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1.
Trend of climatic changes in geological history of the Earth was determined by gradual decrease in the global surface temperature. Substantial deviations from this trend depended on the prevalent type of volcanism: predominantly explosive volcanism at convergent boundaries between lithospheric plates led to cooling and onset of glacial epochs, while intense intraplate volcanism strengthened greenhouse effect and resulted in global warming. During cold epochs, orogenic processes played an important role in climatic variations. The most frequent and regular climatic variations are controlled by the Earth position in solar orbit (Milankovitch cycles). The Late Cenozoic variations of cold climate were interrelated with orogenic processes caused by collision between the Indian and North Asian lithospheric plates. The first event of considerable cooling in the Northern Hemisphere (2.8–2.5 Ma ago) coincided with a rapid growth of mountains throughout the collision belt. The Tibetan Plateau formed in South Asia. In Central Asia, the large (> 1.5 × 106 km2) Khangai-Altai-Sayan mountain system appeared 3 Ma ago. Total area subjected to orogenic processes in Central and South Asia exceeded 9 × 106 km2. The intense intraplate volcanism suggests that sublithospheric mantle was involved into orogenic processes. Alternation of glacial and interglacial climatic epochs during the last 1.8 m.y. is recorded in Central Asia. These climatic variations are compatible with the Milankovitch cycles. As is established, climatic events recognizable in the Baikal sedimentary record are correlative with interglacial and glacial epochs detectable in volcanic lavas of the East Sayan Mountains. There are indications of lava eruptions into ice during the cold periods. It is assumed therefore that all the cooling epochs detectable in the Baikal sedimentary record after 1.8 Ma were associated with development of mountain glaciation that formed glacial sheet up to 3 km thick and 100 000 km2 in size. During the Brunhes Chron, there were eight glaciations at least. The endogenic (volcanism and orogeny) and exogenic (glaciation) processes during the last 3 m.y. are shown to be correlative. The intermittent development and degradation of thick ice sheets was responsible for oscillation of lithospheric load on the asthenosphere, and this caused periodical magma generation in marginal parts of volcanic provinces. 相似文献
2.
KRISTEN E. K. ST. JOHN LAWRENCE A. KRISSEK 《Boreas: An International Journal of Quaternary Research》2002,31(1):28-35
Analysis of a Miocene-Pleistocene ice-rafted debris (IRD) record from the western Irminger Basin provides evidence for the initiation and long-term behavior of the SE portion of the Greenland Ice Sheet. In the late Miocene (~7.3 Ma), IRD supply to Ocean Drilling Program site 918 increased significantly indicating that glaciers large enough to reach sea level were present in SE Greenland long before the onset of widespread Northern Hemisphere glaciation. IRD accumulated at this site throughout the Pliocene and Pleistocene, supporting the hypothesis that SE Greenland was a key nucleation area for the formation of the Greenland Ice Sheet. Since glacial onset, the western Irminger Basin IRD record is characterized by a succession of episodes with high IRD mass accumulation rates (MARs). The site 918 IRD record indicates that greatest iceberg production in SE Greenland occurred during major climatic transitions (e.g. widespread Northern Hemisphere glacial expansion at 2.7 Ma and the mid-Pleistocene climate shift at 0.9 Ma), and that SE Greenland sometimes also led the northern North Atlantic region in glacial response to climatic forcing (e.g. glacial intensification at ~4.8 and, along with NE Greenland, at ~3.5 Ma). 相似文献
3.
The null hypothesis: globally steady rates of erosion,weathering fluxes and shelf sediment accumulation during Late Cenozoic mountain uplift and glaciation 总被引：1，自引：0，他引：1 
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下载免费PDF全文 At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from equilibrium arise from the transient response of landscape denudation to climatic and tectonic perturbations. We posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium persists at the global scale over millions of years, as has been proposed for late Cenozoic erosion. We synthesize weathering fluxes, global sedimentation rates, sediment yields and tectonic motions to show a remarkable constancy in the pace of Earth‐surface evolution over the last 10 Ma and support the null hypothesis – that global rates of landscape change have remained constant over this time period, despite global climate change and mountain building events. This work undermines the hypothesis that increased weathering due to mountain building or climate change was the primary agent for a decrease in global temperatures. 相似文献
4.
