天津滨海新区全新世沉积特征和沉积过程

从地貌、沉积和年代等方面分析了天津滨海新区的形成演变过程。研究区中部和南部主要为不同时期的古黄河三角洲,每期古黄河三角洲发育时均形成前三角洲、三角洲前缘和潮间带等沉积层序,三角洲的不同部位分别形成河控三角洲和潮控三角洲,三角洲废弃后,形成三角洲平原—贝壳堤—滨海沙坝的地貌体系。研究区北部的沉积层序和地貌特征反映了少泥沙河流在海洋动力逐渐减弱条件下的河海相互作用过程。     

江苏连云港全新世海滩岩的发现及意义

作者在江苏省连云港海滨首次发现了全新世海滩岩，这个发现使我国全新世海滩岩的北界从浙江省长涂岛（３０．２°Ｎ）北移到江苏连云港海岸（３４．９°Ｎ）。文章对连云港中－－晚全新世古气候、海平面变化、水动力条件、古地理环境等作了初步探讨。     

The isotopic record of atmospheric lead fall-out on an Icelandic salt marsh since AD 50

We report a record of atmospheric Pb deposition at a coastal site in western Iceland that spans the last two millennia. The elemental concentrations of Pb, Al, Li and Ti are determined using ICP-MS from a sediment monolith collected from a salt marsh. Multicollector (MC) ICP-MS analysis is used to obtain isotopic ratios of stable Pb. The Pb/Ti and Pb/Li ratios are used to separate natural Pb background concentrations from Pb derived from remote anthropogenic sources. The pollution record in western Iceland is subdued in comparison with Pb records from the European mainland, but the isotopic character, profile and timing of Pb deposition show good agreement with the atmospheric Pb fall-out reported from sites in Scandinavia and northwestern Europe. At the bottom of the sequence we isolate a low-level (0.1-0.4 mg kg^− 1) Pb enrichment signal dated to AD 50-150. The isotopic signature and timing of this signal suggest Roman metal working industries as the source. In the subsequent millennium there was no significant or very low (i.e. elemental concentrations < 0.01 mg kg^− 1) anthropogenic Pb deposition at the site up to, and including, the early Medieval period. Above a pumice layer, dated to AD 1226-1227, a small increase in Pb deposition is found. This trend is maintained until a more substantive and progressive increase is signalled during the late 1700s and early 1800s. This is followed by a substantial enrichment signal in the sediments (> 3.0 mg kg^− 1) that is interpreted as derived from industrial coal burning and metal working during the 19th and 20th centuries in northern Europe. During the late 20th century, significant fall-out from European fuel additives reached Iceland.     

山东安丘地区软土震陷及地震产生的土层构造新启示

通过地震调查、土工试验和¹⁴C测年,从沂沭断裂地震带安丘地区的全新世中—晚期湖沼相软土中,识别出了软土震陷灾害现象和地震产生的软土沉陷向斜褶曲、小尺度同震断层、狭缩-膨胀构造和震裂缝等共生土层变形构造,其中,软土沉陷向斜是直接反应震陷灾害的纵向土层变形。小尺度同震断层是地震产生的小断层,发育在沉陷向斜之下,其垂向延长0.5~1.8 m。沉陷向斜随着同震断层的产生而初现;又紧随断层向深部延伸而向下发展。地震振动使饱和软土发生触变,土质点从沉陷向斜的转折端向两翼发生流动,在此过程中,附加地震应力不断作用,结果形成了窄而深的沉陷向斜。软土震陷最大深度为1.08 m,平均震陷深度为0.68 m。推断当时的地震烈度达到Ⅷ度、震级超过M6。测得淤泥质土的¹⁴C年龄为 3901±33a B.P.,该地震事件约发生公元前19世纪。同震断层是形成震陷的重要诱导因素,这为认识软土震陷的形成机理提供了新资料;也为防治或减轻软土震陷的危害提出了新启示。因此,应重视软土下伏土层可能产生同震断层的隐患。     

