中国山西张村上新世气候与海拔的初步研究     

秦锋  杨健  李金锋  刘海明  王宇飞 《地学前缘》2010,17(5):345

基于前人山西榆社盆地张村植物大化石和花粉组合资料,运用分布区叠加分析法,初步重建了山西张村上新世气候参数值和古海拔高度。研究结果表明,由不同数据来源计算的张村古气候参数数值变化范围大多落在今天的暖温带到北亚热带区间;依据原地埋藏的植物大化石组合推出上新世时山西张村地区存在植被垂直分带,周围为山地地形,由此估测的古湖海拔高程范围在400～1 000 m,明显低于今天约1 043 m的海拔高度,表明在上新世之后位于黄土高原东缘的张村地区还有抬升;支持前人关于更新世以来晋东南地区的整体缓慢抬升的推测。  相似文献   

Late-Quaternary miliolite (biogenic carbonate) deposits and their implications for sea-level fluctuations and climatic variability     

A. Durga Prasad  Falguni Bhattacharya  Gaurav Chauhan  D. Balaji  M.G. Thakkar  Y. Srinivasa Rao 《地球表面变化过程与地形》2021,46(5):921-941

The western coast of India (Kachchh) has ubiquitous preservations of Quaternary carbonate deposits popularly known as “miliolites”. Field-based detail documentation of the nature and distribution of miliolites supported by sedimentology and scanning electron microscopy (SEM) microtextural studies indicates that the miliolites were primarily deposited by wind as aeolinites and are termed “primary miliolites (PM)”. These were subsequently fluvially eroded and deposited and such deposits are termed “secondary miliolites (SM)”. The PM are dated between 28 ka to 16 ka largely clustering around the Last Glacial Maxima (LGM). In comparison, the fluvially reworked SM occurs as valley-fill deposits and were deposited episodically during 23 ka to 10 ka before present. Climatically, the deposition of PMs suggests enhanced aridity whereas SMs represent episodic strengthening of the Indian Summer Monsoon (ISM). The bedding attitudes of the PMs indicate that they were deposited predominantly by the northeasterly winds whereas the presence of the deflation lag deposits suggests downwind migration of sands during the equilibrium condition (reduced sediment supply). The aeolian parameters (based on the grain size and wind velocities) for PMs indicate high shear velocity (~23 to 48 cm⁻¹) and high transport rate (< 0.1 to 0.2 g/cm s). The short average flying distance implies that the biogenic sands were transported in multiple pulses (from coast to inland) at rates varying from ~200 m/h to ~1 km/h. Comparing our data with related occurrences along the biologically productive coasts in the mid-latitudinal belt indicates that the regional/global aridity during the lowered sea level was responsible for inland occurrences of aeolinites, particularly during the LGM. The strengthened northeast monsoon winds during the LGM was conducive to upwelling and production of biogenic carbonates along the coasts. The subsequent reworking of the aeolinites were mainly the results of local variability in precipitation.  相似文献   

3.50Ma BP以来河北衡水地区古植被与环境演化     

范淑贤  刘海坤  徐建明  郑宏瑞  赵华  毕志伟  杨振京  林防  张静 《现代地质》2009,23(1)

依据河北衡水南张庄600 m深HS1钻孔中529块岩心样品的孢粉分析,结合古地磁、光释光测试建立的年代地层格架,初步建立了河北平原中部衡水地区3.50 Ma BP以来孢粉组合的更迭序列。在3.50~2.58 Ma BP期间,研究区沉积环境稳定,主要是极浅水泛滥平原与浅湖相沉积,孢粉不丰富,孢粉组合结构简单,反映降水、气温等变化幅度小,气候由温暖湿润逐渐过渡到冷干;2.58~0.78 Ma BP期间,植被出现频繁波动,我国东部古季风气候格局已经基本形成,表现出气候频繁变化的不稳定性,具有早期温和偏干、中期温暖湿润、晚期温凉偏干的气候演化特征;780~15 ka BP期间,孢粉带组成成分较为丰富且复杂,在不同时期乔木植物与草本-灌木植物互为消长、相互更迭,反映气候变化幅度大、频率高的特点;15 ka BP至今,气候总体表现为干,其波动频率较快,植被属森林和草原兼而有之的类型。  相似文献   

