阿尔金山北麓晚新生代沉积物磁组构特征及其地质意义

阿尔金山北麓晚新生代沉积物比较敏感地记录了阿尔金山构造活动的历史.通过对若羌米兰河口剖面晚新生代沉积物沉积学和磁组构特征分析,发现中新世晚期以来该区地层沉积变化明显,岩石磁化率椭球体以压扁为主,磁面理发育,磁化率椭球体最小轴方向为NNE-SSW和NNW-SSE,推测阿尔金山晚新生代以来可能至少经历了中新世末-上新世初、晚上新世和中更新世三次重大构造活动历史.根据磁化率各向异性最小轴方向的变化,结合地层不整合关系、沉积物砾石成分和古水流方向变化以及区域研究成果,表明若羌一带地块晚上新世以来发生阶段性逆时针旋转,推断阿尔金断裂构造带的左走滑特征可能形成于晚上新世以后.     

北京平谷马坊Zk09钻孔新生代地层格架及其地质意义

本文基于北京平谷马坊地区Zk09钻孔新生代地层岩性岩相分析和沉积物古地磁等测试,建立了北京平原泃河水系中下游冲洪积区完整新生代地层格架。其中,0m～180m为中更新世-全新世陆相辫状河和曲流河沉积,180m～240.5m为中新世-上新世残坡积、湖积和三角洲前缘沉积。Zk09钻孔新生代不连续地层揭示了北京平原区两次重要的抬升构造事件：第一期构造事件发生于中新世,而不是前人研究认定的早更新世或上新世末,其最终结束了大渤海湾盆地古近纪盆-岭构造系统演化;第二次构造事件发生于中更新世早期,其可能是目前以走滑运动为主的最新构造变动形式起始时间。     

黄河、永定河发育历史与流域新生代古湖演变间的相互关系

据两河谷地两侧都有山麓侵蚀面存在,且侵蚀面上局部残存上新世古冲积物质,推断两河带形成时代不晚于上新世中早期。上新世末,随着流域出现内陆断陷湖盆,两河均由外流河变为内流河,即由外流期转为内流期。据最近在三门峡发现的哺乳动物化石,和泥河湾地区地层与年代学资料,内流期延续到早更新世末,或中更新世中期。此后,两河重新转入外流期,延续至今仍保持外流状态。     

Early Pliocene hominids from Gona, Ethiopia

Comparative biomolecular studies suggest that the last common ancestor of humans and chimpanzees, our closest living relatives, lived during the Late Miocene-Early Pliocene. Fossil evidence of Late Miocene-Early Pliocene hominid evolution is rare and limited to a few sites in Ethiopia, Kenya and Chad. Here we report new Early Pliocene hominid discoveries and their palaeoenvironmental context from the fossiliferous deposits of As Duma, Gona Western Margin (GWM), Afar, Ethiopia. The hominid dental anatomy (occlusal enamel thickness, absolute and relative size of the first and second lower molar crowns, and premolar crown and radicular anatomy) indicates attribution to Ardipithecus ramidus. The combined radioisotopic and palaeomagnetic data suggest an age of between 4.51 and 4.32 million years for the hominid finds at As Duma. Diverse sources of data (sedimentology, faunal composition, ecomorphological variables and stable carbon isotopic evidence from the palaeosols and fossil tooth enamel) indicate that the Early Pliocene As Duma sediments sample a moderate rainfall woodland and woodland/grassland.     

Geological and palaeontological context of a Pliocene juvenile hominin at Dikika, Ethiopia

Since 1999, the Dikika Research Project (DRP; initiated by Z.A.) has conducted surveys and excavations in badlands that expose Pliocene and Pleistocene sediments south of the Awash River in Ethiopia, between surrounding hominin localities at Hadar, Gona and the Middle Awash region. Here we report our geological mapping and stratigraphic measurement of the DRP area, and the context of a remarkably well-preserved skeleton of the earliest known juvenile hominin at the Dikika DIK-1 locality. Our mapping of the DRP area permits a complete definition of the hominin-bearing Hadar Formation and provides a cohesive structural and tectonic framework defining its relationships to adjacent strata. Our findings reveal the basin-scale tectonic, depositional and palaeoenvironmental history of the area, as well as a clear taphonomic and palaeontological context for the juvenile hominin. Such data are crucial for understanding the environmental context of human evolution, and can be integrated into larger-scale tectonic and palaeoenvironmental studies. Our basin-scale approach to palaeoenvironments provides a means to elucidate the complex geological history occurring at the scale of temporally and geographically controlled fossil point localities, which occur within the rich tectonic and depositional history of the Awash Valley.     

