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1.
古近纪早期,地球上发生了古新世-始新世极热气候(PETM)事件,严重影响全球碳循环过程和海陆生态环境系统.依据普通薄片、元素分析、碳同位素、TOC等实验结果.研究了渤海湾盆地济阳断陷湖盆古新世-始新世时期的湖泊环境时空波动变化及其对PETM事件的响应,发现济阳断陷湖盆早期经历了多旋回的演化过程,湖盆中碎屑物质和化学物质的分异作用同时发生,陆地风化作用和化学沉积物质分异指示了极热气候的变化过程;该时期湖水为逐渐咸化的盐湖环境,具有空间的分带性和时间的阶段演化性,湖水咸化是热气候事件发生的直接响应;湖泊的时空波动演化经历了古新世-始新世时期的极热气候(PETM)事件,该事件早期湖泊尚未完全咸化,浮游生物比较繁盛,早期浮游植物对12CO2的吸收,会导致短暂的湖泊古生产力较高,但是随着湖盆逐渐咸化,生物的活动存活较难,主要以旱生植物为主,古生产力降到最低.由于过量的12C吸收沉淀,造成湖泊沉积记录中的δ13C明显负偏,最大可达5×10-3.由此证实全球PETM事件影响了古新世-始新世之交济阳断陷湖盆的时空演化和物质分异过程. 相似文献
2.
古新世—始新世最热事件对地球表层循环的影响及其触发机制 总被引：1，自引：0，他引：1
古新世—始新世最热事件（PETM, Paleocene Eocene Thermal Maximum）是发生在古新世—始新世交界时的一次全球性的气候突变事件。它造成了大洋环流模式的突然倒转和海水盐度、大气湿度的迅速上升。海洋表层生态系统和陆地生态系统生产力迅速上升,许多属种的植物、动物、微生物生活范围向高纬区扩大;大洋底栖微生物发生集群灭绝。现代哺乳动物的主要属种（灵长类、奇蹄类及偶蹄类）产生,哺乳动物演化进程发生重大改变。地球表层碳循环系统发生不同程度的碳同位素负偏移,全球碳循环系统发生大规模搅动。对于PETM的触发机制,主流的观点认为是海底天然气水合物突然释放造成巨量甲烷迅速进入表层系统引发的碳循环系统内部反馈。而对于甲烷释放的原因,又存在着减压释放和热释放两种解释;此外还有科学家用岩浆作用和地外星体撞击来解释PETM的发生。 相似文献
3.
地质历史时期曾发过许多对生命的演化进程造成过重大影响与制约的全球性地质事件,白垩纪—古近纪就是一个重大地质事件频发的时期。随着冈瓦纳大陆在中生代时期的解体,全球海陆格局发生了根本的变化,地球的表层和岩石圈层均发生了重大的改变,由此引发了构造运动空前活跃,发生过诸如大洋缺氧事件(OAE)、大洋富氧事件(CORBs)、白垩纪/古近纪(K/Pg)生物大灭绝事件、古新世—始新世极热(PETM)事件、印度-亚洲板块碰撞、新特提斯洋的演化及最终消亡等一系列的全球性重大地质事件。对这些重大地质事件的研究,有助于加深我们对古海洋、古地理、古环境的认识。尝试追踪和捕捉这些重大地质事件,恢复和重建古地理,其基础是建立精确的年代地层格架。西藏南部保存了中国最为完整的海相白垩纪—古近纪沉积,完整地记录了上述的全球性重大地质事件,通过对札达、岗巴、定日、亚东、江孜、萨嘎和吉隆等地区高分辨率浮游和底栖有孔虫、介形虫、钙质超微化石和放射虫生物地层学研究,可直接约束全球性重大地质事件发生的时间,并为重建新特提斯洋古海洋环境和古地理提供证据。此外,在重大地质环境突变期间生物的演化过程,也可为探明极端环境变化发生时期气候-环境-生物之间的协同演化关系提供证据。本文系统总结了课题组为主的近年来对藏南白垩纪—古近纪海相地层中微体古生物学的研究成果及重要进展,并对未来研究提出展望。 相似文献
4.
