华南海岸沙丘岩形成与全新世气候变化(英文)

Coastal dune rocks in China are eolian sands cemented by calcium carbonate under subaerial conditions,widely distributing on the tropical and subtropical coasts of South China.Particular temperature and precipitation as well as local wave and landform conditions are required for the formation of the dune rocks.A correspondence was found between Holocene environmental changes and coastal dune rock development by comparing the features of the sea-level and climate changes in the Holocene period with the ages,...     

华南海岸沙丘岩形成与全新世环境变化的关系

海岸沙丘岩是热带亚热带地区由碳酸盐胶结的海岸风成堆积,其成岩过程的各个阶段需要特定的水热和地貌条件。对华南海岸沙丘岩的形成年代、堆积高度、出露地点进行统计分析,将其特征与全新世环境变化事件作对比, 结果显示华南沿海沙丘岩的形成过程与全新世气候变化及海平面变化等事件有很好的对应关系, 能很好地解释我国沙丘岩研究中一些尚未解决的问题：华南沿海缺少5000a BP以前沙丘岩是因为当时的沙丘岩形成于低海面,后来因海面上升而被淹没;3000a BP前后海岸风沙大规模堆积是大暖期结束后气温下降的结果;华南沿海沙丘岩的胶结主要发生在中世纪暖期;华南沿海缺少年代小于1000aBP沙丘岩是因为近千年来气候条件下,不适合沙丘岩的胶结。     

中国海岸风沙沉积记录的环境变化

海岸是陆、海、气相互作用的地带。海岸风沙沉积是这一特殊动力环境的产物,是研究海岸环境演变及海平面变化的良好信息载体。中国海岸主要存在3种风沙沉积,分别为“老红砂”、沙丘岩及海岸沙丘。本文通过比较已报道的风沙堆积的物质组成、地层变化等,进一步总结了海岸风沙沉积的特征;选择已开展绝对测年的沉积剖面,利用概率密度函数分析了风沙沉积年代的分布特征,考察了中国海岸风沙活动历史,结合其他气候记录,探讨了不同地质历史时期海岸风沙堆积的关键影响因素。结果表明：“老红砂”沉积主要记录了冰期-间冰期尺度的风沙活动,在120 ka BP前后、73—55 ka BP等时期,风沙活动主要与海平面下降时陆架提供的丰富沙源和强盛的冬季风有关;而在105 ka BP、80 ka BP前后,风沙活动与高海平面时期丰富的沙源或季风气候的季节性增强有关;55 ka BP以来风沙活动强度降低更多地反映了沉积记录保存环境的变化,末次冰期海岸风沙沉积大多分布在现代海面之下,并不代表实际的海岸风沙活动减弱。相比之下,海岸沙丘沉积所记录的风沙活动主要发生在近3 000 a,可能与中国海岸冬季风的增强有关。     

Morphology and chronostratigraphy of a coastal dunefield; Groote Eylandt, northern Australia

A coastal dunefield on Groote Eylandt, in the Gulf of Carpentaria, northern Australia, is stratigraphically described and dated using the coarse fraction thermoluminescence dating technique. Four phases of dune activity have been identified: (1) Modern active transverse and parabolic dunes. (2) A parabolic dunefield apparently stabilized less than 2000 yr BP. (3) A parabolic dunefield stablized between 6000 and 4800 yr BP. (4) A basal dunefield unit emplaced prior to 100,000 yr BP.The current dune systems are an expression of dune activation and stabilization events in the Holocene, but were formed from the deflation of an extensive pre-Holocene dunefield. The destruction of the pre-Holocene dunefield appears to have been caused by sea-level rise at the end of the Pleistocene and during the early Holocene. The ages derived from the dunefield accord well with chronostratigraphic investigations of coastal dune systems elsewhere in northern Australia and support theories of regional environmental change during the Holocene.     