宇宙成因核素~(10)Be揭示的北祁连山侵蚀速率特征 总被引：1，自引：0，他引：1
山脉侵蚀速率的大小和时空分布信息是研究山脉构造—气候相互作用和地貌演化的关键切入点,其大小是受气候还是构造控制争论已久。宇宙成因核素10Be方法为从千年至万年尺度上定量研究流域平均侵蚀速率提供了一种先进和快捷的技术手段,为揭示侵蚀速率与现代气候和构造地貌因子的关系并进行相关分析提供了基础。利用该方法对北祁连山近现代侵蚀速率进行了研究。所采集的9个流域现代河沙样品,结合前人数据进行共同分析,结果显示该区侵蚀速率的变化范围为18.7~833 mm/ka,北祁连山中段的侵蚀速率约为323 mm/ka,该区侵蚀速率与降雨量没有明显的对应关系,但与流域平均坡度呈现很好的非线性关系,揭示坡度是该区侵蚀速率的最主要控制因素。通过对比北祁连山地表平均侵蚀速率和该区域的断层垂直滑动速率发现整体上该区域地表侵蚀速率要低于祁连山北缘断层的垂直滑动速率,反映了北祁连山正处于地形抬升和生长的过程之中。 相似文献
5.
Optically Stimulated Luminescence dating, grain-size analysis and magnetic susceptibility measurements were conducted on the Fanjiaping loess section, from the western Chinese Loess Plateau. The results confirm that last glacial high-frequency climatic shifts were documented in mid-latitude continental archives. The grain-size record indicated that coarse-grained sediments with horizontal bedding and channel-fill structures were only deposited in several short intervals, equivalent to the beginning of marine oxygen isotope stage (MIS) 4 and the early to middle MIS 3. This probably implies brief rainfall intensification of the Asian summer monsoon, and its disappearance since the late MIS 3 to MIS 2 may have been a response to significant glacial cooling in the Northern Hemisphere. Previous investigations revealed high sea-surface temperatures at high latitudes at the start of MIS 4, and the early to middle MIS 3 intensification of summer insolation in the Northern Hemisphere, implying evident climate amelioration. Climate improvement favors boreal forest recovery, enhancing both winter and summer air temperatures. The resultant smaller equator-polar temperature gradient probably helped the moisture-laden summer monsoon to penetrate northward. This study thus provides new significant information about the response of terrestrial loessic palaeoenvironments to millennial-timescale climatic fluctuations during the last glacial period. 相似文献
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7.
天山山脉隶属中亚造山带,晚新生代时期印度板块向亚洲板块俯冲的构造效应同样影响到天山地区,使这一晚古生代形成的造山带重新复活。天山南北两侧的晚第三纪和第四纪时期的地层正是对印度板块-亚洲板块碰撞带的响应,发生构造变形,形成了一系列逆冲断层和褶皱,指示这一区域的地壳在晚新生代变短和加厚。文章对天山北缘晚中新世以来的沉积进行了详细的磁性地层学和沉积学研究,结果表明:在研究的独山子背斜地区,磨拉石沉积最早出现于约7百万年前,说明天山山脉自7百万年前开始有一次构造隆升,研究区内7.00~2.58Ma间的巨厚砾石沉积主要是构造抬升的结果。而早更新世的西域砾岩沉积在很大程度上与第四纪时期全球冰期的来临,特别是北半球开始发育大规模冰川作用有关,因此西域砾岩应当是在第四纪冰川作用(气候变冷)及新构造运动共同作用下的产物。 相似文献
8.
The Whippoorwill Formation is a gleyed diamicton that is present locally within bedrock depressions beneath the oldest glacial till in northern Missouri, USA. Stratigraphy, paleomagnetism, and cosmogenic-nuclide burial ages show that it was deposited between the Matuyama-Gauss magnetostratigraphic boundary at 2.58 Ma and the first advance of the Laurentide ice sheet into Missouri at 2.47 ± 0.19 Ma. High cosmogenic-nuclide concentrations also show that the constituents of the Whippoorwill Formation experienced long exposure at a stable landscape surface with erosion rates of 1-2 m/Ma. However, cosmogenic-nuclide concentrations are invariant with depth below the Whippoorwill Formation surface, indicating active mixing of the soil profile shortly before burial by till. The Whippoorwill Formation retains numerous features indicative of cryoturbation. Therefore, we interpret it as a buried Gelisol, a soil formed under periglacial conditions in the presence of permafrost. At the onset of Northern Hemisphere glaciation, climate cooling established permafrost conditions and accelerated erosion by inducing landscape instability. Thus, weathered regolith materials were mobilized and redeposited by gelifluction shortly before the ice sheet overrode the landscape. 相似文献
9.