《地学前缘》2020,(6)
地质历史时期曾发过许多对生命的演化进程造成过重大影响与制约的全球性地质事件,白垩纪—古近纪就是一个重大地质事件频发的时期。随着冈瓦纳大陆在中生代时期的解体,全球海陆格局发生了根本的变化,地球的表层和岩石圈层均发生了重大的改变,由此引发了构造运动空前活跃,发生过诸如大洋缺氧事件(OAE)、大洋富氧事件(CORBs)、白垩纪/古近纪(K/Pg)生物大灭绝事件、古新世—始新世极热(PETM)事件、印度-亚洲板块碰撞、新特提斯洋的演化及最终消亡等一系列的全球性重大地质事件。对这些重大地质事件的研究,有助于加深我们对古海洋、古地理、古环境的认识。尝试追踪和捕捉这些重大地质事件,恢复和重建古地理,其基础是建立精确的年代地层格架。西藏南部保存了中国最为完整的海相白垩纪—古近纪沉积,完整地记录了上述的全球性重大地质事件,通过对札达、岗巴、定日、亚东、江孜、萨嘎和吉隆等地区高分辨率浮游和底栖有孔虫、介形虫、钙质超微化石和放射虫生物地层学研究,可直接约束全球性重大地质事件发生的时间,并为重建新特提斯洋古海洋环境和古地理提供证据。此外,在重大地质环境突变期间生物的演化过程,也可为探明极端环境变化发生时期气候-环境-生物之间的协同演化关系提供证据。本文系统总结了课题组为主的近年来对藏南白垩纪—古近纪海相地层中微体古生物学的研究成果及重要进展,并对未来研究提出展望。 相似文献
5.
通过对南中国海重力活塞岩芯８ＫＬ的４个浮游有孔虫种和２个底栖有孔虫的δ１８Ｏ和δ１３Ｃ则定，发现浮游和底栖有孔虫种的氧同位素记录可清晰地划分出１８６Ｋａ以来的氧同位素的１-６期。浮游有孔虫的碳同位素记录了氧同位素１／２和５／６期界限处两个明显变轻的事件。反映了由冰期向间冰期过渡时存在着显著的中层水和底层水上涌现象。根据浮游有孔虫种的氧同位素组成判断，各浮游有孔虫种的生存深度由浅至深依次为，Ｇｌｏｂｉｄｅｒｉｎｏｉｄｅｓｒｕｂｅｒ（ｐｉｎｋ），Ｇ·ｒｕｂｅｒ和Ｇ．ｓａｃｃｕｌｉｆｅｒ。氧同位素地层学研究表明，南中国海冰期时的沉积速率和沉积通量要明显大于间冰期。 相似文献
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7.
古近纪气候变化在东海盆地内的化石记录 总被引：1，自引：1，他引：0
古近纪气候演化经历了由"温室气候"向"温凉气候"转变的过程,在此期间发生了三次显著的气候事件,分别为PETM极热事件、Oi-L骤冷事件和Mi-L降温事件。利用东海陆架盆地内孢粉、有孔虫等古生物资料探讨了全球古气候变化背景下东海陆架盆地内古生物差异性变化,并根据特征孢粉组合恢复东海陆架盆地内不同时期古植被以及古气候,在此基础上将东海陆架盆地温度、湿度变化曲线与全球温度变化曲线、海平面变化作对比分析,结果显示东海陆架盆地气候演变与全球气候变化具有一定的耦合关系,并且对渐新世时期东海陆架盆地气候变化的原因进行了初步探讨,认为渐新世时期季风气候的形成导致了东海陆架盆地花港组整体呈现湿润的气候特征。 相似文献
8.
