排序方式： 共有10条查询结果，搜索用时 437 毫秒
1
1.
定量重建贵州梵净山一万年以来的植被与气候 总被引：8，自引：0，他引：8
在孢粉分析和＾１４Ｃ测定年龄资料的基础上，以现代梵净山植被带及其气候状况为类比系统，应用主成分分析方法，定量重建贵州梵净山１万年以来的古植被和古气候演化历史，将其分为三个阶段：１０－７．８ｋａＢ．Ｐ．，７．８－２．７ｋａＢ．Ｐ．和２．７ｋａ Ｂ．Ｐ到现在，依次为升温期，高温期和降温期、其中高温期年平均温度比现代年平均温度高出１．６－３．３℃。１万年以来的年降水量比较稳定，使本地区一直处于较湿润状态 相似文献
2.
论中国东部第四纪冷期植被与环境 总被引：8，自引：0，他引：8
在第四纪的冷期,中国东部华北和东北植物区,因深受干旱因素影响,广泛发展了草原植被。当时在欧亚大陆上,草原、森林草原和苔原可能曾自南欧一直分布到东亚。在南方植物区,亚热带针叶林曾在平原和丘陵广为分布。同时,许多喜湿热的类群则被保存于避难所中。由此看来,第四纪寒冷气候南侵到中国东部的强度和范围,是有限的。 相似文献
3.
John S. Armstrong-Altrin Yong Il Lee Richard H. Worden 《Chemie der Erde / Geochemistry》2009,69(1):45-60
The carbon, oxygen, and strontium isotope compositions of carbonate rocks from the upper Miocene Kudankulam Formation, southern India, were measured to understand palaeoenvironment and carbonate diagenesis of this formation. Both carbon and oxygen isotope ratios of various carbonate phases including whole rocks, ooids, molluscan mold-fill and sparry pore-fill calcite cements are depleted in 18O and 13C compared to those of contemporaneous seawater, indicating that the Kudankulam carbonates underwent extensive meteoric diagenesis. Based on δ13C and δ18O values for sparry calcite cements (pore-fill and molluscan mold-fill) formed in the meteoric diagenetic realm (δ13C from −7.8‰ to −6.0‰ and −9.0‰ to −7.0‰; δ18O from −9.2‰ to −6.5‰ and −9.4‰ to −2.6‰, respectively), it is interpreted that the diagenetic system was open and was proximal to the vadose water recharge zone. The negative δ18O values of various carbonate components (about −9.4‰ to −4.1‰ for whole rocks; about −8.4‰ to −2.6‰ for ooids) suggest that during the late Miocene the paleoclimate of the study area was humid, unlike today, probably due to the intense Indian monsoon system. The carbon isotope compositions (−7.9‰ to −3.6‰ for whole rocks; −4.9‰ to −1.5‰ for ooids) are consistent with the interpretation that the paleo-ecosystem comprised a significant proportion of C4 type plants, supporting a scenario of expansion of C4 plants during the late Miocene in the Indian subcontinent as far south as the southern tip of India. The 87Sr/86Sr ratios of the Kudankulam carbonates (0.70920 to 0.72130) are much greater than those of the contemporaneous or modern seawater (between 0.7089 and 0.7091) and show a general decrease up-sequence. Such high Sr isotope ratios indicate significant radiogenic 87Sr influx to the system from the Archean rocks exposed in the drainage area, implying that the deep-seated Archean rocks were already exposed in southern India by the late Miocene. 相似文献
4.
华北地台北部晚石炭世古植被演替及其古气候解释 总被引：2，自引：0，他引：2
拴马桩煤系植物化石研究结果表明，华北地台北部晚石炭世的古植被在维斯发期和斯蒂芬期之交发生了重要变化：斯蒂芬期以前，种子蕨类占主导地位，随后是以Ｐｅｃｏｐｔｅｒｉｓ为代表的树蕨真蕨类植物和有节类成了植被的主要类群。这种型式的古植被改变不仅与华北晚古生代植物群成分在本溪组与太原组界线上出现的真蕨类、有节类＂新生峰点＂相一致，而且与欧美基本植被在维斯发Ｄ期－斯蒂芬期的改组大体吻合。据叶相及煤中的碳同位素分析，晚石炭世晚期存在一个古气候升温事件。上述古植被的改组可能是这个升温事件的正反馈。 相似文献
5.
《China Geology》2022,5(3):439-456
This study identified two palynological assemblages, namely Bayanhuasporites-Cycadopites-Protoconiferus and Cicatricosisporites-Cedripites-Perinopollenites, in the Tongbomiao Formation in the Hongqi Sag in the Hailar Basin, Inner Mongolia, China for the first time. The former is distributed in the lower part of the Tongbomiao Formation and is characterized by abundant gymnosperm pollen and diverse fern spores. Among them, the gymnosperm pollen is dominated by Paleoconifer (4.98%–31.62%) and Cycadopite (8.55%–25.23%) pollen grains and also includes other pollen grains such as Classopollis, Parcisporites, Erlianpollis, Callialasporites, and Jiaohepollis. The fern spores in the former palynological assemblage contain Bayanhuasporite (0–8.96%), Granulatisporites (0.93%–6.97%), and some important Cretaceous genera, such as Cicatricosisporites, Concavissimisporites, Densoisporites, Hsuisporites, Foraminisporis, and Leptolepidites. The Cicatricosisporites-Cedripites-Perinopollenites palynological assemblage is distributed in the upper part of the Tongbomiao Formation. Gymnosperm (77.30%), Pinaceae (31.9%), and Paleoconiferus (19.02%) pollen predominate this palynological assemblage, and Quadraeculina, Erlianpollis, and Jiaohepollis pollen are also common in this assemblage. The fern spores in this palynological assemblage include abundant Cicatricosisporites (4.29%). Besides, Concavissimisporites, Aequitriradites, and Leptolepidites are also common in this palynological assemblage. No angiosperm pollen has been found in both palynological assemblages. The identification of both palynological assemblages provides important evidence for the biostratigraphic correlation between the Hailar Basin and its adjacent areas. It also enables the reconstructions of the Berriasian-Valanginian (Early Cretaceous) vegetation and the paleoclimate on the eastern Mongolian Plateau during 141–132 Ma. The vegetation reconstructed on the palynological data of the represented by Hailar Basin in eastern Mongolian Plateau (141.6–141.4 Ma), form conifer forest or conifer broad-leaved mixed forest to conifer forest with shrubs and grassland, the climate belongs to warm temperate and warm-subtropicalt, the highest temperature is estimated to reach 35–38°C. Form 132.3 Ma, the vegetation type is conifer forest, and its paleoclimate is sub-humid warm temperate, the highest temperature is estimated to reach 24–29°C.©2022 China Geology Editorial Office. 相似文献
6.
