The Late Miocene climate response to a modern Sahara desert     

Arne Micheels  Jussi Eronen  Volker Mosbrugger 《Global and Planetary Change》2009,67(3-4):193-204

The climate cooling and vegetation changes in the Miocene/Pliocene are generally well documented by various proxy data. Some important ecosystem changes occurred at that time. Palaeobotanical evidence suggests that the Sahara desert first appeared in the Pliocene, whereas in the Miocene North Africa was green. In the present study, we investigate the Late Miocene climate response to the appearance of the Sahara desert from a climate modelling sensitivity experiment. We compare a model experiment, which includes a full set of Late Miocene boundary conditions, with another one using the same boundary conditions except that the North African vegetation refers to the present-day situation. Our sensitivity study demonstrates that the introduction of the Sahara desert leads to a cooling and an aridification in Africa. In addition, we observe teleconnection patterns related to the North African desertification at around the Miocene/Pliocene boundary. From our sensitivity experiment, we observe that the Sahara contributes to a cooling in Central Asia and in North America. As compared to hypsodonty data for Central Asia, an increased aridity is underestimated in the Sahara experiment. Finally, we observe that the introduction of the Sahara leads to a cooling in the northern high latitudes. Hence, our sensitivity experiment indicates that the appearance of the Sahara desert is one piece to better understand Late Cenozoic climate cooling being most pronounced in the high latitudes.  相似文献   

Neogene and Quaternary coexisting in the geological time scale: The inclusive compromise     

Brian McGowran  Bill Berggren 《Earth》2009,96(4):249-262

Removing the Tertiary and Quaternary Periods whilst conserving the Paleogene and Neogene Periods in The Geological Timescale 2004 caused a storm of protest. One response was to advocate restoring an enlarged Quaternary and consigning the Neogene to a minor role within the Tertiary. Amongst an array of practical, traditional, sentimental and anthropocentric reasons for this response, the one hard-core justification was that the rigidly nested hierarchy of the geological timescale must be preserved.The central objective of this paper is conserving the historically legitimate, Miocene-present, Neogene Period and System. There are two options for conserving the Quaternary concurrently with the Neogene: (i) an inclusive compromise in a flexible hierarchy, and (ii) an upgrading of Pliocene and Pleistocene divisions to the level of epoch.In the inclusive compromise there coexist alternative pathways through the hierarchical ranks. Thus geohistorians and biohistorians have two options for traversing the hierarchy from era to age, as in this example using the hierarchical positioning of the Calabrian Age and Stage:either Cenozoic [era]↔Neogene [period]↔Pleistocene [epoch]↔Calabrian [age],or Cenozoic [era]↔Quaternary [subera]↔Pleistocene [epoch]↔Calabrian [age].We reaffirm that the inclusive compromise is entirely viable. In so doing we (i) challenge the necessity of the rigidly nested hierarchy, which should be capable of a little flexibility; (ii) reject all analogies of the arbitrary and conventional chronostratigraphic hierarchy with three natural biological hierarchies; (iii) reaffirm the integrity of the Neogene extending to the present; and (iv) see no reason to doubt the harmonious coexistence of the two options preserving the Quaternary and Neogene traditions in an orderly working and stable time scale.In the alternative schema conserving the Neogene, divisions of the Pliocene and Pleistocene are upgraded, so that the Late Pleistocene, Early Pleistocene and Late Pliocene Epochs comprise the Quaternary Subperiod, itself equivalent to Late Neogene. The inflexibly nested hierarchy is preserved but the Tertiary is lost.  相似文献   

Mediterranean Neogene stratigraphy: development and evolution through the centuries     

MARIA BIANCA CITA 《Sedimentology》2009,56(1):43-62

  相似文献   

Geochemistry and petrology of selected coal samples from Sumatra, Kalimantan, Sulawesi, and Papua, Indonesia   总被引：4，自引：1，他引：3  

Harvey E. Belkin  Susan J. Tewalt  James C. Hower  J.D. Stucker  J.M.K. O'Keefe 《International Journal of Coal Geology》2009,77(3-4):260-268

