晚全新世毛乌素沙地东南缘沉积物粒度特征及其指示的环境变化

地处我国东亚季风边缘区的毛乌素沙地,因其对气候变化响应敏感而成为研究古气候环境变迁的理想场所。利用毛乌素沙地东南缘厚273 cm的沉积地层,通过分析沉积物粒度端元特征和环境指示意义,并结合光释光(OSL)测年结果和磁化率指标,重建了研究区2.6 ka B.P.以来的环境变化过程。结果表明：(1)剖面沉积物的粒度组成以粗粉砂、极细砂和细砂为主,其中细砂最多,平均体积分数为57.29%;粉砂层细砂体积分数明显低于砂层,粗粉砂和极细砂显著增多;沉积物粒度频率分布曲线多呈现典型的风成沉积物特点,峰高且窄,分选性较好。(2)剖面沉积物粒度可分离为3个端元组分,端元EM1是最细的粒度端元组分,指示了短时间的强尘暴活动,端元EM2和EM3是在不同风动力条件下跃移搬运的亚组分,端元EM3指示了当地风沙活动的强弱。(3)研究区晚全新世环境变化过程可分为3个阶段。2.6 ka B.P.之前,冬季风较强,气候冷干;2.6 ka B.P.之后到近百年,冬季风减弱,气候趋于暖湿;近百年以来,风沙活动增强,人类活动影响较大。     

新疆喀纳斯湖沉积物粒度组分所揭示的环境特征

通过对新疆喀纳斯湖沉积物进行粒度分析,结合放射性同位素210Pb、137 Cs定年,研究了喀纳斯湖沉积物粒度敏感组分特征及其环境意义。喀纳斯湖沉积物以细颗粒组分(粒径小于16μm)为主,但1814~1830年(32~35cm深度处)和1893~1903年(18~20cm深度处)这两个时期的沉积物粒度特征发生了突变,粗颗粒组分(粒径大于16μm)尤其是粒径大于63μm组分含量迅速升高。对沉积物粒度频率曲线的分析表明,这两个时期的沉积物来源或沉积动力过程发生了显著变化。基于此,首先运用粒径-标准偏差法提取了沉积物中的敏感粒度组分C2(粒径为15~238μm),进而通过敏感粒度组分与器测气象数据的相关性分析和沉积物粗粒径(C)-中值粒径(M)图分析,研究了喀纳斯湖沉积物沉积时的动力条件。组分C2的含量大小与区域春季、夏季温度有关,反映了山地春季和夏季雪、冰融水入湖的强度,组分C2含量在1814~1830年和1893~1903年这两个时期的快速增大与水动力异常偏大有关,据此识别了两次显著的洪水事件。与区域树轮、冰芯记录及文献记载的对比分析表明,洪水事件的发生与对应时期内暖湿的气候特征有关。     

河北丰宁黄土粒度特征及其环境意义

对河北丰宁黄土剖面进行了系统的粒度分析，粒度参数显示:①丰宁剖面粒度以粗粉砂颗粒（粒径３２～６３μｍ）和砂级颗粒（粒径＞６３μｍ）为主，较西北黄土高原典型黄土的粒度偏粗，反映丰宁黄土中粗颗粒组分含量不仅受冬季风风力变化的控制，还受到其北部的浑善达克沙地活动的影响；②丰宁剖面在２３６ｃｍ 深度（年代为６１．５ｋａ）处砂颗粒成分（粒径＞６３μｍ）增加、平均粒径增大，分析认为是在全球气候变得更为寒冷干旱的背景下，由其物源区浑善达克沙地的扩张造成的。      

苏北盆地湖沼沉积记录的30~17 cal ka BP期间的气候变化

以苏北盆地里下河地区获取的SG钻孔沉积岩心为研究对象,进行了AMS14C年代、粒度、Rb 和Sr含量分析。结果表明,苏北盆地湖沼沉积的粒度分布和Rb/Sr 比值能够很好地指示东亚季风区的气候变化。根据粒度和Rb/Sr 比值的变化,可将苏北盆地30~17 cal ka BP期间的气候变化划分为3个阶段。在30.3~25.9 cal ka BP期间,降雨量相对增多,气候相对湿润;25.9~18.3 cal ka BP期间,降雨量减少,气候相对干旱;18.3~17.1 cal ka BP期间,降雨量又明显增加,气候相对湿润,期间还可能存在变干突变。SG钻孔沉积岩心的环境代用指标与西峰黄土平均粒径、葫芦洞石笋氧同位素有着很好的可比性,并且SG钻孔沉积岩心的黏土含量趋势线与北半球30°N六月的太阳辐射强度曲线极为相似,这表明苏北盆地的气候受太阳辐射驱动下的东亚季风系统影响明显。      