呼伦湖、乌伦古湖全新世植物群发展与气候环境变化 总被引：7，自引：0，他引：7
于１９９０－１９９３年分别对呼伦湖及乌伦古湖进行了调查，并对其剖面及钻孔进行了孢粉分析，结合＾１４Ｃ测年、介形类、硅藻分析资料，对两区孢粉植物群演替、气候与湖泊环境变迁进行了比较。结果表明，１０．０ｋａＢ．Ｐ．前，西北地区湖水位变化与冰川融水有关，东北湖区温凉湿润气候受季风环境影响所致；１０．０－７．０ｋａＢ．Ｐ．及５．０－３．０ｋａＢ．Ｐ．间，气候干旱，两者受西风带控制；７．０－５．０ｋａＢ．Ｐ 相似文献
7.
8.
上海地区更新世孢粉组合及其古植被,古气候 总被引：17，自引：1，他引：16
通过对上海地区三个钻孔更新世沉积物的孢粉研究,首次结合最优分割、对应分析等计算机数量统计手段,划分出了九个孢粉组合带,反映了该区植被演替、气候波动的九个阶段;丰富了本地区的孢粉学资料,为上海地区进行地层年代划分和对比提供了证据。 相似文献
9.
贵州梵净山九龙池一万年来的植被和气候变化 总被引：4，自引：0，他引：4
九龙池剖面是梵净山顶上的一个洼地剖面,深6.05m,未达基岩。采样112块,孢粉分析鉴定获得孢粉24539粒,有75个科属,以木本花粉为主,其次为蕨类孢子,草本少。根据孢粉组合及~(14)C年龄,该剖面为一万年来的沉积物。其古植被、古气候可分为三个发展时期:(Ⅰ)距今8100—10000年左右为少量落叶阔叶树及较多蕨类组成的疏树蕨类——不很繁茂的落叶阔叶林(林下蕨多)。气候由温凉—稍转温暖。(Ⅱ)距今1300—8100年左右,阔叶林繁盛时期,植被由落叶阔叶树为主的常绿、落叶阔叶混交林——常绿阔叶树为主的常绿、落叶阔叶混交林——落叶阔叶树为主的常绿、落叶阔叶混交林——落叶阔叶林。气候相应由温暖—温暖湿热—温暖—温暖偏凉。(Ⅲ)距今1300—900年左右,以松、栎为主的针阔叶混交林及喜冷湿的莎草较多,气候温暖偏凉湿。 笔者等认为,其气候期的划分(Ⅰ)代表前北方期一北方期,(Ⅱ)代表大西洋期—亚北方期—亚大西洋期(Ⅲ)代表亚大西洋期后的气候。 相似文献
10.
Palynology, texture, mineralogy, geochemistry, and magnetic susceptibility analysis of a 2 m deep sediment core from Padauna Swamp, southeastern Madhya Pradesh infers that between 8600 and 7500 cal yr BP a warm and relatively less-humid climate prevailed with open tree-savannahs dominated by grasses followed by sedges, Artemisia and members of Chenopodiaceae/Amaranthaceae with scanty trees viz., Schrebera, Aegle marmelos and Sterculia urens. This is well supported by lower organic to carbonate carbon ratio, coarser texture having relatively low CIA and magnetic susceptibility values and presence of some primary minerals. Between 7500 and 6250 cal yr BP the tree-savannahs were succeeded by open mixed deciduous forests with the invasion of a few more trees viz., Madhuca indica, Holoptelea, Emblica officinalis, Mitragyna parvifolia and members of Anacardiaceae in response to onset of a warm and humid climate. A considerable rise in organic carbon generated from the degradation of plentiful biomass along with increase in clay content with signs of kaolinite and increase in immobile over mobile elements with slightly higher CIA and magnetic susceptibility values also suggest climatic amelioration. The presence of ruderal plants such as Artemisia, Cannabis sativa and Cheno/Am further infers initiation of human activities in the region. Between 6250 and 2800 cal yr BP, the mixed deciduous forests became more diverse and dense, subduing grasses and other herbaceous elements. Sporadic incursion of Shorea robusta (Sal) in forest floristic was recorded around 5000 cal yr BP. The overall change in the vegetation mosaic reflects that a warm and more-humid climate prevailed in the region, probably on account of invigoration of southwest monsoon. This observation is further corroborated by other proxy data showing a spurt in organic/inorganic carbon ratio, increase in clay content with matured mineralogy, significantly higher CIA and magnetic susceptibility values. Since 2800 cal yr BP onwards, the modern Sal dominated deciduous forests were established indicating continuation of warm and more-humid climate including timely arrival of SW monsoon coinciding with the shedding of Sal seeds as they are viable for a very short period. 相似文献
1