A map of autumn precipitation for the third millennium BP in the Eastern Iberian Peninsula from charcoal carbon isotopes

Carbon isotope composition (δ¹³C) in tree-rings has become routinely used in palaeoclimatic research for the assessment of changes in plant water availability in seasonally dry climates. However, the distribution of long tree-ring records around the world is very limited. Alternatively, the original climate signal of wood δ¹³C is well preserved in fossil charcoal and, accordingly, charcoal δ¹³C can be used to quantify past changes in water availability (e.g. precipitation). We report a case study on spatial palaeoclimate reconstruction which aims to characterize the transition between Bronze and Iron Ages, the so-called Iron Age Cold Epoch (ca. 900–300 BCE), using charcoals of Quercus ilex/coccifera from a set of 11 contemporary archaeological sites of eastern Spain. Climatic inferences were obtained after calibrating a linear model predicting seasonal precipitation from δ¹³C of Q. ilex wood samples obtained across a rainfall gradient. The best regression model corresponded to September–December (autumn) precipitation (P_aut), in agreement with the fact that Q. ilex is able to exploit previous-year water reserves thanks to very effective water uptake. Subsequently, we estimated P_aut from the δ¹³C of fossil charcoal to infer spatial patterns in water availability. Overall, estimated past P_aut was about 19% higher (296 mm) than present-time values averaged across archaeological sites (249 mm). However, a clear geographic pattern of differences in precipitation could be observed in which the inner continental regions of eastern Spain were characterized by more humid conditions in the past, whereas the coastal strip of the Mediterranean Sea barely differed in past and present P_aut values. The quite uniform distribution of archaeological sites over eastern Spain allowed development of contour maps of absolute and relative (to present) past P_aut using gridded interpolation methods implemented in a GIS, highlighting the potential of this approach for reconstructing high-resolution spatial patterns of past climate.     

青海省查查香卡地区晚三叠世火山岩岩石学及其构造环境

通过对查查香卡地区晚三叠世火山岩岩石学特征、空间分布、形态、火山机构、火山岩与构造关系的研究,确定该套火山岩时代为晚三叠世。岩石地层单位为鄂拉山组,为一套陆相喷发火山岩,呈NW向展布于大海滩-都库隆瓦地区。以中-高钾、高钙、低钛为特征,属钙碱性系列。火山喷发活动由强到弱,岩性由中性向中酸性渐变,岩浆活动由喷发型向侵入型递进。表明岩石构造环境为陆内消减带火山岩中的造山区。是来自地壳下部的火山岩浆经分异结晶并在上涌过程中混入有上地壳物质而喷发形成。喷出时的大地构造环境为陆内造山环境,该火山岩最初可能形成于大陆边缘环境,由于A型俯冲构造活动,测区乃至鄂拉山地区产生一系列右旋走滑断裂带,受NW向右旋走滑断裂的影响,岩石孔隙加大,并出现强烈的热流活动,导致岩浆沿这些断裂带喷出地表。     

北天山巴音沟蛇绿岩形成时代的精确厘定及意义

应用SHRIMP方法对北天山巴音沟蛇绿岩中侵入辉长岩内的斜长花岗岩进行了锆石UPb年龄测定,表明斜长花岗岩形成于(324.8±7.1)Ma(2σ)。这一年龄精确反映了巴音沟蛇绿岩的形成时代于早石炭世晚期。巴音沟蛇绿岩形成于强烈大陆伸展作用导致的大陆裂谷向大洋裂谷转变的一种动力学环境,记录了由于裂谷作用强烈拉伸形成的初始洋壳,是晚古生代天山地区“红海型”洋盆的地质记录。     

Palaeomonsoon variability in the southern fringe of the Badain Jaran Desert,China, since 130 ka BP

