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| 新生代特征地质时期的古地理重建及其在古气候模拟中的初步应用 | |
| 其他题名 | Palaeogeography reconstructions for typical geologic periods during the Cenozoic and their preliminary applications in paleoclimate modelling |
| 郭庆春 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 刘晓东 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 特征地质时期的古地理环境是基于气候模式进行古气候模拟研究必不可少的构造边界条件。新生代以来地球的古地理环境发生了巨大变化，如大西洋的持续扩张、太平洋的收缩、特提斯海的退缩、印度板块和澳大利亚板块的向北快速漂移、南极和北极冰盖的形成、安第斯山、落基山、青藏高原等地形隆升等，这些古地理变化对全球气候和环境演化产生了深刻的影响，因而了解过去的古地理状况对于全面理解地球气候与环境变迁至关重要。古气候模拟是研究过去气候变化机制的重要手段，建立地质时期的构造边界条件是古气候模拟所必须的一项基础性工作，这些边界条件包括大陆位置、地形、海洋深度（海深）等。鉴于此，文本重建了新生代特征地质时期的古地理，并利用重建的边界条件初步进行了相关时期的气候数值模拟。现将本文的主要内容和结论概括如下：（1）基于大陆漂移说、海底扩张学说、全球板块构造、地质力学等理论，采用全球板块软件Gplates、海岸线基础数据集（Global EarthByte Gplates Coastlines）、Gplates全球板块旋转模型（Global plate rotation model），通过模型运算，输出古新世中期（60Ma）、始新世晚期（40Ma）、渐新世晚期（25Ma）和中新世晚期（10Ma）四个特征地质时期的初始海陆分布，然后通过系统收集、整理和分析已发表的相关文献和网站的古地图等信息，对海陆分布历史进行重新评估，采用地理信息系统（GIS）软件据此对海岸线进行矢量化和拓扑处理，并对初始海陆分布进行了修正，重建了新生代四个特征地质时期的海陆分布。最后利用Gplates软件将古生物化石数据 (http://paleodb.org)分别旋转到10Ma，25Ma，40Ma，60Ma，验证了重建的新生代四个特征地质时期古大陆和古海洋位置的合理性，古生物数据也为约束印度次大陆和欧亚大陆碰撞时间提供了新证据。（2）重建的新生代四个特征地质时期海陆分布主要特征如下：古新世中期（60Ma）印度次大陆较现今位置偏南，澳大利亚板块较现今位置偏南，塔斯曼海峡和德雷克海峡（Drake passage）较现今狭窄，而白令海峡（Bering Strait）关闭，特提斯海（Tethys Sea）、西伯利亚海（Siberian Sea）、图尔盖海峡（Turgai strait）、印度尼西亚通道（Indonesian passage）和巴拿马通道（Panama Gateway）非常广阔；大西洋（Atlantic Ocean）面积比现今面积小，太平洋面积比现今面积大。始新世晚期（40Ma）与古新世中期相比，印度板块和亚洲板块发生碰撞，印度次大陆和澳大利亚板块继续向北移动，美洲继续向西移动，大西洋（Atlantic Ocean）扩大，太平洋继续缩小；而非洲继续向东北移动。渐新世晚期（25Ma）与始新世晚期相比，印度和澳大利亚继续北移，副特提斯海（Paratethys）和古地中海（Mediterranean Tethys）较40Ma狭小；西伯利亚海（Siberian Sea）和图尔盖海峡（Turgai strait）关闭。中新世晚期（10Ma）与渐新世晚期相比，印度和澳大利亚继续北移，副特提斯海（Paratethys）退缩，古地中海面积减小。（3）采用Gplates软件和全球板块旋转模型，把已有ETOPO2、15Ma、45Ma地形和海深，旋转到40Ma、25Ma、10Ma，然后通过GIS软件进行空间运算，叠加到重建的海陆分布之上，并对海深数据进行了修正，得到初始古地形和重建古海深。然后依据已发表文献、古植物古高程计、稳定同位素古高程计等定量古高程计以及定性替代指标，综合不同方法与指标重新评估了古地形演变历史，对初始古地形进行修正，得到三个新生代特征地质时期的重建古地形，并通过大量文献资料进行了验证。鉴于青藏高原隆升历史存在很大争议，不同代替指标恢复的古高度有很大差异，特把青藏高原分为喜马拉雅地块、拉萨地块、羌塘地块、松潘-甘孜地块和昆仑地块、柴达木-祁连地块五个地块，依据高原分块特征以及我们收集整理的新生代青藏高原古高度点和文献资料，对古高度及古纬度进行重新评估，重建了三个特征地质时期的青藏高原古高度和古纬度，并通过GIS融合到全球古地形中。并通过大量上地壳变形历史、断层开始活动时间、海相沉积结束时间、区域性冷却事件时间等定性替代指标验证了高原演化历史。（4）重建的新生代三个特征地质时期古地形主要特征如下：始新世晚期（40Ma）安第斯山非常低，而落基山古地形与现今高度接近，帕米尔高原大约为现今高度的40%，喜马拉雅地块接近海平面，而拉萨地块和羌塘地块隆升到较高海拔地形，松潘-甘孜地块和昆仑地块、柴达木-祁连地块与帕米尔高原地形相对较低。渐新世晚期（25Ma）落基山古高度比40Ma低，安第斯山和格陵兰古高度较低，南极大约为现今高度的一半，喜马拉雅地块地形较低，拉萨地块和羌塘地块继续隆升，海拔较高，松潘-甘孜地块和昆仑地块、柴达木-祁连地块、帕米尔高原隆升高到一定高度。中新世晚期（10Ma）地形已与现今地形比较接近，地球上的主要山脉和高原包括落基山、安第斯山、伊朗高原、青藏高原、帕米尔高原、天山、蒙古高原和南极大陆等。（5）古新世中期（60Ma）气候数值模拟研究表明，亚洲中纬度大部分地区为西风控制，东亚季风环流系统还没有建立，而60Ma印度北部季风环流系统已经建立。亚洲大陆南部和东部大部分地区为干旱-半干旱区，原因可能是亚洲南部和东部被高压控制，降水难以形成；亚洲大陆西部出现高降水中心，亚洲中部40°N-60°N范围内年降水量超过800mm，可能是由于西伯利亚海和图尔盖海峡存在的结果。印度北方降水量远远超过了800mm，为湿润区，原因主要是印度北部基本为季风控制。各种地质记录也表明古新世期间亚洲南部和东部大部分地区为干旱-半干旱气候，气候较温暖，和模拟结果基本一致。 |
| 英文摘要 | Palaeogeographical environment in typical geologic periods is essential tectonic boundary conditions for palaeoclimate modelling. Great changes have happened in palaeogeographical environment of the earth during the Cenozoic, such as continual expansion of Atlantic, Pacific and Tethys Sea shrinkage, rapid northward drifts of Indian plate and Australian plate, formation of Antarctic and Arctic ice caps, topographic uplift of Andes, Rocky mountains and the Tibetan Plateau. These palaeogeographical changes have a profound impact on global climate and environment evolutions. Thus, conditions of palaeogeography are very important for understanding global climate and environment changes. Palaeoclimate modelling is an important study method for exploring climate change mechanism, and a fundamental task for palaeoclimate