Indonesia has become the world's largest exporter of thermal coal and is a major supplier to the Asian coal market, particularly as the People's Republic of China is now (2007) and perhaps may remain a net importer of coal. Indonesia has had a long history of coal production, mainly in Sumatra and Kalimantan, but only in the last two decades have government and commercial forces resulted in a remarkable coal boom. A recent assessment of Indonesian coal-bed methane (CBM) potential has motivated active CBM exploration. Most of the coal is Paleogene and Neogene, low to moderate rank and has low ash yield and sulfur (generally < 10 and < 1 wt.%, respectively). Active tectonic and igneous activity has resulted in significant rank increase in some coal basins. Eight coal samples are described that represent the major export and/or resource potential of Sumatra, Kalimantan, Sulawesi, and Papua. Detailed geochemistry, including proximate and ultimate analysis, sulfur forms, and major, minor, and trace element determinations are presented. Organic petrology and vitrinite reflectance data reflect various precursor flora assemblages and rank variations, including sample composites from active igneous and tectonic areas. A comparison of Hazardous Air Pollutants (HAPs) elements abundance with world and US averages show that the Indonesian coals have low combustion pollution potential.  相似文献   

第四系的正式地位和定义初步确定     

彭善池 《地层学杂志》2009,33(3)

国际地层委员会最新表决通过第四系为系级年代地层单位,它位于新近系之上,底界由意大利西西里岛的Monte San Nicola"金钉子"定义,也就是由定义格拉斯阶底界的"金钉子"来定义,年龄值约为2.59Ma;更新统的底界也下移到这个位置,格拉斯阶划归更新统,长期争论的第四系的地位和定义问题有望得到解决。  相似文献   

柴达木盆地东北部新近纪构造旋转及其意义   总被引：4，自引：1，他引：3  

杨用彪  孟庆泉  宋春晖  胡思虎  张平  刘平  陈传飞 《地质论评》2009,55(6):775-784

青藏高原东北缘构造变形的研究是认识高原隆起过程、机制和印度—欧亚板块碰撞远程效应的重要途径。柴达木盆地是印度－欧亚板块碰撞后南北向挤压应力为动力背景的高原东北部内陆盆地,沉积物主要来自于周边山地,完整的保存了新生代以来高原隆升的详细记录。通过柴达木盆地东北部瑙格剖面精细古地磁及构造旋转研究发现,20.1～15.1Ma以及15.1～8.2Ma柴达木盆地分别发生了9.7°±7.4°和6.4°±4.4°的顺时针旋转,约8.2Ma后,柴达木盆地东北部瑙格地区发生了16°±7.5°的逆时针快速旋转。通过分析认为,前两次的顺时针构造旋转事件可能与阿尔金断裂的左旋走滑有关。而约82Ma以来的逆时针旋转事件属于柴达木盆地东北部瑙格地区的局部旋转,可能与温泉断裂的右旋走滑有关,说明青藏高原东北部在昆仑山、阿尔金山和祁连山三条巨型断裂系左旋相对运动的宏观控制下形成的NNW向温泉右旋走滑断裂开始走滑的年代为约8Ma。  相似文献   

新近纪以来中国构造演化特征与天然气田的分布格局   总被引：19，自引：1，他引：18  

王庭斌 《地学前缘》2004,11(4):403-416

中国地处三大板块间的三角地带 ,是世界上新近纪以来构造运动活跃地区之一 ,与油气成藏及保存条件相关的主要特征是 :(1)在西部 ,古老造山带的重新活跃 ,在其前缘形成前陆盆地及逆冲构造 ,新近纪以来的急剧沉降、快速沉积 ,促进了深部源岩有机质的演化进程 ,也为生物气藏的形成创造了有利的地质条件 ;(2 )多期次的构造热事件及高热流值促进了有机质的快速演化、成藏 ,以及异常高压及泥拱等特殊构造的形成 ;(3)多期次构造运动为油气的快速运聚、幕式充注成藏提供了优质输导系统 ,为超晚期快速成藏提供了储聚场所 ;(4 )大断裂、岩浆及深部热流体的活动 ,不仅促进有机成因油气藏的形成 ,也是无机成因气的主要释放和聚集时期。新近纪以来构造演化特征在西部影响最广泛 ,也最深刻 ,形成的前陆盆地是中国重要天然气聚集区之一 ,是这些盆地本部气藏最终形成、定型时期 ,并在造山带内形成了近百个小型断陷盆地 ,形成了新的油气勘探领域。在中部 ,是四川盆地所有气田最终的形成、定型时期 ;在鄂尔多斯盆地促进了靖边至乌审旗地区天然气进一步富集。在东部 ,渤海海域形成一批大中型油气田 ,促进了其他盆地 (坳陷 )不同成因气藏的形成 ;在近海海域 ,既促进了有机成因气藏快速形成 ,也促进了无机成因非烃气藏以及无?  相似文献   