福建永安地区网纹红土粒度特征及其成因指示意义

为了探讨首次在闽西发现的网纹红土的成因,采用将永安地区网纹红土的粒度实验结果与典型风成沉积物、现代河流沉积物以及其他地区的网纹红土相对比的方法,对位于闽西永安地区的网纹红土剖面进行了粒度分析。结果表明:永安地区网纹红土以粉砂级组分为主,黏粒组分次之,砂级组分最少,全部样品属于黏土质粉砂;剖面从上到下粉砂级组分、黏粒组分逐渐增多,砂级组分明显逐渐减少;10~50 μm粒组体积分数均值为29.71%,远低于典型风成沉积物;沉积物岩性三角图、粒度参数特征、粒度参数散点图、M_z-A图和M_z-L图以及频率曲线显示永安地区网纹红土不是风积成因,但也不是典型的冲积成因;判别函数结果均为正值,显示了水成成因;永安地区网纹红土的成因是两方面的,为冲积成因下经过强烈化学风化作用的产物,福建其他地区、江西泰和以及广东东江一级阶地的网纹红土也具有相同成因。研究结果进一步明确了福建省境内网纹红土的分布,同时更深入理解与认识了网纹红土的成因。      

海平面上升—夹河断流背景下烟台套子湾海滩砂粒度变化

将烟台套子湾2021年与2005—2006年夹河口东西两侧海滩砂的粒度特征进行对比分析,揭示了近16年来套子湾海滩沉积物粒度特征变化对全球海平面上升—夹河入海水沙减少等过程的具体响应。研究表明,现代套子湾海滩砂样品以中砂、细砂为主,分选极好或好,标准偏差介于0.23~0.4,夹河口东侧的海滩砂平均粒径（Mz：1.39~1.64Φ）比西侧海滩砂平均粒径（Mz：1.47~1.91Φ）粗,主要组分中的粗砂和中砂含量比西侧高,表明现代夹河口东侧区域水动力较夹河口西侧强,该区海滩砂受到海洋动力的长期改造分选较好。近16年夹河口两侧海滩砂粒度明显粗化,表现在海滩砂平均粒径变粗、主要组分粒度变粗约0.5Φ、概率累积曲线的粗细截点变粗0.5~1Φ及滚动、跃移、悬移组分含量明显变化。夹河入海物质减少,海平面快速上升,导致海洋动力增强是研究区海滩砂粒度粗化、海滩侵蚀的主要原因,该研究结果可以为套子湾海滩防护提供科学指导。     

琼东海域沉积物元素组成变化揭示的全新世华南地区风化强度演变

【目的】探讨全新世以来华南地区陆地化学风化强度的变化及其控制因素。【方法】利用琼东海域沉积柱GH7的XRF扫描元素数据,从主量和微量元素中提取代表陆源输入的主成分PC1,分析华南沿海地区化学风化强度。【结果与结论】风化强度在13.2 ka BP以来经历了“强（13.2—7.5 ka BP）—弱（7.5—3.0 ka BP）—强（3.0—0 ka BP）”的变化,并在全球冷事件新仙女木、9.2 ka和8.2 ka时期均有明显减弱。PC1变化显示华南沿海地区风化强度大约在3 ka BP处于最强期,反映此时降雨量处于最大期,可能与热带辐合带（ITCZ）在此时期南移至低纬度有关。PC1频谱分析揭示风化强度存在一个约2 ka的周期,与厄尔尼诺（ENSO）周期一致,说明华南地区风化强度演变在千年尺度上很可能受ITCZ南移和ENSO的共同调控。     

陕西榆林风沙滩区全新世气候和环境变迁

榆林长城沿线处于环境变化敏感带,其风沙滩区沉积剖面的磁化率和粒度分析结果显示,该区全新世早期11 500~10 000 a BP随着全球气候的逐渐转暖,磁化率、黏粒和粉沙含量逐渐增高;全新世中期的10 000~4 500 a BP气候相对比较湿润,植被覆盖度增大,风沙活动减弱,地表沉积物当中粉沙和黏土成分含量显著增大,风化成壤作用增强,地表发育沙质弱古土壤;全新世中期后段的4 500~3 000 a BP期间,气候以比较温和湿润为主,但在4 200~4 000 a BP出现一个气候干旱事件,风沙活动强烈;近3 000 a以来,气候显著干旱化,波动频繁,地表风沙沉积物显著变粗,表现出有5次沙漠扩张。该区生态环境演化、人文历史变迁基本上是自然因素与人为活动综合作用的结果,以自然演化为主,近代人为因素对环境变化起着加强和放大作用。     

