共查询到18条相似文献，搜索用时 640 毫秒
1.
湘鄂西部地区晚奥陶世三叶虫相和古地理演化 总被引：10，自引：0，他引：10
对湘鄂西地区 8个晚奥陶世剖面的 3个时段 (Caradoc中期 ,晚期及 Ashgill早期 )地层作了详细采集 ,获得了丰富的三叶虫材料 ,根据动物群的组成、分异度和各组成分子的相对丰度 ,识别出外陆棚—棚外深水区的 9种三叶虫相 ,它们在时空分布上具有逐渐过渡更替的特征。根据水中浮游类型三叶虫 (圆尾虫类 )的分异度、相对丰度以及与它们共生的底栖三叶虫生态特征 ,对各种三叶虫相所指示的水体深度作了推测。三叶虫相研究表明 ,区内Caradoc中期处于海侵高峰 ,古地理样式显示了以拉张为主的区域构造背景 ;Caradoc晚期开始发生持续海退 ,同时扬子陆块南缘受到构造挤压 ,广大外陆棚区地形变得起伏不平。晚奥陶世古地理变迁证明华夏和扬子陆块的会聚事件始于 Caradoc晚期 相似文献
2.
华南上扬子区早-中奥陶世疑源类古环境意义 总被引：1，自引：2，他引：1
对上扬子区 7个剖面早—中奥陶世疑源类研究表明 ,这些疑源类组合在分异度及属种组成上呈现有规律的变化 ,这种变化是上扬子区古环境变化的反映。在上扬子区西部 ,近岸碎屑岩相沉积的滇东红石崖组所产疑源类组合分异度低 ,为个体较小、壳饰较简单的分子 ;上扬子区中部 ,以黔北湄潭组为代表的浅海相碎屑岩和灰岩沉积中 ,疑源类分异度较高 ,并出现许多个体较大、壳饰较复杂的分子 ;而在上扬子区东部鄂西宜昌大湾组陆棚相灰岩与泥岩中 ,疑源类分异度继续增高 ,其中个体大、具粗大、长而复杂突起的分子占优势。 相似文献
3.
下扬子地区中二叠世上升流相区古生态学研究 总被引：4，自引：1，他引：3
首次对下扬子地区中二叠世上升流相区古生态特征进行了研究。将栖霞组划分为5个沉积期,并划分了栖霞组各沉积期和茅口期的生物群落,其中本部灰岩段和顶部灰岩段沉积期群落分异较为明显,并阐述了各群落的组成、结构和生态环境。根据群落的组合特征和沉积学特征,在研究区识别出两种生物相类型,即陆棚缓坡底栖型生物相和陆棚盆地浮游型生物相,并论述了生物相与上升流强度之间的关系。最后,分析了上升流对生物古生态特征的控制作用,认为,上升流的发育强度和生物群落的丰度成正相关,而与分异度多成反相关。 相似文献
4.
扬子地块北缘与秦岭接壤,早古生代经历了上扬子克拉通盆地(∈-O2)和隆后盆地(O3-S)两个阶段。区内发育上奥陶统观音桥组或南郑组地层,为研究赫南特期的岩相古地理,探讨赫南特期冰川事件的沉积响应奠定了坚实的基础。根据沉积特征,结合古生物组合,扬子地块北缘观音桥组可划分为滨岸相和陆棚相。按照岩性等,陆棚相可进一步划分为陆缘碎屑陆棚相、混积陆棚相。滨岸相主要由石英砂岩、钙质砂岩和含砾砂岩组成,发育少量生物,以腕足为主;而在陆棚相中,则是以含粉砂泥岩、生屑灰岩、泥灰岩夹钙质泥岩和含钙泥岩为主,富含生物,以三叶虫(Dalmanitina)、腕足以及标志性冷水、浅水Hirnantia动物群为主。在沉积相详细研究的基础上,分析了该时期的岩相古地理面貌及其空间分布。在北部和西部,继续早期的格局,持续存在汉南隆起,围绕隆起分布的是滨岸相;往南至大两会-桥亭一线,为陆缘碎屑浅海陆棚,大两会-桥亭一线往南区域分布为混积陆棚。由于在研究区,无论在滨岸地带还是浅海地区,均发育赫南特贝化石,说明在赫南特期,由于受南冈瓦纳冰川事件的影响,冰水侵进扬子北缘全区。这次冰川事件导致海平面下降,致使扬子北缘水体变浅,早期的深水陆棚变为浅水陆棚,生物也由浮游相笔石迅速变为壳相赫南特贝,早期隆起范围进一步扩大,并出现地层的缺失。 相似文献
5.
华南地区奥陶纪头足类生物相及其分区 总被引：2，自引：0，他引：2
在研究华南地区奥陶纪头足类生态特征基础上，根据头足类的生态类型及其保存条件等特征，识别出18个头足类生物相，即开阔台地[WT5”BX]Proterocameroceras生物相，局限台地Pseudoectenolites-Xiadongoceras生物相，开阔台地Retroclitendoceras-Pararetrocli tendoceras生物相，开阔台地Pronajaceras-Mamagouceras生物相，陆棚斜坡—盆地Cyclostomiceras-Bactroceras生物相，开阔台地 Cameroceras-Cyrtovaginoceras生物相，开阔台地 Coreanoceras-Manchuroceras生物相，陆棚斜坡—盆地Kaipingoceras-Kyminoceras生物相，内陆棚Bathmoceras-Protocycloceras生物相，中部陆棚Dideroceras-Ancistroceras生物相，深水陆棚 Lituites-Cyclolituites 生物相，滞流盆地Lituites-Trilacinoceras生物相，深水盆地Paraendoceras-Sactorthoceras，深水陆棚Sinoceras-Michelinoceras-Disoceras生物相，深水陆棚Beloitoceras-Jiangshanoceras生物相，深水陆棚—盆地Eurasiaticoceras生物相，浅海陆棚—斜坡Jiangxiceras-Yushanoceras生物相，深水盆地Michelinoceras[WT5”BZ]生物相，并阐述各生物相的组成、生态特征及其生态环境。根据头足类生物相在时间和空间上的组合规律，划分出3个头足类生物相区，即扬子生物相区、黔东—湘西生物相区（过渡型生物相区）和湘中—浙西生物相区，并讨论了各生物相区在不同时期内头足类生态类型和生物相分异特征、海平面升降、环境演变特征以及其与油气的关系。认为在低海平面或海平面下降阶段中生物相分异明显，而在高海平面阶段中则分异较小。 相似文献
6.