《Quaternary Science Reviews》2007,26(3-4):312-321
Based on a radiocarbon and paleomagnetically dated sediment record from the northern Red Sea and the exceptional sensitivity of the regional changes in the oxygen isotope composition of sea water to the sea-level-dependent water exchange with the Indian Ocean, we provide a new global sea-level reconstruction spanning the last glacial period. The sea-level record has been extracted from the temperature-corrected benthic stable oxygen isotopes using coral-based sea-level data as constraints for the sea-level/oxygen isotope relationship. Although, the general features of this millennial-scale sea-level records have strong similarities to the rather symmetric and gradual Southern Hemisphere climate patterns, we observe, in constrast to previous findings, pronounced sea level rises of up to 25 m to generally correspond with Northern Hemisphere warmings as recorded in Greenland ice-core interstadial intervals whereas sea-level lowstands mostly occur during cold phases. Corroborated by CLIMBER-2 model results, the close connection of millennial-scale sea-level changes to Northern Hemisphere temperature variations indicates a primary climatic control on the mass balance of the major Northern Hemisphere ice sheets and does not require a considerable Antarctic contribution. 相似文献
10.
国外景观演化研究的最新进展 总被引：5，自引：0，他引：5
景观演化与全球构造、生物演变和主要气候变化具有相同的时间尺度 ,是长期全球变化的一个重要方面。最近 ,地表过程在地壳变形中的作用已经引起了广泛的注意 :一方面努力从景观中模拟地形演化或演绎地壳过程 ;另一方面试图通过地壳变形和地表过程的型式和速度来研究隆起、海平面变化、侵蚀、气候和地势之间的动力学关系。文中旨在介绍和评述国外关于会聚边缘和裂开边缘山脉尺度景观演化研究 ,包括高原边缘地形演化、前陆盆地的沉积型式、景观切割、古地形复原以及质量流动和平衡等方面的最新进展 ,以及地表过程和地壳过程相互作用中的反馈机制、均衡效应和岩石圈强度效应以及调整和平衡等几个理论问题。目前已经普遍认为 ,把地表过程纳入地球动力学模型之中 ,无疑对于认识造山带的发育和裂开边缘的演化是一个巨大的进步。 相似文献
11.
《Sedimentology》2018,65(2):517-539
Enhanced aridification of Central Asia driven by the combined effects of orogenic surface uplift, Paratethys retreat, changes in atmospheric moisture transport and global cooling is one of the most prominent Cenozoic climate change events of the Northern Hemisphere. Deciphering regional long‐term patterns of Central Asian hydrology is, therefore, a key element in understanding the role of Northern Hemisphere mid‐latitude drying in the global hydrological system. This study characterizes long‐term palaeoenvironmental conditions between the late Oligocene and early Miocene in south‐eastern Kazakhstan based on stable isotopes, elemental geochemistry and laser ablation uranium–lead geochronology from alluvial, fluvial and pedogenic deposits. Sedimentary facies and geochemical weathering indices suggest an increased surface and groundwater discharge fed by orographically enhanced precipitation in the Tien Shan hinterland. In contrast, pedogenic stable isotope data and elevated rates of magnesium fixation in clay minerals mirror enhanced rates of evaporation in the vadose zone due to protracted aridification. This study posits that pronounced surface uplift of the Tien Shan Mountains during the Oligocene–Miocene transition promoted regionally increased orographic precipitation and the development of fluvial discharge systems. 相似文献
12.
JUAN PEDRO RODRÍGUEZ‐LÓPEZ CARLOS L. LIESA JAN VAN DAM PALOMA LAFUENTE LUIS ARLEGUI LOPE EZQUERRO POPPE L. DE BOER 《Sedimentology》2012,59(5):1536-1567
An aeolian dune field migrating to the east encroached on the toes of alluvial fans in the Teruel Basin (eastern Spain) during a short interval in the Late Pliocene (ca 2·9 to 2·6 Ma), when Northern Hemisphere glaciation and strong glacial–interglacial cycles began. Preservation of the dune field was controlled by syn‐sedimentary activity of a normal fault. Ephemeral water discharge eroded aeolian sands and formed V‐shaped channels in which aeolian sandstone blocks accumulated. The incorporation of loose aeolian sand in wadi waters modified the sediment/water ratio, changing the physical properties of the flows as they penetrated the aeolian dune field. The erosion and cover of aeolian dune foresets by sheetflood deposits suggest that dune‐damming caused the intermittent ponding of water behind the dunes and its flashy release. The arid climate in the Late Pliocene western Mediterranean realm favoured the transport of windblown sediments from northern Africa and western Mediterranean land masses into the Mediterranean. The formation of the studied aeolian dune field (2·9 to 2·6 Ma) and possibly others (for example, the Atacama, Namib and Sahara deserts) correlates with a strong increase of the influence of obliquity, which can be attributed to the combination of a regional expression related to the reduced effect of precession due to a minimum in the long‐period (2·3 Ma) eccentricity cycle and a remote expression of the onset of the Northern Hemisphere glaciation. 相似文献
13.
