in the fault-normal direction and a factor of 2 variation in the fault-parallel direction. The numerical results presented here are compared to the earlier numerical results in which structured Cartesian grids were used for the numerical simulations, and are in qualitative agreement with earlier calculations but use about a factor of 250–400 fewer numerical cells.  相似文献   

Loess accumulation and soil formation in central kansas,United States,during the past 400 000 years   总被引：1，自引：0，他引：1  

Zhao-Dong Feng  W. C. Johnson  D. R. Sprowl  Yanchou Lu 《地球表面变化过程与地形》1994,19(1):55-67

Based on interpolation of thermoluminescence dates and the mean accumulation rate of 0.034 mm yr^?1, four cycles of pedogenic CaCO₃ accumulation are found within the Loveland Loess: 415–325 ka, 325–250 ka, 250–195 ka and 195–95 ka. The four CaCO₃ peaks correspond chronologically to marine oxygen isotope stages 11, 9, 7 and 5, respectively. The early Wisconsin (95–70 ka) was characterized by sand dune activity. The reddish pedocomplex was formed from 70 to 35 ka under relatively warm and moist climatic conditions with a very slow rate of silt accumulation (0·016 mm yr^?1). The Gilman Canyon pedocomplex, enriched in organic matter and dated at 35–20 ka, was formed under a strong physical weathering regime and a relatively high rate of silt accumulation (0·15 mm yr^?1), indicating a windy, relatively moist, probably cool environment. It developed when the Laurentide ice sheet was advancing and dust content in Greenland ice core was low. The Peoria Loess was accumulated at a rate of 0·3 mm yr^?1 in central Kansas under cold dry conditions when the ice sheet fluctuated around its maximum position and the dust content in the Greenland ice core was the highest. Even the warm substage around 13 ka has some corresponding evidence in the central Great Plains. The well-developed Brady Soil, dated at 10·5–8·5 ka, indicates that the early Holocene was the optimal time for soil development since 20 ka. The poorly weathered Bignell Loess might have been deposited during the Altithermal Period from 8·5 to 6 ka.  相似文献   

Field evaluation of some sand transport models     

Neil H. Berg 《地球表面变化过程与地形》1983,8(2):101-114

Fluorescent tracer procedures, originally developed for research on fluvial sediment movement, were used to monitor the movement of three commercially purchased sands in a natural dune environment. Results were compared with estimates of transport rates from three theoretical models. Estimates from models by Bagnold (1941) and Hsu (1971) were larger by as much as one order of magnitude than the rates observed in the tracer study. The model of A. A. Kadib (1965) provided closer correspondence to observed transport rates for medium sand (mean diam. 0.653 mm) but underestimated rates for coarse sand (mean diam. 0.992 mm).  相似文献   

查格勒布鲁剖面—晚更新世以来东亚季风进退的地层记录   总被引：3，自引：1，他引：3  

高全洲  董光荣 《中国沙漠》1996,16(2):112-119

本文着重分析了查格勒布鲁剖面沉积物的粒度特征和孢粉组合特征，结合（１４）Ｃ测年、古冰缘现象和沉积物化学元素的ＳｉＯ２／Ａｌ２Ｏ３分子比值变化规律指出，晚更新世以来巴丹吉林沙漠南缘地区的气候条件随全球冰期气候的波动亦经历了由晚更新世早期的相对温湿阶段、晚更新世晚期尤其是末次盛冰期的干冷阶段向全新世温暖期的演化过程。东亚夏季风尾阎在晚更新世早期到达甚至越过本区影响到拐子湖一带，晚更新世晚期本区受冬季风的控制，全新世以来东亚夏季风尾闾又向本区推进，并于全新世大暖期对本区造成明显影响。  相似文献   

长乐东南和海坛岛风沙资源特征及其开发利用     

张文开 《台湾海峡》1997,16(1):100-105

长乐东部和海坛是福建省的主要风沙分布区，风成沙是重要的自然资源。本文分析了风沙地貌类型及其分布特征、风成沙成分等，探讨了风沙资源的开发利用和保护等问题。  相似文献   

A short-lived aeolian event during the Early Holocene in southeastern Norway     

《Quaternary Geochronology》2015

The Starmoen dune field is part of a larger aeolian system in the Jømna and Glomma river valleys in southeastern Norway. It is believed to have formed just after the last deglaciation in the area, but no absolute ages have been available to support this. Here, we present a set of quartz optically stimulated luminescence (OSL) ages from the aeolian sediments and the underlying glacifluvial deposits. The results show that the main dune-building phase was a short-lived event ∼10 ka ago, likely with a duration less than a few hundred years. This suggests a rapid stabilisation of an initially unstable environment in newly deglaciated terrain. A much younger event with limited and surficial reworking of sand is dated to 770 ± 110 years ago, and the modern age of an active dune provide additional OSL quality control. Age overestimation is found for glacifluvial sediments, probably due to incomplete bleaching as indicated by e.g. scattered dose distributions from small aliquots. OSL measurements were conducted using coarse quartz grains (180–250 m), which show a dominance of a fast signal component.  相似文献   

Identification of Eolian Sandstone in Cretaceous Uraniferous Sandstone in Ordos Basin,ChinaEI北大核心CSCD     

Qiao D.  Kuang H.  Liu Y.  Peng N.  Liu Y.  Xu H.  Cui L.  Li Z. 《大地构造与成矿学》2020,(4):648-666

Uraniferous rocks in the lower part of Cretaceous Luohe Formation of Well XX located at the southwestern Ordos Basin have been investigated through core logging, microscopic observation, scanning electron microscope and granularity analyses. The desert (lower part) and ephemeralalluvial (upper part) sedimentary facies, composed of dune, interdune, sandsheet, wadi, and channel, bank subfacies are identified. The lower part of the Luohe Formation consists of red, yellow, and grayish green coarse- to fine-grained sandstone. The sandstone lacks cement and matrix, and quartz grains as the main mineral component are commonly clean and bright, with a small amount of debris (sedimentary debris) and feldspar (microcline and striped feldspar), indicating a high composition maturity. These particles are mostly medium-fine, sub-angular to sub-rounded, and the grain size distribution is mainly concentrated between 2.2ϕ and 3ϕ. The grain size curve shows that the sandstone is mainly composed of jumping transport components, with a small amount of suspended transport components, which means that the sandstone is well sorted and structurally high mature. Large scale and high angle cross bedding, parallel bedding, and wavy bedding are common, and tongue shaped grain flow with upward or downward pinching, wind ripple strata with reverse grain sequence, pin stripe lamination with dark color can be identified in the layer. Under scanning electron microscope, a series of dished and crescent impact craters, pockmarks, chemical dissolution and precipitation, desert paint, and other phenomena are identified on the surface of sandstone particles. Comparing with the characteristics of typical fluvial sandstone and eolian sandstone, the uraniferous sandstone in the lower part of the Luohe Formation in the southwestern Ordos Basin is of typical eolian sandstone. The eolian uraniferous sandstone is a new type of uranium-bearing sandstone reservoirs in the world, and this discovery expands the exploration space and potential for uranium deposits in North China, and provides new direction for further exploration of sandstone type uranium deposits. Further research is still underway. © 2020, Science Press. All right reserved.  相似文献   

辽东湾晚更新世末期陆相沉积石英砂表面的微结构   总被引：1，自引：1，他引：1  

徐文强  黄求获 《海洋科学》1994,18(2):51-56

通过对辽东湾柱状样下部沉积物石英砂表面微结构的观察，研究，得出其犋具有明显的风成陆相沉积环境。  相似文献