New hominin genus from eastern Africa shows diverse middle Pliocene lineages

Most interpretations of early hominin phylogeny recognize a single early to middle Pliocene ancestral lineage, best represented by Australopithecus afarensis, which gave rise to a radiation of taxa in the late Pliocene. Here we report on new fossils discovered west of Lake Turkana, Kenya, which differ markedly from those of contemporary A. afarensis, indicating that hominin taxonomic diversity extended back, well into the middle Pliocene. A 3.5 Myr-old cranium, showing a unique combination of derived facial and primitive neurocranial features, is assigned to a new genus of hominin. These findings point to an early diet-driven adaptive radiation, provide new insight on the association of hominin craniodental features, and have implications for our understanding of Plio-Pleistocene hominin phylogeny.     

Astronomically modulated late Pliocene equatorial Pacific climate transition and Northern Hemisphere ice sheet expansion

The equatorial Pacific underwent a significant climate transition during the late Pliocene, which is characterized by cooling of global sea surface temperatures (SSTs) and formation of a marked SST gradient between the eastern and western equatorial Pacific. Moreover, this transition was nearly synchronous with the late Pliocene Northern Hemisphere glaciation. Probing the relationship among solar insolation, low and high latitude processes is the key to unravel the mechanism of this climate transition. A se...     

A new hominin foot from Ethiopia shows multiple Pliocene bipedal adaptations

A newly discovered partial hominin foot skeleton from eastern Africa indicates the presence of more than one hominin locomotor adaptation at the beginning of the Late Pliocene epoch. Here we show that new pedal elements, dated to about 3.4 million years ago, belong to a species that does not match the contemporaneous Australopithecus afarensis in its morphology and inferred locomotor adaptations, but instead are more similar to the earlier Ardipithecus ramidus in possessing an opposable great toe. This not only indicates the presence of more than one hominin species at the beginning of the Late Pliocene of eastern Africa, but also indicates the persistence of a species with Ar. ramidus-like locomotor adaptation into the Late Pliocene.     

Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels

It is thought that the Northern Hemisphere experienced only ephemeral glaciations from the Late Eocene to the Early Pliocene epochs (about 38 to 4 million years ago), and that the onset of extensive glaciations did not occur until about 3 million years ago. Several hypotheses have been proposed to explain this increase in Northern Hemisphere glaciation during the Late Pliocene. Here we use a fully coupled atmosphere-ocean general circulation model and an ice-sheet model to assess the impact of the proposed driving mechanisms for glaciation and the influence of orbital variations on the development of the Greenland ice sheet in particular. We find that Greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene. By contrast, our model results suggest that climatic shifts associated with the tectonically driven closure of the Panama seaway, with the termination of a permanent El Ni?o state or with tectonic uplift are not large enough to contribute significantly to the growth of the Greenland ice sheet; moreover, we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the Earth's orbit.     

台湾海峡地形地质特征及其通道工程选线

台湾海峡地处太平洋板块和欧亚板块碰撞带的前沿,地壳活动强烈,地震也时有发生。海峡主体属台西盆地,西界为滨海断裂带,与闽浙隆起相邻。海峡中部主要断裂,包括晋江凹陷东界主断层(F2)和九龙江凹陷东南界主断层(F3),可能在晚上新世,甚至第四纪仍有活动。海峡南北部地形明显不同,北部地形走向为NE向,总体呈槽隆相间的格局,最大水深约90m;南部相对平坦,地形走向NS-NNW,最大水深68~70m。从拟选通道线附近的地震剖面来看,A、B、C三线附近海底均有断层,其中A、B两线F2断层明显,至少切到上新统顶界,甚至可能切入第四系;C线断层切至上新统顶界部,但主断层F3似止于上新统中部,第四纪后不再活动。台湾海峡的地震活动,南部强于北部。结合地形、地质条件、地震特征及设想隧道选线看,北线可能优于中线和南线。但由于现有资料不足以确定海底地质灾害的分布特征,建议对海峡进一步开展以工程地质、地质灾害为目的的中比例尺调查,为通道工程的科学选线提供依据。     

Late Cenozoic history of deep water circulation in the western North Pacific: Evidence from Nd isotopes of ferromanganese crusts