近40ka来海南岛海岸沙地气候与环境演变

选择海南岛东、西海岸具有代表性和高分辨率特征的木堆、棋子湾等地层剖面,在建立年代序列的基础上,对风成沙粒度组成与参数、SC/D值及磁化率等代用指标的研究表明,末次冰期间冰阶时气候相对温暖,滨海平原上河流三角洲前移,湿地、沙丘与交错分布;末次盛冰期时气候干凉,海岸沙地上形成了多道平行延伸的古沙垄(丘),并与大陆架古沙丘形成连续性沉积;末次冰消期时气候快速变化,古沙垄(丘)或加积发育或固定成壤;全新世以来气候回暖并波动变化,次生沙丘经历多次半固定、固定－沙丘加积、活化的演变。     

Late Pleistocene dune construction in the Central Sand Plain of Wisconsin, USA

Wisconsin's Central Sand Plain east of the Wisconsin River is composed of eolian sand forming high-relief dunes surrounded by sand sheets and scattered low-relief dunes. To establish a maximum age for dune formation, three samples for optical dating were taken from glacial Lake Wisconsin lacustrine sediment that underlies eolian sand. These age estimates range from 19.3 to 13.6ka. Age estimates taken from within or at the base of the dunes range from 14.0 to 10.6ka. Samples taken from < 2m of the ground surface were slightly younger, indicating dunes were stabilized between 11.8 and 5.5ka. The younger ages near the surface of some dunes were most likely the result of pedoturbation or localized problems with applying the optical dating method. The majority of the optical age estimates from dunes (18 of 21) indicated that most of the dunes were active between 14 and 10ka and that most dune activity ended by 10ka. These ages suggest that localized activity on dune crests may have occurred in the Holocene but would have been limited to < 1m of sand accumulation. The timing of dune activity and the lack of any significant Holocene reactivation suggest that dune activation in this setting cannot be attributed solely to changes in aridity. Instead, we attribute dune formation to changes in sediment availability from either sand inputs from the Wisconsin River or the melting of permafrost.     

毛乌素沙漠东南缘滴哨沟湾剖面DGS1层段粒度特征及其指示的全新世气候变化

分析滴哨沟湾剖面全新统DGS1段的粒度数据,认为流动沙丘砂、泥炭、砂质古土壤、古固定-半固定沙丘砂到湖沼相和次生黄土的颗粒总体上变细,分选变差。结合腹足类动物化石和湖沼相地层中石英砂粒表面电镜扫描,认为DGS1粒度结果实际上是全新世以来多次冬夏季风的交互演替过程的气候-地质记录。据此,将DGS1粒度信号记录的全新世气候分为4个阶段——全新世早期好转期、全新世鼎盛期、大暖期向寒冷期转变波动期和降温不稳定的沙漠化频繁变化时期。     

福建海岸的风成沉积

福建沿岸多处发育现代海岸风成沉积, 采用现代风砂所总结的特征作为识别标志, 研究了3000-4000年前产生的某些生物碎屑岩和3-4万年前开始形成并广泛分布的老红砂, 证明它们皆为风成, 因此晚更新世以来这里就具有风成沉积发育的条件。海岸风成沉积大规模发育出现在高海面之时, 分布也不遵循地带性规律, 这些均与沙漠地区的风砂不同。     

海南岛东北部海岸沙丘的沉积构造特征及其发育模式

海岸沙丘沉积构造中既有大型交错层理,也具某些区别于内陆沙丘构造的特征,如厚层顶积层的保存及变形层理的普遍存在。 本区海岸沙丘形成于东北季风,沙源来自海滩砂。从海滩后滨向陆地的沙丘类型依次是海岸前丘、横向沙丘和新月形沙丘、抛物线沙丘、纵向沙丘、海岸沙席。其中海岸前丘和沙席为海岸沙丘区别于内陆沙丘的特有类型。本区海岸沙丘的发育开始于3000年前。     

A Holocene history of dune-mediated landscape change along the southeastern shore of Lake Superior