Michael R. Kaplan Daniel C. Douglass Bradley S. Singer Robert P. Ackert Marc W. Caffee 《Quaternary Research》2005,63(3):636-315
At Lago Buenos Aires, Argentina, 10Be, 26Al, and 40Ar/39Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000–16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/103 yr, both yield a common estimate age of 150,000–140,000 yr for the two moraines. The erosion rate estimate derives from 10Be and 26Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded 40Ar/39Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation. 相似文献
14.
V.B. Bazarova L.M. Mokhova M.A. Klimin L.A. Orlova K.Yu. Bazarov 《Russian Geology and Geophysics》2008,49(12):978-985
Climatic changes in southeastern Transbaikalia in the Middle and Late Holocene and their influence on alluvial sedimentation environments are reconstructed from the results of study of the Ilya floodplain sediments (Alkhanai National Park). At the beginning of the Subboreal period, the regional climate became more arid, which led to a significant increase in steppe species communities in the landscapes. Intense climate aridization also took place at the beginning and at the end of the Subatlantic period of the Holocene. The alluvial-sedimentation rate increased during the weakening of aridization and decreased during cooling and the intensification of aridization. The obtained regional data are compared with data on the adjacent areas and the global climatic changes in the Northern Hemisphere. 相似文献
15.
第四纪气候变化机制研究的进展与问题 总被引：3，自引：1，他引：3
自从20世纪50年代海洋沉积氧同位素记录被揭示以来,经典的陆地4次冰期理论被新的认识所取代,人们发现第四纪以来冰期—间冰期旋回远远不止4次,并且从深海沉积和陆地黄土获取的古气候变化记录与地球轨道参数变化可以对比,为揭示第四纪古气候变化机制构建了明确的框架。近年来有关末次冰期不稳定气候事件的揭示也为深入认识古气候变化特征提供了新的证据。然而冰期—间冰期旋回机制、南北半球在冰期—间冰期循环过程中的耦合机制以及气候不稳定事件发生机制仍然是困扰古气候研究者的重大问题。 相似文献
16.
Time-dependent effects of heat advection and topography on cooling histories during erosion 总被引：9，自引：0，他引：9
Both erosion and surface topography cause a time-dependent variation in isotherm geometry that can result in significant errors in estimating natural exhumation rates from geochronologic data. Analytical solutions and two-dimensional numerical modelling are used to investigate the magnitude of these inaccuracies for conditions appropriate to many rapidly exhumed mountain chains of rugged relief. It is readily demonstrated that uplift of the topographic surface has a negligible effect on the cooling history of an exhumed rock sample and cannot be quantified by current geochronologic methods. The topography itself perturbs the isotherms to a depth that depends on both the vertical and horizontal scale of the surface relief. Estimations employing different isotopic systems in the same sample with higher closure temperatures (> 200°C) are not generally influenced by topography. However, direct conversion of cooling rates to exhumation rates assuming a simple constant linear geotherm markedly underestimates peak rates, due to variation of the geothermal gradient in time and space and to the time lag between exhumation and cooling. Estimations based on the altitude variation in apatite fission-track ages are less prone to such inaccuracies in geothermal gradient but are affected by near-surface time-dependent variation in isotherm depth due to advection and topography. In tectonically active mountain belts, high exhumation rates are coupled with rugged topography, and exhumation rates may be markedly overestimated, by factors of 2 or more. Even at lower exhumation rates on the order of 1 mm/a, the shape of the cooling curve is modified by advection and topography. A convex-concave shape to the cooling curve does not necessarily imply a change of exhumation rate; it may also be attained by a more complicated geothermal gradient induced by topographic relief. Very fast cooling below 100°C, often interpreted as reflecting faster exhumation, can be more simply explained by the lateral cooling effect of topographic relief, with samples exhumed in valleys displaying a different near-surface cooling history to those on ridge crests. 相似文献
17.