Despite its importance in regulating the global climate, the past deep ocean circulation in the western North Pacific has still been poorly understood. Nd isotopes of ferromanganese crusts have been proven to be a good proxy to monitor paleoceanic circulation changes. In this study, late Cenozoic Nd isotopic records are recovered from two ferromanganese crusts located near Mariana arc but at different water depths (MKD13: 1530 m, MDD53: 2700 m), and their implications for paleocirculation change in this area are explored. From the early to late Miocene, Nd isotopic compositions of MDD53 remained stable, and they were also characterized by the least radiogenic signatures ( Nd4.0 to5.0) compared to crusts of similar water depths in the Miocene North Pacific. Afterward, an abrupt increase in its Nd value occurred in the Pliocene. In contrast, Nd isotopes of MKD13 became more radio- genic with time in the Miocene and were almost invariable thereafter. The continual increase in Nd of shallower crust MKD13 is interpreted as reflecting progressive closure of Indonesian Seaway in the Miocene, while the deep western boundary current sourced from the Southern Pacific may have dominated Nd isotopes of deeper crust MDD53 during the same time interval. The lack of Nd isotopic variation of MKD13 in the Pliocene indicates that there were no changes in Nd sources in shallower waters and the final restriction between the Indian and Pacific may have only occurred since then. Therefore the observed large shift to more radiogenic Nd isotopes of MDD53 in the Pliocene should not be resulted from changes in vertical input from shallower to deeper water. Instead, a decreased ventilation of deep southern component current along the studied water depth range (~2700 m) may have continued in the Pliocene.     

Pollen evidence from Baode of the northern Loess Plateau of China and strong East Asian summer monsoons during the Early Pliocene

The red clay eolian sequence on the Chinese Loess Plateau (CLP) is an important archive for paleoclimate change from the late Miocene to Pliocene,and can provide significant information for the controversial problems of East Asian monsoon evolution and its forcing mechanism.In this study,we present a pollen record from Baode,northern CLP.The record shows four stages of paleoecological evolution.From 5.6-4.4 Ma,a forest steppe ecosystem developed under an extremely warm period with high seasonal precipitation.Since 4.4 Ma,a drier episode occurred,which prompted parkland landscapes to develop.During 3.5-3.05 Ma,the environment changed to a rather open steppe ecosystem with a much cooler and drier climate.After 3.05 Ma,the vegetation evolved to forest steppe.Using the percentages of arboreal plants to mirror precipitation,and comparing with other published pollen data from the CLP,we find the existence of S-N directionality of the precipitation change and high percentage of arboreal plants in the entire CLP during the Early Pliocene,which suggest the CLP was characterized by a strong East Asian summer monsoon.The strong summer monsoon corresponds well to the low global ice volume,which may illuminate global climate mechanism for the summer monsoon evolution in the early Pliocene.     

云南景谷盆地及陇川盆地新生代生物群特征及环境地质意义

通过对云南景谷盆地及陇川盆地新生代生物群特征的对比,探讨了新生代两大盆地环境演变:早中新世到上新世为湖盆发展期→湖盆扩大→萎缩期,气候为早期的干燥→中新世早期的温暖湿润→中新世中晚期的寒冷阴湿→上新世的干燥,而中新世中晚期湖盆的扩大形成的半深湖-深湖环境为油气的形成提供了有利条件。尽管两大盆地在沉积环境的演化上大体一致,但气候和沉积环境的演变和差异决定了两大断陷盆地生物面貌上的差异,从而直接控制了化石燃料形成的类型和质量     

First discovery of Promimomys （Arvicolidae） in East Asia

Promimomys asiaticus sp. nov., the first known species of the genus in East Asia, is described. The material was collected from the early Pliocene cave deposit in Dajushah Hill, Huainan, Anhui Province. Promimomys was first found in Europe and considered as the ancestor of the family Arvicolidae. The new species from China is distinct from the type species, P. cor, and other known species in its thicker enamel of uniform thickness, simple anterior loop of ml, and blunt, salient angles. It is more primitive than other known species in Europe and North America and also more primitive than Mimomys bilikeensis of early Pliocene of Inner Mongolia. It is thus the earliest and the most primitive arvicolid rodent known. The discovery of Promimomys asiaticus sp. nov. is significant to the study on the origin and the phylogeny of arvicolids, and to the discussion of the intercontinental dispersal events of arvicolids.     