古新世—始新世极热事件（Paleocene—Eocene thermal maximum, PETM）是发生在古新世与始新世界线附近的一次全球快速增温事件。研究显示,PETM期间全球大气CO2浓度增加,温度上升,陆地水循环加强,在陆地和海洋中产生了一系列生物—环境响应。目前,PETM研究主要集中在海相地层中,而针对陆相地层的相关报道并不多见。陆相沉积速率较快,沉积地层厚度大,并且保存有丰富的哺乳动物化石和植物孢粉,也适合开展高分辨率古气候研究。本文对北美、欧洲西部和我国典型陆相盆地的PETM研究成果进行了系统性综述,对比分析结果表明,PETM期间陆相地层中的碳同位素偏移过程可以分为快速负偏、保持低值和缓慢恢复三个阶段。陆地植物和哺乳动物在PETM期间并未经历大规模灭绝,反而通过进化、扩散和局部灭绝适应了快速变化的环境。基于最新的研究方法,包括碳酸盐岩U Pb定年、汞同位素以及团簇同位素,对我国未来的PETM陆相记录研究提出了展望。 相似文献
9.
古新世—始新世极热事件(Paleocene—Eocene thermal maximum, PETM)是发生在古新世与始新世界线附近的一次全球快速增温事件。研究显示,PETM期间全球大气CO2浓度增加,温度上升,陆地水循环加强,在陆地和海洋中产生了一系列生物—环境响应。目前,PETM研究主要集中在海相地层中,而针对陆相地层的相关报道并不多见。陆相沉积速率较快,沉积地层厚度大,并且保存有丰富的哺乳动物化石和植物孢粉,也适合开展高分辨率古气候研究。本文对北美、欧洲西部和我国典型陆相盆地的PETM研究成果进行了系统性综述,对比分析结果表明,PETM期间陆相地层中的碳同位素偏移过程可以分为快速负偏、保持低值和缓慢恢复三个阶段。陆地植物和哺乳动物在PETM期间并未经历大规模灭绝,反而通过进化、扩散和局部灭绝适应了快速变化的环境。基于最新的研究方法,包括碳酸盐岩U-Pb定年、汞同位素以及团簇同位素,对我国未来的PETM陆相记录研究提出了展望。 相似文献
10.
古近纪古新世—始新世极热事件和始新世后期变冷的古气候事件是目前沉积学和古气候学研究的热点, 但相关研究在陆相地层中较少涉及。前人对抚顺盆地始新世一系列极热事件进行了识别和成因研究, 但针对始新世后期开始变冷的古气候波动状况尚未进行系统分析。本文采用了古气候参数磁化率和色度对抚顺盆地始新世西露天组(晚始新世)古气候的波动和演化特征进行研究。通过对高精度磁化率和色度数据进行聚类分析和垂向演化规律对比发现, 西露天组沉积记录具有高的频率磁化率(12.58%~39.63%)、中高色度a*值(5.6%左右)和中高色度b*值(9.1%左右), 且这些数值均与古气温具有很好的对应性, 鉴于此, 这两种参数可以作为始新世陆相古气候演化研究的有效手段。抚顺盆地西露天组自底部到顶部, 频率磁化率呈由高值到低值缓慢下降的趋势, 色度a*值和b*值总体呈现先增加后减少的趋势, 这些均显示了抚顺盆地始新世整体温室气候背景下的降温过程。本次对晚始新世古气候变化趋势研究的认识, 联合前人在早始新世古气候演化的研究成果, 可以共同为东亚地区完整的始新世古气候演化研究提供可靠素材。 相似文献
11.
Lamia ZILI 《《地质学报》英文版》2013,87(6):1533-1539
A new section at Jebel Gorraa,in northern Tunisia,contains the Paleocene-Eocene transition interval.Sample analysis of the section delivers abundant and diverse microfauna of planktonic and benthic foraminifera.Biostratigraphically,the Acarinina sibaiyaensis index-species is identified for the first time in this region,which allows us to specify the location of the Paleocene-Eocene boundary as well as the first E1 biozone of the lower Eocene.Samples from this biozone contain calcitic tests poorly preserved with an enrichment of iron oxide signifying a period of upheaval in local marine environments linked to the global warming of the Paleocene-Eocene Thermal Maximum （PETM）,the marker for the P/E boundary. 相似文献
12.