阿尔金新近纪红黏土粒度特征及古气候记录     

黄丹青  杨利荣  李建星  岳乐平  潘峰  徐永  张余波 《沉积学报》2019,37(2):309-319

为反演阿尔金新近纪红黏土记录的古气候、古环境信息,在已有的磁性地层学约束基础之上对剖面的粒度指标进行了系统的分析,并利用粒度端元模型(EMM)进行分解。结果表明,可分为三个粒度端元:端元1(众数粒径5.2μm)众数粒径集中分布于2～6μm,与北太平洋西风带粒度分布和中国黄土细粒组分的粒度分布相似;端元2(众数粒径20μm)呈负偏态非对称分布,众数粒径在32～16μm之间,为低空西风所搬运短距离做跃移运动的粉尘物质;端元3为双主峰分布,众数粒径57μm和2.5μm,代表着尘暴事件中风动力近源变化强度,反映混合沉积特征。其中在10.8～10.3 Ma、8～6 Ma、5.2～4.3 Ma、3.6～2.8 Ma端元1粒度含量呈减小趋势,端元2粒度百分含量呈逐渐增加趋势,中值粒径增大。13～2.6 Ma阿尔金红黏土记录显示内陆干旱化加剧事件经历了10.8～10.3 Ma、8～6 Ma、5.2～4.3 Ma、3.6～2.8 Ma四个阶段,结合前人对该剖面及邻区其他地质环境记录研究表明,亚洲内陆干旱化可能的起始时间为11 Ma左右,西风环流在本区占主导地位。全球变冷是内陆干旱化加剧的主导要素,青藏高原的阶段性隆升起着推动作用。  相似文献   

Tectonostratigraphic framework and depositional history of the deepwater Ulleung Basin,East Sea/Sea of Japan     

Kyoung-Jin Kim  Dong-Geun Yoo  Nyeon-Keon Kang  Bo-Yeon Yi 《Basin Research》2020,32(4):613-635

The Ulleung Basin, East Sea/Japan Sea, is a Neogene back-arc basin and occupies a tectonically crucial zone under the influence of relative motions between Eurasian, Pacific and Philippine Sea plates. However, the link between tectonics and sedimentation remains poorly understood in the back-arc Ulleung Basin, as it does in many other back-arc basins as well, because of a paucity of seismic data and controversy over the tectonic history of the basin. This paper presents an integrated tectonostratigraphic and sedimentary evolution in the deepwater Ulleung Basin using 2D multichannel seismic reflection data. The sedimentary succession within the deepwater Ulleung Basin is divided into four second-order seismic megasequences (MS1 to MS4). Detailed seismic stratigraphy interpretation of the four megasequences suggests the depositional history of the deepwater Ulleung Basin occurred in four stages, controlled by tectonic movement, volcanism, and sea-level fluctuations. In Stage 1 (late Oligocene through early Miocene), syn-rift sediment supplied to the basin was restricted to the southern base-of-slope, whereas the northern distal part of the basin was dominated by volcanic sills and lava flows derived from initial rifting-related volcanism. In Stage 2 (late early Miocene through middle Miocene), volcanic extrusion occurred through post-rift, chain volcanism in the earliest time, followed by hemipelagic and turbidite sedimentation in a quiescent open marine setting. In Stage 3 (late middle Miocene through late Miocene), compressional activity was predominant throughout the Ulleung Basin, resulting in regional uplift and sub-aerial erosion/denudation of the southern shelf of the basin, which provided enormous volumes of sediment into the basin through mass transport processes. In Stage 4 (early Pliocene through present), although the degree of tectonic stress decreased significantly, mass movement was still generated by sea-level fluctuations as well as compressional tectonic movement, resulting in stacked mass transport deposits along the southern basin margin. We propose a new depositional history model for the deepwater Ulleung Basin and provide a window into understanding how tectonic, volcanic and eustatic interactions control sedimentation in back-arc basins.  相似文献   

新近纪海相生物地层事件年龄新编   总被引：14，自引：2，他引：12  

李前裕  Lucas LOURENS  汪品先 《地层学杂志》2007,31(3):197-208

介绍新近纪海相生物地层研究的新进展。2004年新的"国际地质年代表"以405ka偏心率长周期为基础来划分新近纪的主要地层界线,标志着轨道地层学时代的到来。新生代包括E1—E162偏心率长周期,底界的年龄为65.5±0.3Ma,其中新近纪有E1—E58周期,底界年龄为23.03Ma,并且根据天文调谐得出一系列新的古地磁年龄和生物事件年龄。由于这些新年龄,特别是接近新近纪底部的年龄与早期结果相差0.5Ma或更大,所以将其汇总介绍,以求与当前国际研究保持同步衔接,增强海洋新近纪高分辨率地层工作的准确性。  相似文献