Daniel Ariztegui María Martha Bianchi Julieta Masaferro Eric Lafargue Frank Niessen 《第四纪科学杂志》1997,12(4):333-338
Several high-resolution continental records have been reported recently in sites in South America, but the extent to which climatic variations were synchronous between the northern and southern hemispheres during the Late-glacial–Holocene transition, and the causes of the climatic changes, remain open questions. Previous investigations indicated that, east of the Andes, the middle and high latitudes of South America warmed uniformly and rapidly from 13 000 14C yr BP, with no indication of subsequent climate fluctuations, equivalent, for example, to the Younger Dryas cooling. Here we present a multiproxy continuous record, radiocarbon dated by accelerated mass spectroscopy, from proglacial Lake Mascardi in Argentina. The results show that unstable climatic conditions, comparable to those described from records obtained in the Northern Hemisphere, dominated the Late-glacial–Holocene transition in Argentina at this latitude. Furthermore, a significant advance of the Tronador ice-cap, which feeds Lake Mascardi, occurred during the Younger Dryas Chronozone. This instability suggests a step-wise climatic history reflecting a global, rather than regional, forcing mechanism. The Lake Mascardi record, therefore, provides strong support for the hypothesis that ocean–atmosphere interaction, rather than global ocean circulation alone, governed interhemispheric climate teleconnections during the last deglaciation. © 1997 John Wiley & Sons, Ltd. 相似文献
18.
Travertine deposits are important records of past fluid flow in the Earth's crust, and document fluid migration through both tectonic activity and changes in climate. While many studies hint at possible relationships between travertine formation and global climate, none have investigated these connections on a global scale. Here we compile 1649 published travertine ages from six continents to test the hypothesis that global and/or regional changes in climate regulate travertine deposition. Peaks in bedded travertine ages occur with main frequencies that correspond to 100‐kyr changes in global climate, where most peaks occur during glacial terminations or interglacial periods, including a large peak that coincides with the Early Holocene climatic optimum. Time–series analysis also suggests a possible connection with 41‐kyr obliquity cycles. At regional scales, many peaks also correspond with local times of high precipitation or wet conditions. This can be attributed to higher groundwater recharge rates, providing the necessary water to form travertine. Many bedded travertine‐depositing systems may therefore be water‐limiting and sufficient CO2 may be present even during times of no travertine deposition. Exceptions to this conclusion are banded vein travertine deposits, which typically form during times of dry climate when water tables are low. Copyright © 2019 John Wiley & Sons, Ltd. 相似文献
19.
新生代构造抬升对地表化学风化和全球气候变化的影响 总被引：9，自引：0，他引：9
全球新生代构造抬升 ,特别是南亚喜马拉雅青藏高原和南美安底斯山脉和Altiplano高原在新生代的抬升对地表化学风化和全球气候变化产生了重要影响。它对地表化学风化的影响主要表现为引起造山带地区化学风化能力的提高 ;而它对全球气候变化的影响则主要表现在两个方面 ,一是直接的物理影响 ,即通过对大气和海洋循环的影响来对大气变化产生作用 ;一是通过对地表硅酸盐岩石的化学风化造成大气CO2 变化和全球温度的改变 ,从而对气候变化产生间接的生物化学效应。目前看来 ,新生代构造抬升造成的大气CO2 浓度减少是造成全球新生代气候变冷的重要原因。这已得到了近 10年来计算机大气环流模型 (GCMs)数值模拟和野外实验研究的支持 ,但在关于地表化学风化的主要控制因素 ,以及海洋Sr同位素是否可作为反映地表化学风化速率变化的替代性标志和气候变化反馈机制等方面 ,还需要作进一步研究。 相似文献
20.
《Quaternary Science Reviews》2005,24(14-15):1547-1557
Correlation of paleoclimatic evidence with orbital changes shows that the build-up of polar ice accelerated when low obliquity coincided with perihelion in Northern Hemisphere winter. Under low obliquity the insolation was channeled to the tropics at the expense of both polar caps. As perihelion moved from winter solstice toward spring equinox, the solar beam in astronomic winter and spring became stronger than in summer and autumn. This orbital configuration under climate conditions like today would lead to warming of tropical oceans but cooling of the polar regions. The areally weighted global mean surface temperature, which is dominated by the low latitudes, would increase. Consequently, during the first millennia, the early glacial ice build-up was most likely accompanied by global warming. It was the associated increase of meridional insolation and temperature gradients, which were instrumental in the transition to a glacial.A significant part of the current global warming is due to the gradual temperature increase of the tropical oceans. As the changing orbital configuration today resembles that of the last interglacial/glacial transition, the warming is likely to have a natural component. 相似文献