Taking the Chagelebulu Stratigraphic Profile as a typical example, a comprehensive study has been conducted to elucidate the palaeoclimatic and geomorphic evolution patterns in the southern fringe of the Badain Jaran Desert, which were found to be complex and polycyclic in the past 130 ka. However, the fluctuating magnitude is not as remarkable as that in the eastern China sandy region. The shift in climate from interglacial to glacial and the uplift process of the Qinghai–Xizang Plateau are the two leading forces driving the evolution of the climate and desert landforms in this area. Seventeen cycles of cold, dry and warm, humid climatic stages were recognized in the Upper Pleistocene Series of the profile. The sharp uplift of the Qinghai–Xizang Plateau superimposed a cool and arid climatic trend in this area. As a result of the climatic changes, the desert in this area has undergone multiple stages of expansion and contraction since 130 ka bp . The middle Holocene Epoch and the early stage of the Late Pleistocene Period were the main periods when the sand dunes became stabilized, and the early and late phases of the Holocene Epoch and late phase of the Pleistocene Epoch were the main periods when the previously stabilized sand dunes became mobile. The late phase of the Pleistocene Epoch was the most mobile stage, when the aeolian sand activities formed the essential geomorphic pattern of the Badain Jaran Desert. Copyright © 2005 John Wiley & Sons, Ltd.     

Narrative warm/cold variations in continental western Europe, AD 708 -1426

An extended narrative dataset of the Medieval time AD 708-1426 in continental western Europe was set up. Some 30-year-moving mean seasonal temperature deviation series were reconstructed. A- warming trend occurred around AD 1200. During the warm stage, seasonal cycle might be weak due to frequent cool summers. Significant warm summer conditions did not occur until the late 14th century, when the annual temperature level began decreasing. The mean warm season temperature level during the late 14th to the early 15th century might be about 0.3°C higher than the present. It was suggested to cautiously comment on historical climates for different seasons.     

云南大理点苍山地区更新世晚期沉积地层的ESR测年研究

本文采用电于自旋共振（ESR）方法测定了云南点苍山地区更新世晚期沉积地层的形成年代。测年结果显示；（1）点苍山地区冰川沉积物的ESR年龄均小于140．35KaBP，说明该地区的第四纪冰川作用最早出现于中更新世晚期，主要发生于晚更新世；（2）点苍山西麓平坡附近最高一级基座阶地的堆积时代为184．3KaBP，证明西洱河阶地系列为中更新世以来的产物；（3）点苍山东侧白雀寺地区深3．7m处的褐红色地展形成的ESR年龄为12218KaBP，揭示出该地层形成于深海氧同位素5e阶段所代表的一个温热气候时期。     

Post-depositional realignment of magnetic grains and asymmetrical saw-tooth patterns of magnetization intensity

Recent paleomagnetic records suggest that the geomagnetic field intensity has a saw-tooth shape matching the succession of polarity intervals. An alternative hypothesis, that mechanisms linked to the acquisition of magnetization would induce similar saw-toothed records, has been tested by several simulations of post depositional reorientations of magnetic grains. Exponential functions used to date to describe post-depositional magnetization (pDRM) processes do not account for the combination of saw-toothed fluctuations and reasonable delays in the recording of the position of the reversals. At least half of the magnetization must be locked in within a few centimetres below the surface. If not, large delays, which are not observed in the data, are introduced in the stratigraphic positions of the reversals. In addition, the rest of the magnetization must be acquired over depths involving several tens of meters to duplicate a saw-toothed shape. These conclusions are reached with or without incorporating intensity variations across reversals. If the original signal is, in fact, asymmetrical then the pDRM must be very limited to remain coherent with the measurements, since the distortions and the offsets induced by the pDRM smoothing are considerably amplified. We conclude that simulations of saw-tooth patterns of relative paleointensity by pDRM processes have consequences that are difficult to reconcile with our present knowledge of the physical properties of deep-sea sediments. Above all, the hypothesis that the saw-tooth is an artifact of the magnetization acquisition process would have major implications for any sedimentary record of geomagnetic features.     

用磁性地层学方法讨论西域组的时代

通过对塔里木盆地及其周缘地区西域组砾岩的野外调查和磁性地层学研究，及相关层位的安山玄武岩同位素年龄测定等综合分析研究表明：西域组上段记录了松山负极性带下段， ２．５－１．６Ｍａ，上界大约位于奥尔都维正极性事件层位，年龄为１．６７－１．７６Ｍａ。上覆高阶地砾岩层及其下火山岩层年龄为１．４－１．６Ｍａ，西域组下段记录了高斯正极性     

通天河上游墩日含煤岩系地层时代的新认识

墩日含煤岩系时代原定为晚三叠世。该岩系的岩性、岩相、煤质、孢粉组合等诸多特征均反映了下侏罗统的沉积特点,故应将其厘定为早侏罗世。