泥岩与页岩特征辨析

细粒沉积岩类型复杂,原因是其定义基于结构粒度概念,缺乏对矿物成分的有效约束,加之,不同学者是在不同尺度下对构造现象进行描述,使得细粒沉积岩缺乏较为科学、系统的分类。为辨析泥岩与页岩的特征,通过大量调研国内外沉积学教材及相关文献发现:细粒沉积物(粒径小于62.5 μm)的概念自20世纪30年代进入人们的视野,后被广大研究人员广泛接受,且大多数学者普遍认为可依据粒度大小,进一步将细粒沉积物划分为黏土级颗粒(粒径小于3.9 μm)和粉砂级颗粒(粒径介于3.9~62.5 μm之间)。但是,国、内外沉积学界对细粒沉积物“泥”(泥级颗粒)的粒径划分不同,欧美学者一般将“泥”界定为粒径小于62.5 μm,包括黏土级颗粒与粉砂级颗粒。在我国,自20世纪50年代开始,沿用了前苏联的方案,“泥”的粒径对应黏土级颗粒即小于3.9 μm,这一分歧是导致泥岩与页岩等概念使用混乱的根本原因。概而言之,固结的泥岩具有与页岩相同的粒级结构和组分,但是不具备页岩的“纹层”或“页理”构造特征;辩证而言,“纹层”强调沉积过程所形成的垂向层理差异,而“页理”则是成岩过程受风化作用影响形成的力学薄弱面。从泥岩和页岩的矿物组成看,存在石英和长石硅质矿物、黏土矿物,碳酸盐矿物的混合沉积作用的影响,需要从沉积成因出发,结合构造特征,综合矿物类型、有机质丰度和颗粒来源等因素对泥岩和页岩进行岩性岩相分类。实践表明,页岩油气的开发动用需要地质工程一体化协同,辨析泥岩和页岩的特征差异性对产层优选具有重要意义。      

江苏滨海平原弱透水层封存的古咸水及其运移过程

滨海平原弱透水层广布且多赋存古咸水，其盐度分布及运移过程深刻影响着含水层地下水的演变，却得到甚少关注。采集了江苏滨海区7个浅层钻孔弱透水层原状样品，压榨法收集孔隙水。利用孔隙水天然示踪剂ρ（Cl-），ρ（Br-）剖面和数值模拟分析了弱透水层孔隙水盐度特征和运移机制。得出浅层孔隙水ρ（Cl-）垂向剖面存在2个趋势:①峰值在表层，沿深度逐渐下降；②峰值在深度25m左右，向两端浓度降低。孔隙水ρ（Cl-）为486.2~38 036.7 mg/L，Cl/Br比值为72~360（均值241）。ρ（Cl-）与Cl/Br比值关系及剖面分布说明孔隙咸水为海相成因，来自于全新世海侵时期的古海水，并受到后期淡水的稀释。弱透水层孔隙水一维垂向运移数值模型表明海侵-海退事件控制了海岸带弱透水层孔隙水的盐度演变，全新世古海水仍封存在沉积物中，更新世时期的海水已被驱替。孔隙水运移以扩散为主，垂向运移速率为0.43~15.8 mm/Ma。在相对高渗透性的粉砂地层中，可能还受到侧向对流的影响。弱透水层中古海咸水的重新分布，尤其在地下水超采条件下，可能成为地下水的重要咸化来源。      

甘肃通渭县黄土堆积区全新世环境变迁

通过对甘肃通渭县四家庙全新世黄土剖面的粒度和磁化率分析。并依据前人研究成果对年均气温和年均降水量的相应恢复，揭示了该区全新世期间气候演化的特点和规律。分析认为，研究区全新世以来的环境变化是不稳定的，无论古土壤发育期还是黄土堆积期，气候都具有频繁的次级波动。尤其在全新世中期。两层古土壤间的黄土夹层，反映该区在全新世大暖期经历过一次历时千年之久的气候显著恶化事件。     

Environmental evolution of Gongwang Mountains during Holocene in northeastern Yunnan, China