D. M. Ol’shanetsky 《Russian Journal of Pacific Geology》2018,12(2):93-118
Based on the stratigraphic distribution of benthic foraminifera in the lower bathyal–abyssal sediments uncovered by boreholes drilled under the framework of the Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) in the Northern and Southern Pacific, the Lower Paleogene biostratigraphic zonal scale based on deep-water benthic foraminifera is proposed. The proposed scale includes eight subdivisions: six zones and two subzones. The boundaries of the zonal subdivisions are determined by biotic events (appearance or disappearance (extinction)) of stratigraphically important taxa and are correlated to the zonal scales based on planktonic foraminifera and calcareous nanoplankton. Most of these events are considered to be subglobal. 相似文献
13.
随着深海钻探计划(DSDP)和大洋钻探计划(ODP)的开展,在古海洋学领域取得了许多重大发现。古近纪古新世与始新世(P/E)界线间的地质事件的发现便是其重要成果之一。西藏南部岗巴地区发育有良好的海相界线地层。对生物群、碳、氧、锶稳定同位素以及磁化率的研究显示,全球界线事件在西藏南部岗巴地区具有明显的影响。古新统宗浦组顶部底栖有孔虫动物群阶段性绝灭,总灭绝率为69%。始新统遮普惹组底部有孔虫逐渐复苏,除12种为古新世的残存类型外,始新世生物组合全为新的属种,并呈现三个复苏阶段。碳稳定同位素表现为三期负向偏移,在界线处出现-4‰的异常。这一异常与全球碳稳定同位素事件表现一致。锶同位素在界线位置没有明显的变化,而明显的峰值出现在界线之上,并与全球53Ma出现的锶同位素变化相对应。磁化率在界线之上2m处出现一个很明显的波动,与第3期碳同位素异常吻合。所有研究结果表明,西藏南部(特提斯-喜马拉雅低纬度浅海环境)在古新世与始新世界线时期出现明显的气候变化,说明全球深海温度增高在浅海环境具有相同表现,只是影响时间较长。 相似文献
14.
The early Paleogene experienced the most pronounced long-term warming trend of the Cenozoic, superimposed by transient warming events such as the Paleocene–Eocene Thermal Maximum (PETM). The consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored. Today, modern carbonate platforms, especially coral reefs are highly sensitive to environmental and climatic change, which raises the question how (sub)tropical reef systems of the early Paleogene reacted to gradual and sudden global warming, eutrophication of shelf areas, enhanced CO2 levels in an ocean with low Mg/Ca ratios. The answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising CO2 levels.Here we present a synthesis of Tethyan carbonate platform evolution in the early Paleogene (~ 59–55 Ma) concentrating on coral reefs and larger foraminifera, two important organism groups during this time interval. We discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early Paleogene. Detailed analyses of two carbonate platform areas at low (Egypt) and middle (Spain) paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late Paleocene to early Eocene Tethys: Stage I, late Paleocene coralgal-dominated platforms at low to middle paleolatitudes; stage II, a transitional latest Paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera-dominated (Miscellanea, Ranikothalia, Assilina) platforms at low paleolatitudes; and stage III, early Eocene larger foraminifera-dominated (Alveolina, Orbitolites, Nummulites) platforms at low to middle paleolatitudes. The onset of the latter prominent larger foraminifera-dominated platform correlates with the Paleocene/Eocene Thermal Maximum.The causes for the change from coral-dominated platforms to larger foraminifera-dominated platforms are multilayered. The decline of coralgal reefs in low latitudes during platform stage II is related to overall warming, leading to sea-surface temperatures in the tropics beyond the maximum temperature range of corals. The overall low occurrence of coral reefs in the Paleogene might be related to the presence of a calcite sea. At the same time larger foraminifera started to flourish after their near extinction at the Cretaceous/Paleogene boundary. The demise of coralgal reefs at all studied paleolatitudes in platform stage III can be founded on the effects of the PETM, resulting in short-term warming, eutrophic conditions on the shelves and acidification of the oceans, hampering the growth of aragonitic corals, while calcitic larger foraminifera flourished. In the absence of other successful carbonate-producing organisms, larger foraminifera were able to take over the role as the dominant carbonate platform inhabitant, leading to a stepwise Tethyan platform stage evolution around the Paleocene/Eocene boundary. This szenario might be also effective for threatened coral reef sites. 相似文献
15.