Relict rock glaciers as indicators of Mediterranean palaeoclimate during the Last Glacial Maximum (Late Würmian) in northwest Greece     

P. D. Hughes  P. L. Gibbard  J. C. Woodward 《第四纪科学杂志》2003,18(5):431-440

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Late Devensian and Holocene palaeoecology and palaeoenvironments of the Morrone Birkwoods,Aberdeenshire, Scotland     

Brian Huntley 《第四纪科学杂志》1994,9(4):311-336

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Grain-size cycles in Salawusu River valley since 150 ka BP     

ZHANG Yu-hong  LI Bao-sheng  JIN He-ling  David Dian ZHANG  YAN Mun-cun  ZHU Yi-zhi  YAO Chun-xia 《地理学报》2001,11(4):461-472

The palaeo-mobile dune sands and fluvio-lacustrine facies with palaeosols in Milanggouwan stratigraphic section of the Salawusu River valley situated at the southeast of the Mu Us Desert experienced abundant remarkable alternative changes of coarse and fine rhythms in grainsize since 150 ka BP, and the grain-size parameters — Mz,σ, Sk, Kg and SC/D also respond to the situation of multi-fluctuational alternations between peak and valley values. Simultaneity the grainsize eigenvalues — Φ5, F16, Φ25, Φ50, Φ75, Φ84 and Φ95 are respondingly manifested as greatly cadent jumpiness. Hereby, the Milanggouwan section can be divided into 27 grain-size coarse and fine sedimentary cycles, which can be regarded as a real and integreted record of climate-geological process of desert vicissitude resulted from the alternative evolvement of the ancient winter and summer monsoons of East Asia since 150 ka BP.  相似文献   

贺兰山北段晚石炭世晚期和早二叠世早期植物群古生态学的研究   总被引：1，自引：0，他引：1  

陈丛林  史晓颖  张兴国 《现代地质》2001,15(4):355-361

在综合研究了贺兰山北段晚石炭世晚期和早二叠世早期植物群的特征和性质的基础上 ,对此植物群进行了古生态学方面的分析研究。采用了传统的埋藏学研究模式 ,对不同地区植物化石分别进行了埋藏学的研究 ,得出本区植物群的主要埋藏类型为原地埋藏 ,其次为亚原地埋藏 ,有极少量为异地埋藏。其化石群落基本能反映当时植物群的生活面貌 ,再结合分异度的数据恢复了古群落。此外 ,根据植物群的特征分析 ,得出当时的古气候应为赤道低纬度地区的热带雨林气候  相似文献   

Palaeoclimatic inferences from upper Palaeozoic siltstone of the Earp Formation and equivalents, Arizona-New Mexico (USA)     

GERILYN S. SOREGHAN  REW M. MOSES  MICHAEL J. SOREGHAN  MICHAEL A. HAMILTON†  C. MARK FANNING‡  PAUL K. LINK§ 《Sedimentology》2007,54(3):701-719