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11500～10000aBP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10000～4500aBP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4500～3000aBP期间,气候以比较温和湿润为主,但在4200～4000aBP出现一个气候干旱事件,风沙活动强烈;近3000a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。     

单片再生剂量法测定全新世黄土等效剂量预热条件的研究

本文通过对双程序单片再生剂量法(Double-SAR)即同时测红外释光(IRSL)和红外之后的蓝光释光(Post-IR OSL)中普遍采用的几种预热温度和cut-heat温度进行了不同组合,然后测定了全新世黄土样品的等效剂量.测定结果表明:等效剂量对预热温度有一定程度的依赖性,而对cut-heat温度的依赖性显得更加明显,一般随cut-heat温度的升高而增大;同时在200-300 ℃的预热温度范围内,200-240 ℃的cut-heat温度下测定的等效剂量出现了一个显著坪区,且红外释光和红外之后的蓝光释光测得的结果最为接近.红外释光和红外之后的蓝光释光在以上预热温度和cut-heat温度条件下光释光信号的感量变化方向一致、变幅较小可能是测得的等效剂量较为一致的主要原因.这说明在200-300 ℃的预热温度范围内,200-240 ℃的cut-heat温度对于测定年轻的全新世黄土样品是较为可靠的.     

δ~(18)O and δD records of inactive ice wedge in Yitulihe, Northeastern China and their paleoclimatic implications

Discovered in the late 1980s, inactive ice wedges in Yitulihe in the north part of Da Hinggan Mountains, Northeastern China are the southernmost in the Northern Hemisphere, and they are important paleo-environmental indicators. Recently, research was carried out to analyze the hydrogen and oxygen isotopes of an inactive ice wedge from them. The plot of stable isotopes reveals three periods of temperature fluctuations centered approximately at 2.8, 2.3 and 1.9 ka BP. And the resultant temperature was probabl...     

The post-glacial history of northern Lake of the Woods: A multi-proxy perspective on climate variability and lake ontogeny

Lake of the Woods (LOW) is a large, morphologically and hydrologically complex lake of international importance, located in the provinces of Ontario and Manitoba and the state of Minnesota. A high-resolution sedimentary sequence retrieved near Kenora, Ontario, and spanning at least the past ~11,000?cal?yr?BP (calibrated years before present), was analysed for multiple environmental proxies with an emphasis on diatom assemblage composition and spectrally-inferred chlorophyll a. These biological proxies indicate that northern LOW was relatively nutrient-rich soon after its isolation from glacial Lake Agassiz ~10,000?cal?yr?BP. The post-glacial hydrological and environmental history of LOW was found to be controlled by both climate and isostatic rebound. During the low water phase of the mid-Holocene dry and warm period, abrupt and synchronous shifts across all proxies suggest that the northern basin had a relatively deep and well-mixed water column that experienced increases in nutrients and whole-lake algal production. This differs from recent limnological changes associated with warming since the late-1970s, where primary production increased concurrently with large shifts in diatoms indicative of increased thermal stability, but with little change in nutrients. The millennial-scale context of this study provides evidence that climate has long played an important role in algal dynamics in LOW, with implications for lake management strategies concerning recent increases in nuisance algal blooms on LOW.     

疏勒河冲积扇绿洲全新世古水文演化释光年代学

对甘肃疏勒河冲积扇前缘细土带3个具有代表性剖面的12个样品进行了光释光(OSL)年代测定,分别采用不同组分(粗颗粒、细颗粒)、不同技术(单测片再生(SAR)、简单多片再生(MARA)法)进行OSL测年,并相互对比检验,同时与有机碳14C测年结果相互对比,探讨冲积扇前缘复杂的沉积相中沉积物释光测年技术的可行性和可靠性.根据12个样品释光年龄测定值和8个样品有机碳14C测年结果,结合疏勒河绿洲全新世沉积层序、岩性、岩相以及不同沉积相与地下水溢出带的空间分布关系的观测资料,初步提出了疏勒河冲积扇地下水溢出带空间移动的时间框架.