北极王湾冰海沉积物类型及沉积作用

王湾作为发育于现代冰盖边缘的开放性峡湾,具有典型的冰海沉积特征,使其成为研究冰海沉积作用的良好场所。对湾内54个表层沉积物进行了粒度分析,并计算了其粒度参数。表层沉积物与其他地区冰碛物、冰水沉积物及冰海沉积物的对比,验证了应用粒度参数散点图在区分冰川亚环境过程中的有效性。参照冰海沉积物划分方案,将王湾的冰海沉积物划分为3类:基本缺乏粉砂和泥的Ⅰ型残副冰碛物、含砂砾的Ⅲ型沉积物和基本缺乏砂砾的Ⅳ型混合副冰碛物。对王湾沉积物的来源和沉积作用作了初步的探讨。

南极普里兹湾全新世的冰海沉积

ＮＰ９３－２柱样采自南极普里兹湾陆架区域，具有明显的冰海沉积作用特征，受冰川和海洋共同作用。粒度参数、矿物组成、微体古生物和地球化学等资料揭示了该区１２９３７ａ以来的沉积作用特征和沉积环境与气候变动的信息。大约在１０ｋａ，气候波动突然明显回暖，冰筏源碎屑物质增加，晚期还有一个短暂气候波动。

冰海沉积物识别标志的初步探讨

冰海沉积物的识别一直是个比较复杂的问题。本文通过比较冰海沉积物、冰川沉积物和块状流沉积物的粒度、颗粒形状、侧向分布、厚度及组构等方面的特征,找出其异同点,并据实际资料,提出冰海沉积物识别标志的初步探讨。

东南极海域冰海沉积物的类型与特征

本文对采自东南极海域的表层沉积物的粒度类型、成因类型、特征和沉积作用进行了初步研究,指出它们主要由冰筏陆源碎屑和海洋生源组份组成,为冰川沉积经海洋环境改造的产物。

南极布兰斯菲尔德海峡冰海沉积环境与沉积模式初探

南极布兰斯菲尔德海峡晚更新世以来沉积物具有明显的冰川-海洋环境标志,为典型的冰海沉积物。本文通过43个站位表层和柱状沉积物的粒度、成分、结构构造、微体古生物、石英颗粒表面结构等特征综合分析,对研究区的冰海沉积物类型及其分区和沉积环境进行初步研究,并讨论间冰期/高水位和冰期/低水位的沉积模式。冰海沉积物可分为残副冰碛物和混合副冰碛物两类;不同类型的冰海沉积物有着不同的介质条件和相应的生物组合,反映一定的沉积环境,研究区现代冰海沉积物类型可分为7个特征明显不同的区域;间冰期/高水位和冰期/低水位的沉积模式具有明显不同的特征,受控于全球气候演变和岸线轮廓、海底地形及水文条件等环境因素的制约。

中国晚前寒武纪的冰川活动

晚前寒武纪末期是中国地质历史上冰川活动最重要时期,也是全球范围内冰川广泛发育的时期。冰川活动是地球发展进程中的一次重要地质事件,因此有些学者曾建议将这时期称作寒冷纪或冰川纪。最近,我国不少学者根据生物演化和古地理古构造特征认为700Ma是一个重要界线,建议将震旦系底界定在700Ma,其下冰川活动广泛发育的800—700Ma阶段另建一纪,暂称扬子纪,作者赞同这一建议。

Development of Sedimentary Environment in the Northeastern South China Sea Since the Last Glacial Stage

Core D （21°23′02″N, 116°47′13″E, water depth 405 m） was sampled from the upper slope from the northeastern South China Sea （SCS） and applied to analyze the sedimentary environmental change in this sea area since the last glacial stage. The results of grain size analysis, diatom analysis and detrital mineral analysis were well matched. We divided the core D into two layers. The surface sand layer （0 - 2 cm） consisted of residual sediments, which might be originally the sediment in the late Pleistocene and later suffered from being transformed in the post glacial transgression. The lower layer （2 - 130 cm） was quite different from the surface one, which might mainly result from a neritic sedimentary environment in the last glacial stage. Two sedimentary cycles could be detected in the core D： regression during Marine isotope stage （MIS） 4 to transgression during MIS 3 and regression during MIS 2 to transgression during the post glacial.

动物演化的分界线——奥陶纪

奥陶部落 奥陶部落中的“奥陶”是1879年由来自英国的地质学家提出的,代表了在英国北威尔士露出的岩层。岩层发现地曾经居住着古老、神秘的奥陶部族,故名奥陶纪。奥陶人是曾经居住在英国的凯尔特人,在被罗马人入侵前,他们养着羊群,耕种着土地,享受着大自然所给予的恩赐。尽管他们建造了坚固的据点和山区堡垒,并且不畏死亡地保卫着家园,但最终免不了被罗马人占领国家的悲惨命运。

Optically stimulated luminescence dating of young glacial sediments from the eastern Qinghai-Tibetan Plateau

Poor bleaching is a significant problem for Optically Stimulated Luminescence(OSL) dating of glacial sediments. Five young glacial samples(including two modern analogues) from different depositional settings were collected beyond the Yingpu Glacier in the eastern Qinghai-Tibetan Plateau. De was determined using different OSL methods. The luminescence characteristics and dating results showed that the large aliquot quartz Blue Stimulated Luminescence(BSL) is more applicable than polymineral infrared stimulated luminescence(IRSL) method. Small aliquot quartz BSL results showed poor luminescence properties due to low luminescence sensitivity of quartz in this area. The dating results also indicated that glaciofluvial samples deposited close to ice margin(~40 m and ~700 m) and supraglacial debris dominated lateral moraine samples are relatively well-bleached, whereas samples from ground moraine and low terminal moraine were poorly bleached, probably due to containing subglacial and englacial debris. The residual doses of glaciofluvial and lateral moraine crest samples were below a few Gy and age overestimations were below a few hundred years. The ground moraine and low terminal moraine samples had residual doses as high as ~110 Gy, and ages were overestimated by ~15-17 ka.