柴达木盆地西部尕斯库勒盐湖周缘岩系和湖内沉积物含铀性模拟

 以柴达木盆地西部尕斯库勒盐湖周缘岩系和湖内沉积物为研究对象,通过淋滤实验和悬浮平衡模拟实验,探讨该盐湖不同物源的含铀性.分析表明,尕斯库勒盐湖周缘3 种岩系(老地层、上新世含盐岩系、第四纪沉积物)淋滤液水化学特征类似,且从淋滤液水化学特征可知该盐湖水化学具有明显的再溶盐特征;3 种岩系淋滤作用强烈,盐湖第四纪沉积物中的铀最容易被淋出,上新世含盐岩系中的铀次之,蚀源区岩石中的铀难淋出;悬浮平衡实验表明,悬浮液中铀含量随平衡时间增长呈现先迅速降低而后缓慢升高的变化趋势,而沉积颗粒物中铀含量变化趋势与悬浮液中铀含量刚好相反,说明铀在悬浮液和沉积颗粒物之间确实发生了交换,且交换速率较快;在平衡实验初期,悬浮液中铀含量快速降低的现象可能是悬浮液中的铀被固相吸附所致;不同时期铀的来源分析表明,在新近纪和第四纪早期,尕斯库勒盐湖内卤水和沉积物中的铀主要来自周边岩石的风化淋滤作用,铀补给量相对较少,而到了第四纪中、晚期,铀主要来自上新世含盐岩系风化淋滤和深部水补给,再加上沉积物和周边岩石化学风化,铀补给量相对前一时期大得多.     

Granite landform characteristics, distribution and evolution patterns in Huangshan Mt.

The various types of granite landforms in the Huangshan Mt. are distributed in a concentric pattern. The remaining parts of the planation surface are in the center; domical peaks, castle peaks, pointed peaks, and ridges are arranged from the center to the periphery accordingly. This reveals that knick points are still near the center and the center area is the common divide of the radial water system. It is inferred that the granite bodies in the Huangshan Mt. were exposed to erosion in Miocene and Pliocene, and the planation surface was also formed then. After the slight uplift in late Pliocene, a light-incised surface was formed. Then, in early Quaternary, there were intense uplifts and incisions so that deep incised surface was formed. The above process is still in progress, and results in high peaks and deep gorges outside of the center area. However, due to the limited catchment area in the center, headward erosion is mild, and the current landforms in the Huangshan Mt. can be maintained for a long time.     

Geology and fauna of a new Pliocene locality in north-western Kenya

Lothagam Hill reveals a succession of fossil bearing sediments that extend knowledge of the East African Pliocene back from the base of the Omo succession, to about 5.5 million years.     

Rapid denudation of the Himalayan orogen in the Nyalam area,southern Tibet,since the Pliocene and implications for tectonics–climate coupling

The Himalayan orogen characterized by very high variability in tectonic and climatic processes,and is thus regarded as a natural laboratory for investigating the coupling of tectonics and climate,as well as the influence of this coupling on geomorphological processes.This study uses apatite fission track(AFT)dating of samples from a45-km-long section crossing the Great Himalaya Crystalline Complex(GHC)in the Nyalam area,southern Tibet,to constrain the timing and rate of late Cenozoic denudation.The AFT ages can be divided into two groups:(1)15–6 Ma,to the north of Nyalam town,for which the bestfit line of elevation-age has a gentle slope of 0.05,and for which a denudation rate of 0.27 mm/a is calculated;and(2)3–1 Ma,south of Nyalam town,for which the best-fit line has a steep slope of 0.64,and for which a denudation rate of 1.32 mm/a is calculated.The whole AFT ages has a positive correlation with sample elevation(i.e.,older ages are found at higher elevations),and the geographical location of the point of inflexion of the two fitted lines corresponds closely to the junction of Poqu River near Nyalam town.By integrating the AFT data with thermotectonic modeling,it can be inferred that the GHC has experienced two different periods of denudation:(1)slow denudation during middle to late Miocene(15–6 Ma)is recorded in the northern part of the GHC;and(2)rapid denudation from the Pliocene to the Pleistocene(3–1 Ma)is recorded in the southern part of the GHC.An abrupt change in denudation rate occurred between the two periods,with the Pliocene–Pleistocene denudation rate being five times higher than that during the Miocene.This abrupt change in denudation rate during Pliocene pervaded the Himalayan orogen,and was roughly synchronous with a marked change in global climate at 4–3 Ma,and intensification of the Asian monsoon.Importantly,the later period of rapid denudation in the study region closely coupled to the mean annual precipitation,while there is no clear evidence for large-scale faulting activity and associated uplift during this period.Therefore,climate(precipitation)is inferred to be the main cause of the rapid denudation of the Himalayan orogen since the Pliocene.     

石油与中东现代化关系的经济学透视

分析单纯建立在石油工业基础上的中东经济存在着诸多的局限性,在一定程度上限定了该地区经济的发展特点及趋势。论证了石油在各产油国产业结构中比重过大使其经济结构失衡,各产业之间难以形成相互促进、相互扶持的态势。提出正确发挥其资源优势、改变其“病态”的经济状况并建立优化的经济结构、增强其整体的国际竞争力是中东经济未来的发展目标。