This paper presents the study on two continuous glacio-lacustrine sedimentary deposits, Laotanfang (3 597 m) and Shibantang (3 689 m) located on the southern and northern sides of Hulifang peak in Yunan, China. Environmental change indexes are constructed for each deposit, based on grain size, geochemical and pollen analysis, environmental magnetic susceptibility, and 14C dating. The study of climatic environmental change since the Holocene epoch in this region shows that the climate fluctuated at different stages during the early Holocene, that is, the climate was cool and wet during 8 4-7 7 ka, cold and wet during 7 7-6 5 ka, cold and dry during 6 5-4 7 ka, cool and wet during 4 7-2 1 ka, warm and wet during 2 1-1 0 ka, and warmer and wet since 1 ka. These findings reflect the overlapping influences of the southwest and southeast monsoons in different times during the Holocene in the north part of southwestern China are in accord with other Holocene climate change models in this part of China.     

Millennial-centennial scales climate changes of Holocene indicated by magnetic susceptibility of high-resolution section in Salawusu River valley,China

The upmost segment(Holocene series)of the Milanggouwan stratigraphic section(MGS1)in the Salawusu River valley shows 11 sedimentary cycles of dune sands and fluvio-lacustrine facies,or dune sands and paleosols.The analysis of the magnetic susceptibility of this segment suggests that there are 11 magnetic susceptibility cycles with the value alternating from low to high,in which the layers of the dune sands correspond to the lower value of the magnetic susceptibility and the layers of fluvio-lacustrine facies and paleosols correspond to the higher peaks.The study reveals that the low and high magnetic susceptibility values indicate the climate dominated by cold-arid winter monsoon and warm-humid summer monsoon of East Asia,respectively,and the study area has experienced at least 22 times of mil-lennial-centennial scales climate alternation from the cold-arid to the warm-humid during the Holocene.In terms of the time and the climate nature,the variations basically correspond to those of the North Atlantic and some records of cold-warm changes in China as well.They might be caused by the alternation of winter and summer monsoons in the Mu Us Desert induced by global climate fluctuations in the Holocene.     

华北盆地北缘宝坻断裂晚更新世以来的活动性研究

通过人工浅层地震反射剖面发现,在香河县荆庄地区,宝坻断裂表现为一条近EW走向的南倾正断层,剖面上呈铲状,对第四系沉积具有一定的控制作用,为一条第四纪活动断裂。通过部署在断层两侧的构造观察孔岩芯对比及¹⁴C测年、光释光测年数据可知,宝坻断裂上断点距地表5~7 m左右,主要活动时间为晚更新世,全新世及中更新世晚期无明显活动。岩芯对比表明,距今10万年以来,宝坻断裂共发生2次地震活动,累积位移2.6 m,其中最近一次地震发生于22 740±70 a BP,同震位移1.4 m;另一次地震发生于距今97.1±4.4~98.0±5.3 ka之间,同震位移1.2 m。根据本次钻孔结果,结合前人对张家口-渤海构造带东段断裂活动性及发震规律的研究,判断宝坻断裂全新世以来整体处于不活跃状态,诱发中强地震和大地震的可能性较低。此外,香河县荆庄一带发育的地裂缝为受宝坻断裂控制的构造型地裂缝,断裂南北两侧的不均匀地面沉降产生的剪切应力会加速荆庄地裂缝的发展。     

CSCO_3 CYCLES IN SALAWUSU RIVER BASINSINCE 150KA B.P.

About 70years ago，Frenc卜卜alaeohdoglst回LL sc卜dars al卜ome and a卜road卜ave successively con－HARD de Chardin P．et al．Initiated the Quaternary ducted large amount ofwork on the Later Quaternarygeologlcal research In the ＞alawusu River Basin of strata（TEILHARD，1924； YUAN，1978； LI，1987；desert region of Northern China and established th，ZHENG，1989； SUN et al，1996； LI et al，1993），Salawusu Formation门EILHARD，1924）．Sine，then，palaeobiology…     

Change in Sediment Provenance Near the Current Estuary of Yellow River Since the Holocene Transgression