Sedimentary evolution since the late Last Deglaciation in the western North Yellow Sea

To decipher the sedimentary evolution and environmental changes since the late Last Deglaciation, two gravity cores were analyzed from the western North Yellow Sea (NYS). The two cores (B-L44 and B-U35) were sampled for grain size, clay minerals, detrital minerals, and 14C dating. They are comparable in lithofaies, and the observed succession was divided into four depositional units based on lithology and mineral assemblages, which recorded the postglacial transgression. Depositional unit 4 (DU 4) (before 11.5 ka) was characterized with enrichment in sand, and was interpreted as nearshore deposits in shallow water during the Younger Dryas Event. DU 3 (11.5-9.6 ka) displayed a fining-upward succession composed of sediments from local rivers, such as the Huanghe (Yellow) River, and from coastal erosion, which clearly were related to the Early Holocene transgression. Stable muddy deposition (DU 2) in NYS began to form at about 9.6 ka, which received direct supply of fine materials from the Shandong subaqueous clinoform. It is believed that the Yellow Sea circulation system played a major role in controlling the formation of fine sediment deposition in DU 1 (after 6.4 ka) after the sea level maximum.

Heavy mineral stratigraphy of sediments from the southern outer shelf of the East China Sea since the last glaciation using fuzzy C-means cluster method

Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages, and the sediment sources and depositional dynamics of the environment reconstructed. The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea. Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf （cm below sea floor）, the core might have previously been divided into three sediment strata marked with units Ⅰ, Ⅱ and Ⅲ, which would be consistent with the divided sediment stratum of the core using minor element geochemistry. The downcore distribution of heavy minerals divided the sedimentary sequence into three major units, which were further subdivided into four subunits. The interval between 0 and 63 cmbsf of the core （unit Ⅰ）, which spans the Holocene and the uppermost late Pleistocene, is characterized by a hornblende-epidote-pyroxene assemblage, and contains relatively a smaller amount of schistic mineral and authigenic pyrite. In comparison, the interval between 63 and 228 cmbsf （unit Ⅱ）, is representative of the Last Glacial Maximum （LGM）, and features a hornblende-epidote-magnetite-ilmenite assemblage containing the highest concentrations of heavy minerals and opaque minerals. However, the interval between 228 and 309 cmbsf （unit Ⅲ）, which spans the subinterglacial period, is characterized by a hornblende-authigenic-pyrite-mica assemblage. Relative ratios of some heavy minerals can be used as tracers of clastic sediment sources. The lower part of the sediment core shows the highest magnetite/ilmenite ratio and relatively high hornblende/augite and hornblende/epidote ratios. The middle core shows the highest hornblende/augite and hornblende/epidote ratios, and the lowest magnetite/ilmenite ratio. The upper part exhibits a slightly higher magnetite/ilmenite ratio, and also the lowest hornblende/augite and hornblende/epidote ratios. The distribution of the mineral ratio is consistent with stratigraphic division in heavy mineral data using correspondence analysis and fuzzy C-means clustering. Variations in heavy mineral association and mineral ratio in core Q43 revealed changes in provenance and depositional environment of the southern outer shelf of the East China Sea since the late Pleistocene, well corresponding to interglacial and glacial cycles.

Paleo-fluvial sedimentation on the outer shelf of the East China Sea during the last glacial maximum

Evidence from lithology, foraminiferal assemblages, and high-resolution X-ray fluorescence scanning data of core SFK-1 indicates tidally influenced paleo-fluvial sedimentation during the last glacial maximum (LGM) on the outer shelf of the East China Sea. The paleo-fluvial deposits consist of river channel facies and estuarine incised-valley-filling facies. Different reflections on the seismic profile across core SFK-1 suggest that the river channels shifted and overlapped. River channel deposition formed early in the LGM when sea level fell and the estuary extended to the outer shelf. Channel sediments are yellowish- brown in color and rich in foraminifera and shell fragments owing to the strong tidal influence. Following the LGM, the paleo-river mouth retreated and regressive deposition of estuarine and incised-valley-filling facies with an erosion base occurred. The river channel facies and estuarine incised-valley-filling facies have clearly different sedimentary characteristics and provenances. The depositional environment of the paleo-river system on the wide shelf was reconstructed from the foraminiferal assemblages, CaCO3 content and Ca/Ti ratio. The main results of this study provide further substantial constraints on the recognition of late Quaternary stratigraphy and land-sea interactions on the ECS shelf.

Palaeoclimatic evolution recorded by multidicipline in sediments in gahai lake, qaidam basin since late last deglacial

Based on the analyses of Loss-on-Ignition （LOI）, carbonate content and sediment characteristics, this paper reconstructs the climatic and environmental evolution of the Gahai lake area since the late Last Deglacial Period. The results cover the late Last Deglacial Period and the Holocene. The climate was very unstable and rather arid during the late Last Deglacial Period. The Holocene can be divided into three periods： the early Holocene （11360-8240 cal aB. P. ）, which was dry but unstable and featured rising temperatures, the mid-Holocene （8240-3200 cal aB. P. ）, which was warm and wet and the late Holocene （ since 3200 cal aBP）, which was cold and dry. Results also show a warm-wet event around 1500 cal aB. P.