Causal links that connect Holocene high stands of Lake Superior with dune building, stream damming and diversion and reservoir impoundment and infilling are inferred from a multidisciplinary investigation of a small watershed along the SE shore of Lake Superior. Radiocarbon ages of wood fragments from in-place stumps and soil O horizons, recovered from the bottom of 300-ha Grand Sable Lake, suggest that the near-shore inland lake was formed during multiple episodes of late Holocene dune damming of ancestral Sable Creek. Forest drownings at 3000, 1530, and 300 cal. years BP are highly correlated with local soil burial events that occurred during high stands of Lake Superior. During these and earlier events, Sable Creek was diverted onto eastward-graded late Pleistocene meltwater terraces. Ground penetrating radar (GPR) reveals the early Holocene valley of Sable Creek (now filled) and its constituent sedimentary structures. Near-planar paleosols, identified with GPR, suggest two repeating modes of landscape evolution mediated by levels of Lake Superior. High lake stands drove stream damming, reservoir impoundment, and eolian infilling of impoundments. Falling Lake Superior levels brought decreased sand supply to dune dams and lowered stream base level. These latter factors promoted stream piracy, breaching of dune dams, and aerial exposure and forestation of infilled lakebeds. The bathymetry of Grand Sable Lake suggests that its shoreline configuration and depth varied in response to events of dune damming and subsequent dam breaching. The interrelated late Holocene events apparent in this study area suggest that variations in lake level have imposed complex hydrologic and geomorphic signatures on upper Great Lakes coasts.     

Multi-proxy evidence of postglacial climate and environmental change at Two Frog Lake,central mainland coast of British Columbia,Canada

Pollen and diatoms preserved in the radiocarbon dated sediments of Two Frog Lake in the Seymour-Belize Inlet Complex of the central mainland coast of British Columbia document postglacial climate change. Two Frog Lake was isolated from the sea prior to 11,040 ± 50 yr BP (13,030 cal. yr BP) when the climate was cool and dry, and open Pinus contorta woodlands covered the landscape. These woodlands were replaced by a mixed conifer forest ca. 10,200 yr BP (ca. 12,300 cal. yr BP) when the climate became moister. A relatively dry and warm early Holocene climate allowed Pseudotsuga menziesii to migrate northward to this site where it grew with Picea, Tsuga heterophylla and Alnus. The climate became cooler and moister at ca. 8,000 yr BP (ca. 9,200 cal. yr BP), approximately 500–1,000 years prior to sites located south of Two Frog Lake and on the Queen Charlotte Islands, but contemporary with sites on the northern mainland coast of British Columbia and south coastal Alaska. Climate heterogeneity in central coastal British Columbia appears to have occurred on a synoptic scale, suggesting that atmospheric dynamics linked to a variable Aleutian Low pressure system may have had an important influence on early Holocene climate change in the Seymour-Belize Inlet Complex. The transition to cooler and moister conditions facilitated the expansion of Cupressaceae and the establishment of a modern-type coastal temperate rainforest dominated by Cupressaceae and T. heterophylla. This was associated with progressive lake acidification. Diatom changes independent of vegetation change during the late Holocene are correlative with the mid-Neoglacial period, when cooler temperatures altered diatom communities.     

珠江口岛屿全新世沙堤的年代与沉积环境

通过对珠江口岛屿小型海湾如珠海淇澳岛和澳门黑沙滩一级阶地上的古沙坝/沙丘进行光释光（OSL）年代测定、粒度分析,结果表明,全新世潮间带砂体沉积的底部年代根据光释光测年结果和沉积速率推算,超过9 ka。海岸带形成的古沙坝或风成砂质沉积的光释光测年结果大部分老于新石器文化堆积的器物年代,表明全新世高海面期砂质滨海相沉积的形成先于新石器人类活动遗迹。潮间带砂质滨海相沉积的上覆地层常在6.5 ka左右快速转变为潮上带的风成沉积-人类活动混合堆积,导致文化层中沉积物粒度分选变差,参数波动较大。淇澳岛小沙澳湾9―4.3 ka的滨海相砂质沉积的顶部目前位于海拔＋4.8 m,这一高程可能与构造抬升运动有关。     

Late Holocene dune migration on the south Texas sand sheet

There are a wide variety of vegetated, eolian depositional landforms associated with the south Texas sand sheet, attesting to the past dominance of eolian processes. Mapping identified two sets of parabolic dunes elongating with winds from the southeast and the northwest. Parabolic dunes elongated by northwesterly winds are older than ca. 200 years and may be associated with eolian depositional events ca. 2700 and/or 2000 years ago. The latest dune migration event, associated with southeasterly winds occurred ca. 200 years ago and at one site is inset into northwesterly-extended parabolic dunes. This period of dune migration may be coincident with particularly severe drought identified in the tree-ring record centered at AD 1790, when the Palmer Drought Severity Index was − 4. A threshold of dune movement may have occurred ca. in the 11th, 15th and 20th centuries when there are two or more consecutive years with a Palmer Drought Severity Index of < − 4, corresponding to 30–50% reduction in precipitation. Dune systems on Coastal Plain of Texas to reactivated repeatedly due to climate variability in the past 3000 years.     