modelling is reconstruction of tectonic boundary conditions, which include continental position, palaeotopography, paleobathymetry and so on. In this study, therefore, palaeogeography of the earth for typical geologic periods during the Cenozoic is reconstructed and the relevant paleoclimate modelling is carried out by using our reconstructed boundary conditions. The main results are summarized as follows:(1) Based on the theory of continental drift, sea-floor spreading, global plate tectonics, geological mechanics and so on, initial land-sea distributions at the Middle Paleocene (60 million years, 60Ma), the Late Eocene (40Ma), the Late Oligocene (25 Ma), the Late Miocene (10Ma) are produced by using Gplates (desktop software for the interactive visualisation of plate-tectonics), Global EarthByte Gplates Coastlines and the global plate rotation model. Then through systematic collection, collation and analysis of published literature and palaeomap information from websites, the initial land-sea distributions are evaluated and modified by using the geographic information system (GIS) software based on vectorization and topology processing of the coastline. Finally, the land-sea distributions for typical geologic periods during the Cenozoic is reconstructed. In addition, using Gplates software, fossils data (http://paleodb.org) is respectively rotated to 10Ma, 25Ma, 40Ma and 60Ma to verify reconstructed paleo-continent and paleo-sea locations for four typical geologic periods during the Cenozoic. Fossils data also provides new evidence for time constraints of collision between Indian subcontinent and Eurasian continent.(2) The main features of reconstructed land-sea distributions for four typical geologic periods during the Cenozoic are as follows: at the Middle Paleocene (60 Ma), the positions of Indian subcontinent and Australia were located in the south of their current positions; Tasman passage and Drake passage (60Ma) was narrower than today; Tethys Sea, Siberian Sea, Turgai strait, Indonesian passage and Panama Gateway were very broad; Bering Strait was closed; Atlantic area was smaller than the current area, and the Pacific area was larger than the current area. Compared with the Middle Paleocene, at the Late Eocene (40 Ma), Indian plate collides with Asian plate; Indian subcontinent and Australia continued to move northward; America continued to move westward; Atlantic continued to expand; Pacific continued to shrink; and Africa continued to move to the northeast. Compared with the Late Eocene, at the Late Oligocene (25 Ma) Indian subcontinent and Australia continued to move northward; Paratethys and Mediterranean Tethys were narrower than 40 ma; Siberian Sea and Turgai strait was closed. Compared with the Late Oligocene, at the Late Miocene (10Ma) India and Australia further moved northward, Paratethys retreated, and Mediterranean area reduced.(3) Topography and bathymetry that are available from ETOPO2, 45Ma and 15Ma are respectively rotated to to 40Ma, 25Ma and 10Ma by using Gplates software and the global plate rotation model, and they are added to our reconstructed land-sea distributions through space operations of GIS software. Then paleobathymetry is modified, and initial paleotopography and paleobathymetry are reconstructed. Based on published literature, fossil plants, stable isotope paleoaltimetry and various qualitative indexes, paleotopography evolution history is reappraised by using comprehensive methods and indexes. Initial paleotopography is modified to obtain finally reconstructed paleotopography for typical geologic periods during the Cenozoic, then it