Aeolian loess is one of the most widespread deposits on the land and records many kinds of information of paleoclimate changes. Currently, the studies of loess in Pakistan are rare, and the studies on the mechanism of magnetic susceptibility variation are still unavailable. In this study, the the rock magnetic parameters of the newly discovered loess-paleosol section (29 degrees 19'56 '' N, 71 degrees 42'65 '' E) in the Bahawalpur area of the Indus Plain of Pakistan were systematiclly measured. Combined with the grain size characteristics and the diffuse reflectance spectrum (DRS) , the mechanism of magnetic susceptibility variation was discussed. The results show that the main magnetic minerals in loess are magnetite, coupled with goethite and maghemite. And the magnetic domain particles in the magnetic minerals are Pseudo-single domain (PSD) and multi-domain (MD). Compared with the loess, the main magnetic minerals in paleosol are goethite, coupled with magnetite and paramagnetic minerals. This changing mechanism of the susceptibility is different from that of Chinese Loess Plateau (CLP). There is a possible threshold of magnetic susceptibility 12. 8 x 10(8) m(3) . kg(-1) in the study area, above which the main magnetic minerals are strongly magnetic minerals (magnetite and maghemite) ; below this value, the main magnetic minerals are weakly magnetic minerals (such as goethite). This transition of magnetic minerals may lead to a decrease in magnetic susceptibility. This study provides a new clue for further paleoclimatic research in Pakistan based on magnetic susceptibility in the future.

古土壤是重建古气候的重要手段,第四纪以前古土壤因受各种地质作用影响不易被识别.本研究以福建西部连城盆地晚白垩世红层 —— 冠豸山剖面为研究对象,通过野外观察、土壤微结构和地球化学元素迁移等方法识别和获得古土壤发育特征,并分析古土壤形成环境.冠豸山剖面共有10个薄层古土壤,主要为新成土和始成土两种类型,土壤发育较弱,没有明显的黏化层和钙结核层.沉积物颗粒和稀土元素分布特征显示剖面中含有一定的风积组分,风积物经短暂流水搬运再次沉积,形成沉积层理.红色碎屑颗粒在沉积之前已经历相当程度的风化,沉积后在干旱环境下成壤较弱,因此,对其古气候或古环境的认识需依据古土壤发育特征,这为研究类似红层提供了新的思路.

风成黄土是研究古气候变化的良好载体,在全球陆地分布广泛,而不同区域地理环境差异显著,其记录气候变化的机制亦有所不同.以色列南部黄土区地处亚热带沙漠边缘,为探究该区域黄土磁性特征及其对区域环境的响应机制,对内盖夫沙漠边缘黄土区进行野外考察并测试系统环境磁学及粒度参数.结果表明,Har Keren(HK)剖面中磁性矿物主要为碎屑磁铁矿和磁赤铁矿,磁性矿物含量较少,磁性颗粒主要为粗单畴(SD)和多畴(MD),磁性特征与中国西北干旱区黄土较为相似.HK剖面常温磁学参数整体变化范围较小,仅在剖面亚表层有所升高,可能是受现代成土作用影响.HK剖面中值粒径自底部至顶部呈减小趋势,但粒度整体偏粗,其频率分布曲线显示为正偏态,分选较差,反映出多种搬运方式的混合特征,与典型风成黄土有所差异.

The Cretaceous red beds in southeastern China are regarded as terrestrial elastic sediments, whose paleoenvironmental implication is still in debate. They are conventionally regarded as lacustrine-fluvial sediments in basin. In present study, the late Cretaceous paleoenvironment documented by red beds (Liancheng and Guanzhaishan section) in the western Fujian province were investigated based on environmental magnetism, grain size, geochemistry and paleosols.The results show that : (1) The red beds in the western Fujian, mostly in form of interbedded siltstone and sandstone with gravels, are dominated by fine silt particles with less clay and sand. The dominant magnetic carrier in red beds is hematite, which attributes to low values of magnetic susceptibility in the two sections. (2) The weathering degree, reflected by chemical index of alteration (CIA), is moderate as those formed in warm and humid climate. In addition, the rare earth elements (REE) of red beds show enriched light rare earth element (LREE), depleted heavy rare earth elements (HREE) , enrichment of Ce and negative Eu anomaly, which resembled that of average upper continental crust (UCC) , thus indicating thoroughly mixing sediments. (3) Although paleosols were recognized in the red beds, in particular GZS section, these paleosols were weakly developed with no evident of B horizon (e. g. Bk and Bt) in paleosol profile. The conflict between moderate chemical weathering degree and weak pedogensis infers that the red bed sediments had experienced to an extent chemical weathering in source area before deposition. After deposition, the red sediments were hardly chemically weathered. It should be noted that the red beds solely cannot indicate paleoenvironment, which must take paleosols into account. (4) The late cretaceous paleoenvironment in western Fujian was suspected to be arid and semiarid. The hematite in red beds were mainly derived from source area, indicating well-drained dry oxidizing environment, rather than aqueous condition. This work provides an alternative prospect in studying Cretaceous red beds.