Hassan A. Soliman Nageh A. Obaidalla Amr A. Metwally Azza A. Mohamed 《Arabian Journal of Geosciences》2018,11(14):394
Benthic foraminiferal fauna are analyzed quantitatively and qualitatively at three stratigraphic sections in Eastern Desert of Egypt (Serai, Duwi, and Um El Huetat). These sections embrace the Paleocene–Eocene Thermal Maximum (PETM) interval which is represented by the occurrence of five distinctive beds. These beds constitute the Dababiya Quarry Member at the lower part of Esna Formation. The occurrence of them indicates an expanded and relatively continuous record across the P/E boundary. The organic-rich clay layer (bed no. 1 of the Dababiya Quarry Member) marks the start of the PETM event. This bed is characterized by the extinction of all benthic foraminiferal fauna except for the occurrence of rare agglutinated foraminiferal species. The presence of these species indicates an oceanic anoxic event at the sea floor. High concentration of phosphatic contents including fish remains occurred in the middle part of the PETM (bed nos. 2 and 3 of the Dababiya Quarry Member) with the continuous absence of benthic foraminiferal fauna except for few specimens at the top of bed 3. Bed nos. 4 and 5 of the Dababiya Quarry Member represent the upper part of the PETM and the initial stage of sea floor recovery. Low diversity and abundance of benthic foraminiferal taxa occurred within these beds, represented by Valvulineria scrobiculata, Lenticulina midwayensis, Loxostomoides appliane, and Siphogenerinoides eleganta. This phenomenon continues upward during the post-PETM event. The Paleocene velasco-type benthic foraminifera Angulogavelinella avnimelechi and Coryphostoma midwayensis species are extinct within the advent of the PETM event. The benthic foraminiferal assemblages at the studied sections are dominated by midway-type fauna with little representative of velasco-type fauna. The velasco-type species are represented with high abundance at Serai section and with low densities at Um El Huetat section, while at Duwi section, they rarely occurred. This suggests outer neritic-upper bathyal (150–400 m) setting at Serai section and mostly middle-outer neritic (50–150 m) setting at Um El Huetat and Duwi sections. 相似文献
16.
The Paleocene/Eocene boundary intervals were studied in three outcrops along the Nile Valley: Gabal Taramsa, Gabal Qreiya, and Gabal Nag El Quda in Qena and Esna regions. The planktonic and benthic foraminifera have been examined. The qualitative study of planktonic foraminifera distinguishes eight planktonic biozones from (P4 and P5) Paleocene age to (E1, E2, E3, E4, E5, and E6) Early Eocene age. The analysis of quantitative distribution patterns of benthic foraminifera allows the reconstruction of the paleoenvironmental settings in the studied area. The disappearance or scarce appearance of deeper-water benthic foraminifera (Angulogavelinella avnimelechi and Gavelinella rubiginosus) and increasing dominance of shallow-marine taxa (Buliminides, Loxostomoides applinae) indicate deposition in shallow water environments. The benthic foraminiferal assemblages which dominated by Loxostomoides applinae, Buliminids, and Lenticulina indicate Dysoxic conditions and maximum food levels. The species of mid-way type fauna dominate the assemblages of the studied area; the species of Velasco-type fauna are very rare. 相似文献