is verified by a large number of literature data. The history of Tibetan Plateau uplift has a great controversy, and the relevant paleoelevations are different between various indexes and regions. So, the Tibetan Plateau is divided into five terrances including the Himalaya terrane, Lhasa terrane, Qiangtang terrane, Songpan-Ganzi-Kunlun terrane, and Qaidam-Qilian terrane to reappraise the paleoelevation and paleolatitude of the plateau. Based on our comprehensive integration, paleoelevation and paleolatitude of the Tibetan Plateau for three typical geologic periods during the Cenozoic is reconstructed, and integrated into global topography. Our reconstructions of the Tibetan Plateau topography is verified through a large number of information such as deformation history of upper crust, the beginning of fault, the end time of marine deposits, regional cooling event time and other qualitative indexes.(4) The main features of reconstructed paleotopography for three typical geologic periods during the Cenozoic are as follows: at the Late Eocene (40Ma), Andes was very low, but Rocky mountain was close to the present, Pamir was about 40% of today's topography, Himalayan terrane was close to sea level, while Lhasa terrane and Qiangtang terrane uplifted to higher altitude, Songpan-Ganzi terrane, Kunlun terrane , Qaidam-Qilian terrane and Pamir terrain was relatively low. At the Late Oligocene (25 Ma), Rocky mountain was lower than 40 Ma, Andes and Greenland was low, Antarctic was about half of elevation of today, Himalayan terrane was low, Lhasa terrane and qiangtang terrane was high and continue to uplift, Songpan-Ganzi terrane, Kunlun terrane, Qaidam-Qilian terrane and Pamirs plateau uplifted to certain elevation. Palaeotopography at the Late Miocene (10Ma) was similar with the current topography. The main mountain and plateau on earth include Rocky mountain, Andes, Iran plateau, Tibet plateau, Pamir, Tianshan, Mongolia plateau, and Antarctica, etc. (5) A preliminary numerical simulation of climate at the Middle Paleocene (60Ma) is conducted based on our reconstructed boundary conditions. The results show that the Middle Paleocene climate are quite different with the present-day. Most parts of mid-latitude regions of Asia are controlled by prevailing westerlies, and East Asia monsoon circulation system has not been established, though northern India monsoon has been appeared. Most parts of South Asia and East Asia is dry and semi-arid regions. The possible reason may be that the sub-tropical high pressure controls Southern Asia and East Asia, restraining the formation of precipitation; There is a precipitation center in West Asia, and annual precipitation of Central Asia 40°N-60°N is more than 800mm. That may be due to the existence of Siberian Sea and Turgai Strait. Precipitation in northern India as a humid area is far more than 800mm. The main reason is that northern India was basically controlled by monsoon in the mid-Paleocene. All kinds of the geologic records also show that most parts of South Asia and East Asia are arid and semi-arid climate during Paleocene. Our simulation results are generally consistent with geologic records. |
| 中文关键词 | 新生代 ; 古地理 ; 海陆分布 ; 青藏高原 ; 重建 ; 地理信息系统 ; 古气候模拟 |
| 英文关键词 | Cenozoic paleogeography land-sea distribution Tibetan Plateau reconstruction Geographic Information System paleoclimate modelling |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 环境科学 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287668 |
| 推荐引用方式 GB/T 7714 | 郭庆春. 新生代特征地质时期的古地理重建及其在古气候模拟中的初步应用[D]. 中国科学院大学,2016. |
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