The Late Palaeozoic configuration of Pangaea contributed to a palaeoclimatic extreme that was characterized by both icehouse and monsoonal conditions. This study uses sedimentological, geochemical, and provenance data from silty facies of the Earp and equivalent Supai Formations (Arizona, New Mexico) to shed light on atmospheric circulation and glacial–interglacial climate change in westernmost equatorial Pangaea. Five silt‐rich facies comprise both loessite and marine and fluvially reworked loessite. An initial aeolian origin for the silt is indicated by the remarkably invariant grain size and the laterally continuous, sheet‐like geometry of beds. The silt‐rich facies occur in repetitive facies associations (1–20 m scale) that form mixed continental‐marine (loess, marine‐reworked loess), shallow‐marine, and continental (loess, palaeosol) ‘sequences’. Facies repetitions of both mixed continental‐marine and shallow‐marine sequences reflect a linked glacioeustatic–glacioclimatic control, whereas the continental (loess–palaeosol) couplets reflect a primary glacial–interglacial climatic cyclicity linked to glacioeustasy. Stratigraphic interpretations suggest that aeolian silt flux maximized during glacial to incipient interglacial stages (lowstand to early transgression), and decreased significantly or ceased during interglacials (highstand to early falling stage). Detrital‐zircon geochronological data indicate a transition from dominantly north‐easterly winds during the Middle Pennsylvanian to north‐westerly and south‐easterly winds by the Early Permian, which trend is inferred to reflect the onset of monsoonal circulation in western Pangaea. Relative grain‐size data support the detrital‐zircon data, and exhibit a significant decrease from the Sedona arch/Central Arizona shelf (north) to the Pedregosa basin (south) sections. Whole‐rock geochemical data suggest a relatively unweathered source for the silt in the north, and detrital‐zircon data indicate significant silt was derived from the local basement. These large piles of silt(stone) preserve valuable information for reconstructing both long‐term evolution in atmospheric circulation and short‐term fluctuations in glacial–interglacial climate. Many such indicators for long have been applied to ‘recent’ (Plio‐Pleistocene) loess, but are equally applicable to ‘deep‐time’ strata.  相似文献   

柴达木盆地自然伽玛曲线在古气候及沉积环境研究中的应用   总被引：6，自引：2，他引：6       下载免费PDF全文

杨平  陈晔  刘泽纯 《古地理学报》2003,5(1):94-102

应用自然伽玛测井（GR）曲线反演古气候和古环境的方法在国际上逐渐得到重视并取得了进展，柴达木盆地第四纪应用其反演2.85Ma B.P来的古气候变化也取得了成功。本文以柴达木盆地侏罗系冷科1井和雨33井自然伽玛曲线并结合孢粉等地质资料进行了古气候与沉积环境分析，证明GR曲线是有价值的古气候研究参数。GR值的大小及古气候的干湿变化和沉积水体的深浅变化均有内在联系，GR曲线振幅与频率的变化快慢反映出沉积环境动荡与稳定的相对特征，据此对两口井的沉积环境演变作了具体分析。结合古气候与沉积环境综合分析，GR曲线的异常波动还具有特殊的指相意义。GR值增大-古气候加湿-沉积水体加深的同步表现特征是一般性规律，构造-古地理背景的变动可改变这一对应关系，因而提供了研究古地理演变的信息，进一步丰富了GR曲线研究的地质涵义。说明在侏罗纪古气候和古环境研究上，GR曲线是一有价值的参考指标。  相似文献   

PALAEOCLIMATOLOGICAL SURVEY OF STALAGMITES FROM COASTAL AREAS IN TANZANIA   总被引：1，自引：0，他引：1  

KATARINA LUNDBLAD  KARIN HOLMGREN 《Geografiska Annaler: Series A, Physical Geography》2005,87(1):125-140

ABSTRACT. The aim of this study was to assess the potential of Tanzanian stalagmites as palaeoclimatic archives. Twelve stalagmites were collected in cave systems in the coastal areas. U-series dating, combined with published ¹⁴C-data, shows that one of the stalagmites was precipitated during the latter half of the latest glacial, between approximately 39 and 27 ka. Stable isotope analysis results indicate millennial-scale fluctuations in atmospheric CO₂ level during that time; and these fluctuations show a pattern very similar to that of the δ¹⁸O variations in the GRIP and Byrd ice-cores. The other stalagmites analysed turned out to be too porous and/or contained too much detritus to allow for reliable U-series dating. Due to low uranium content, the precision of the dating results is generally also poor. Samples from the five most compact and clean specimens yielded ages from c. 105 ka to c. 17 ka, though sometimes with an inverse age stratigraphy, indicating that the stalagmite precipitates were partly not compact enough to prevent post-depositional uranium leakage.  相似文献