Quantitative Holocene climatic reconstruction from Arctic Russia

Vegetation changes reflected in fossil pollen spectra are a primary source of information about climate fluctuations in the past. A statistical-information (transfer function) method based on the correlation of recent pollen spectra with modern climate conditions has been used to reconstruct Holocene climatic changes from fossil pollen. Climatic variables used for the reconstructions are the mean annual, January, July temperatures and annual precipitation. Peat sections with pollen and ¹⁴C data from the Arctic Russia were used for the reconstructions. The reconstructed climate fluctuations are similar to the climate changes obtained from many sites in the former USSR. A clear signal for Younger Dryas cooling, 11,000-10,000 yr BP and early Preboreal warming is apparent. The early Preboreal (10,000-9000 yr BP) was the warmest time for sites from modern coastal and island areas. The warm interval occurred in the Boreal period, about 8500 yr BP. According to the reconstructions the warmest time for non-coastal areas was the last half of Atlantic period, 6000-4500 yr BP. Other warm intervals were reconstructed about 3500 and 1000 yr BP. Reconstructions show that warming periods are primarily defined as times of increased summer temperatures, and cooling periods as time of decreased winter temperatures. The precipitation followed the temperatures: during the warming periods precipitation increased and during the cooling periods it decreased. Precipitation maximum, about 100 mm higher than present, are reconstructed for the warmest interval, 6000-4500 yr BP at all sites.     

小冰期福建海岸沙丘的沉积环境

选取福建东南沿海典型海岸沙丘——东海沙丘,运用GPR（Ground Penetrating Radar）技术探测海岸沙丘内部构造,辅助天然剖面和人工探槽观测,进行系统的年代采样与OSL（Optically Stimulated Luminescence）测年,并选择物理意义明确的粒度参数作为主要环境代用指标,获得了亚热带季风区砂质海岸带典型海岸沙丘的沉积年代和沉积结构。结果表明：（1）东海沙丘是由若干灌丛沙丘组成的横向沙丘,0～6 m主要是～0.45 ka BP以来形成的海岸风成沙丘,可以划分为～0.45 ka BP和0.22～0.12 ka BP两个阶段。（2）东海沙丘沉积过程是多因素共同作用的结果,冷干的气候环境是沙丘发育的适宜条件,入境台风频率增加可能加快了风沙的沉积过程。对比历史文献资料发现,气候异常期往往与社会动荡期、重要历史事件相对应。     

渭河流域东部全新世环境演变与古文化发展的关系研究

 在对渭河流域东部全新世黄土剖面磁化率、粒度、Rb/Sr、CaCO3等气候指标测定分析的基础上,结合已测定的光释光（OSL）年龄和古文化研究的最新成果,探讨了该区环境演变与人类古文化演进的历史及其相互关系。研究发现,在9.34~6.77 ka BP全新世最适宜的气候条件下,在7.80~7.30 ka BP出现了老官台文化,之后发育了仰韶早期文化;在全新世中期6.77~5.48 ka BP干冷气候初期出现了仰韶文化最繁荣的庙底沟类型文化;中后期随资源环境的持续恶化,该区出现了仰韶文化衰落的西王村类型文化;在全新世中晚期的5.48~3.12 ka BP气候再次发生好转推动了该区龙山文化的发展;4.60~3.76 ka BP期间频繁发生的洪水事件可能进一步强化了人地关系,并进而推动了该区文化进入夏商人类文明时期;3.12 ka BP以来趋于干冷的气候在推动该区人类文明进一步发展的同时,人类活动对环境影响的强度和范围也日益加大。渭河流域古文化得以延续发展至今,一方面说明气候环境的变化并未超越先民适应能力的范围,另一方面也说明渭河流域具有先民维持生存和发展的优越资源环境条件。     