The formation and transformation of magnetic minerals in soil indicate environmental change. The response mechanism of soil magnetism to environmental factors currently needs to be analyzed quantitatively. In present study, based on related research and field investigations, vertical zonal soil profiles with same parent material from Daiyun Mountain (subtropical area in south of Fujian province) were collected for environmental magnetism and diffuse reflectance spectrum (DRS) analysis. The results showed that magnetite and maghemite dominated the magnetic variation in the soil profiles. Lepidocrocite of secondary origin appeared in the soil at altitude of 1320 m. Given the influence of terrain was excluded, magnetic parameters indicated that SP magnetic domain dominated in the low-altitude soils, while the coarser SD magnetic domain dominated in the high-altitude soils. The results of diffuse reflection spectrum showed that hematite and goethite were sensitive to climate gradient changes in the study area. Hematite proportion decreased with the increase of altitude until completely disappeared at altitude of 1320 m, above which goethite and lepidocrocite became predominate. Semi-quantitative analysis of DRS characteristic peaks of goethite and hematite before and after heating suggested that the threshold of mean annual precipitation and mean annual temperature for hematite in subtropical mountains was likely 1900 mm and 13 degrees C , respectively, while meanwhile goethite and lepidocrocite increased with altitude. This study demonstrated that hematite, goethite and lepidocrocite were sensitive to climatic gradient and thus could be potentially used as important paleoenvironmental proxies in low-latitude regions.

黄土广布于全球各地,而不同区域黄土沉积特征存在差异,记录环境变化的机制亦有所不同.对以色列西南部Har Keren(简称HK)地区黄土状沉积剖面进行野外考察,发现其沉积特征与风积黄土较为相似.研究结果表明,HK剖面粒度特征虽表现出风成成因,但粒径整体偏粗且缺少细粉砂组分,说明剖面沉积物主要由近源风力搬运而来,并且在堆积过程中受坡积作用影响,沉积过程较为复杂.HK剖面稀土元素结果表现为右倾型特征,且轻稀土富集、重稀土亏损,Eu中度负异常,与典型风积黄土变化趋势基本一致,但∑REE明显偏低,可能与其物质来源、搬运模式和沉积环境的不同有关.HK剖面常量元素UCC标准化结果与腾格里沙漠边缘黄土分布曲线较为类似,化学蚀变指数(CIA)指示其处于中等化学风化程度,由于研究区气候干旱少雨,主要以物理风化为主,不可能发生较强的化学风化,认为其CIA异常偏高可能与源岩区的化学风化结果有关,由于搬运来的沉积物质中碱金属及碱土金属元素含量整体偏低而导致CIA异常偏高,因此不能真实反映剖面的化学风化程度.

古土壤记录了丰富的古气候和古环境信息,然而古土壤受后期地质作用影响常不易被正确地识别。甘肃张掖彩丘是白垩纪早期发育的彩色地层,目前详细的地层序列尚未建立。张掖彩丘表现为红色、黄色、灰色、紫色等多种颜色交替变化,通常被认为是河湖相沉积或洪积相沉积,然而野外考察发现大量的古土壤特征。野外观察识别古土壤主要从根迹、土壤结构和土壤发生层等方面,主要表现为红色根迹或青灰色晕状根迹,半干旱环境下形成的钙质淀积层,土壤在干湿交替环境下形成的粘土滑擦面,土壤发生层之间的过渡边界。本文通过对张掖彩丘地层的系统考察,建立了较为详细的厚760m的地层序列,根据古土壤的发育特征,识别出14种不同类型的古土壤,整个彩丘地层共计156个古土壤剖面,是独特的古土壤序列。14种古土壤类型与现代土壤类型对照,并与国际土壤分类对比,类比的现代土壤类型主要出现在南亚的亚热带或热带气候条件,说明白垩纪早期比现在更为温暖。根据古土壤发育程度序列,结合古土壤特征和地层特点,将古气候变化分成4个阶段,依次是湿润(0～268 m)、半干旱(268～550m)、湿润(550～740m)、干旱(740～760m)阶段。张掖彩丘古土壤的系统识别和发育程度序列的建立为进一步古气候研究奠定基础。

传统村落是我国古代居住文化的重要遗产,具有深厚的历史文化底蕴.以国家级传统村落河南省新县丁李湾村为研究对象,结合文献史料和实地访问调查,从形态学视角研究其景观格局特点及影响机制.结果表明:丁李湾村自形成、发展至衰落历经700多年,这其中受自然和当地传统宗族观念等多种因素综合作用影响;丁李湾村完备的山-水-林-田-村景观格局反映出村民尊重自然、因地制宜的生存智慧,其中对风水观念的重视是其创建吉祥家业的重要因素;目前,村落人口空心化现象严重,传统民俗文化日渐衰落,其可持续发展问题亟待解决.