Sedimentary sequence and sediment provenance are important factors when it comes to the studies on marine sedimentation. This paper studies grain size distribution, lithological characteristics, major and rare earth elemental compositions, micropaleontological features and ~(14)C ages in order to examine sedimentary sequence and sediment provenance of the core BH6 drilled at the mouth of the Yellow River in Bohai Sea. According to the grain size and the micropaleontological compositions, 4 sedimentary units have been identified. Unit 1(0–8.08 mbsf) is of the delta sedimentary facies, Unit 2(8.08–12.08 mbsf) is of the neritic shelf facies, Unit 3(12.08–23.85 mbsf) is of near-estuary beach-tidal facies, and Unit 4(23.85 mbsf–) is of the continental lake facies. The deposits from Unit 1 to Unit 3 have been found to be marine strata formed after the Holocene transgression at about 10 ka BP, while Unit 4 is continental lacustrine deposit formed before 10 ka BP. The provenances of core BH6 sediments show properties of the continental crust and vary in different sedimentary periods. For Unit 4 sediments, the source regions are dispersed while the main provenance is not clear, although the parent rock characteristics of a few samples are similar to the Luanhe River sediments. For Unit 3, sediments at 21.1–23.85 mbsf have been mainly transported from the Liaohe River, while sediments above 21.1 mbsf are mainly from the Yellow River and partially from the Liaohe River. For Unit 2, the sediments have been mainly transported from the Yellow River, with a small amount from other rivers. For Unit 1, the provenance is mainly the Yellow River catchment. These results help in better understanding the evolution of the Yellow River Delta.     

Sedimentary evolution of the Holocene subaqueous clinoform off the southern Shandong Peninsula in the Western South Yellow Sea

Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14 C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15–40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene(about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units(DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface(MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a highstand systems tract from middle Holocene(about 7–6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is controlled mainly by coactions of multiple factors such as the Holocene sea-level changes, sediment supplies and coastal dynamic conditions, the development of the clinoform is genetically related with the synchronous clinoform or subaqueous deltas around the northeastern Shandong Peninsula and in the northern South Yellow Sea in the spatial distribution and sediment provenance, as previously reported, with all of them being formed from the initial stage of the Holocene up to the present.     

The Holocene warm-humid phases in the North China Plain as recorded by multi-proxy records

The grain size and palinology of sediment and the frequency of 14C dada provide an integrated reconstruction of the Holocene warm-humid phases of the North China Plain. Two clear intense and long-lasting warm-humid phases were identified by comprehensive research in this region. The first phase was dated back to the early Holocene (9 000–7 000 a BP), and the second was centered at 5 000–3 000 a BP. The warm-humid episode between 9 000 and 7 000 a BP was also recognized at other sites showing global climatic...     

Environmental anomalies in the northeastern East China Sea during the last 3 000 years: implications for El Niño activity in the Holocene

To reconstruct the productivity changes for the last 10 500 a in the northeastern East China Sea (ECS), biogenic compounds (such as carbonate, organic carbon and opal), marine micropaleontological fossils (planktonic foraminifera, benthic foraminifera, radiolarian and silicoflagellate) and the compositional characters of benthic foraminifera fauna analyses were carried out on a sediment core DOC082 obtained from the western slope of Okinawa Trough (29°13.93′N, 128°08.53′E; 1 128 m water depth). The long-term changes of biogenic and micropaleontological proxies display some similarities through the last 10 500 a, which show three different phases: lower values are recorded during the early and middle Holocene (before about 4 000 a BP), followed by an abrupt and remarkable increase at about 4 000 a BP, the late Holocene (after about 3 000 a BP) is characterized by continuously high values. The multi-proxy data of paleoproductivity and percents of benthic foraminifera genera (Uvigerina and Bulimina) show that during the early and middle Holocene (10 500–4 000 a BP) productivity was relatively low with a sudden and distinct increase at about 4 000 a BP, and the late Holocene (3 400–0 a BP) is marked by significantly higher productivity. Also, the radiolarian-based sea surface temperature (SST) records reveal a distinct decline in SST in the late Holocene after 3 200 a BP, very different from the early and middle Holocene. For the last 3 000 a, the enhanced biological productivity and distinctly lower SST indicate a major change of oceanographic conditions in the northeastern ECS. These marine environmental anomalies are consistent with other paleoclimatic records for the late Holocene in the Chinese continent and its surrounding regions. After analyzing the mechanisms of modern productivity and SST changes in the northeastern ECS, and based on the climatic anomalies in the Chinese continent and variations in the Kuroshio Current during modern El Niño periods, we suggest that the anomalous environmental conditions in the northeastern ECS may imply intensified El Niño activity during the late Holocene.     

Response of river terraces to holocene climatic changes in Hexi Corridor, Gansu, China

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