Do swarms of migrating barchan dunes record paleoenvironmental changes? — A case study spanning the middle to late Holocene in the Pampa de Jaguay, southern Peru

Swarms of barchan dunes are common in arid environments. Unlike immobile or slowly moving dunes whose stratigraphy can be used to reconstruct paleoenvironmental changes, the high migration rate of barchans seems to prohibit their use as geoarchives. In this paper, a possible use of barchan swarms for paleoenvironmental reconstructions is presented. The approach is based on dune migration. In a case study based on 500 dunes in the Pampa de Jaguay aeolian transport corridor in coastal southern Peru, middle to late Holocene changes in the supply of aeolian material are inferred from calculating the time of dune initiation at the coastline. Limitations posed by the assumptions underlying this approach are discussed.     

海南岛现代风成岩(沙丘岩)的形成及其地貌意义

本文从沉积物结构、沉积结构特征以及胶结物类型等方面区别海岸沙丘岩、沙堤岩和海滩岩,并探讨了沙丘岩的形成机制及环境意义。     

古土壤记录的内蒙古沙区全新世环境变化

古土壤是发育于地质历史时期埋藏的自然土壤,是记录古环境信息的重要载体。本文基于对内蒙古沙区古土壤研究文献的梳理,通过古土壤测年数据统计,对比区内其他信息载体的研究成果,分析内蒙古沙区沙漠/沙地形成时代及全新世环境变化。结果表明:内蒙古沙区全新世环境变化可分为3个阶段:全新世早期（10～8.5 ka BP）为升温阶段,气候以干冷为主;全新世中期（8.5～2.5 ka BP）为气候适宜期,古土壤普遍发育,同时存在短期干冷波动;全新世晚期（2.5 ka BP以来）为降温期,气候逐步干冷,部分沙地气候波动频繁,形成古土壤。     

Relationships between Trophic State, Paleosalinity and Climatic Changes during the First Holocene Marine Transgression in Rocha Lagoon, Southern Uruguay

Paleolimnological data are presented on trophic development, climatic change and sea level variations in Rocha Lagoon, a 72 km² coastal lagoon in southern Uruguay. Using a sediment core that extended from 7000 to about 3700 yr BP, analyses of organic matter, carbonate, diatoms and chrysophyte cysts were used to track the early Holocene paleolimnological conditions of Rocha Lagoon. Opal phytoliths were also counted and identified, both temperature and humidity indices were calculated, and Opal Phytolith Association Zones (OPAZ) were identified by performing Principal Coordinates Analysis (PCO). Diatom Association Zones (DAZ) corresponding to marine/brackish and brackish/freshwater episodes were closely related to changes in trophic state. Those DAZ representing marine/brackish stages exhibited a lower trophic state than those DAZ dominated by brackish and freshwater diatoms. This highlights that during the first Holocene marine transgression, Rocha Lagoon did not continuously exhibit marine/brackish conditions as reported in previous papers. Instead, three brackish/freshwater episodes related to sea level variation and changes in humidity were identified. The first episode, by ~6000 yr BP, was related to sea level change as no significant changes in either temperature or humidity indices were observed. The second episode, between 5000 and 4400 yr BP, was related to both a sea level decrease and an increase in humidity, as a transition from humid to very humid climate was inferred. Concomitant decreases in salinity and increases in trophic state were also observed. The third episode, after ~4000 yr BP, was related to the end of the first Holocene regressive phase when sea level was slightly below present levels. Further decreases in salinity and increases in trophic state were detected. The paleoclimatic trends inferred in this study were in close agreement with other regional studies on climatic change, as cool temperatures were inferred. However, major changes in humidity were also detected. A humid to very humid climate was inferred for ~7000–4500 yr BP, but the occurrence of a semiarid/arid climate was inferred for ~4500–3700 yr BP. Our data suggest that during transgressive and regressive events there might be higher frequency and lower amplitude sea level oscillations that might lead to changes in salinity and trophic state of coastal aquatic systems. Such oscillations could only be tracked by high resolution analyses of sedimentary records and could be best interpreted with complementary data on paleoclimate. In addition, microfossils such as diatoms and opal phytoliths were shown to be very sensitive to such paleoenvironmental changes.