西秦岭的南带在加里东构造阶段处于被动大陆边缘。自中志留世至早泥盆世相继沉积了碎屑潮坪、碎屑陆棚、深水复理石及灰泥潮坪等沉积相。各相中保存了相应的遗迹相:Plaolitesn遗迹相产于若尔盖古陆北侧的碎屑潮坪环境:Cruziana遗迹相,保存在下临滨的石英砂岩与黑色泥质岩的交界面中;Nereites遗迹相,保存于多级韵律互层的复理石中,其丰度及分异度极高。以牧食迹为主,耕食迹也很丰富,属浊积外扇类型,Glossifungites遗迹相,保存于下泥盆统灰泥潮坪相。以滤食生物的居住潸穴为主。除Planolites遗迹组合外,其余的遗迹相均可与Seilacher(1967,1968)建立的遗迹相对比。这些遗迹相的发现,对研究西秦岭南带中古生代的沉积环境及构造运动有重要意义。 相似文献
7.
西秦岭的南带在加里东构造阶段处于被动大陆边缘。自中志留世至早泥盆世相继沉积了碎屑潮坪、碎届陆棚、深水复理石及灰泥潮坪等沉积相。各相中保存了相应的遗迹相;Plaolitesn遗迹相产于若尔盖古陆北侧的碎屑潮坪环境;Cruziana遗迹相,保存在下临滨的石英砂岩与黑色泥质岩的交界面中;Nereites遗迹相,保存于多级韵律互层的复理石中,其丰度及分异度极高。以牧食迹为主,耕食迹也很丰富,属浊积外扇类型;Glossifungites遗迹相,保存于下泥盆统灰泥潮坪相。以滤食生物的居住潸穴为主。除Planolites遗迹组合外,其余的遗迹相均可与Seilacher(1967,1968)建立的遗迹相对比。这些遗迹相的发现,对研究西秦岭南带中古生代的沉积环境及构造运动有重要意义。 相似文献
8.
湘鄂西奥陶纪Tremadocian期三叶虫相 总被引：5，自引：0，他引：5
分析了湘鄂西地区 5个剖面的奥陶纪 Tremadocian期三叶虫动物群 ,识别出 6个三叶虫相 ,即台地的 Asa-phellus- Dactylocephalus相、Dikelokephalinid相、Tungtzuella- Asaphopsis相、Psilocephalina 相 ,陆棚上斜坡的Metayuepingia- shumardiid相 ,陆棚下斜坡的 Olenid相 ;恢复了该地区 C.angulatus期、P.deltifer早—中期和 P.deltifer末期— Serratognatus期三个时段的古地理面貌 ,揭示了区内发生于 G.quadraplicatus期、P.deltifer末期和 Serratognatus中—后期的三次海退事件和发生于 P.deltifer早—中期和 Serratognatus初期的两次海侵事件 相似文献
9.
凯里化石库：一个新的中寒武世布尔吉斯页岩型化石库 总被引：6，自引：1，他引：6
凯里化石库拥有１０多个门类、７０多个属。动物化石５８属，仅次于Ｂｕｒｇｅｓｓ及澄江化石库。同Ｓｐｅｎｃｅ化石库一样，非三叶虫节肢动物及软躯体化石比较少，三叶虫多，有别于Ｂｕｒｇｅｓｓ、澄江、ＳｉｒｉｕｓＰａｓｓｅｔ化石库等另一类型的布尔吉斯页岩型化石库。该化石库时代早于Ｓｐｅｎｃｅ、Ｂｕｒｇｅｓｓ化石库，是布尔吉斯页岩型化石库时代序列中重要的一环。形成于中寒武世赤道附近稳定的扬子碳酸盐台地东缘外迅速下沉的陆棚水体较深的环境，与Ｓｐｅｎｃｅ化石库的大地构造位置、沉积环境及埋藏模式等均很相似，证实中寒武世Ｂｕｒｇｅｓｓ页岩型化石库分布于稳定的克拉通周缘陆棚海的规律。凯里化石库的发现还增添了寒武纪古生物多样化的新信息。 相似文献
10.
秦岭褶皱带位于华北板块和扬子板块结合部位，其在河南省内的部分多划为东秦岭。东秦岭以商南-镇平缝合带分为东秦岭北部和东秦岭南部。东秦岭古生代生物古地理演变可以划分为6个阶段。在寒武纪至中奥陶世早期，东秦岭北部二郎坪海槽的寒武纪放射虫和早奥陶世牙形石与东秦岭南部淅川陆棚北部的寒武纪三叶虫、早奥陶世牙形石和头足类属华南生物省，而淅川陆棚南部的寒武纪三叶虫和早奥陶世牙形石属于华南生物省，兼有华北生物省分子。在中奥陶世晚期至奥陶纪末，二郎坪海槽的腹足类、头足类和珊瑚与淅川陆棚的牙形石、珊瑚、腕足类、头足类和三叶虫均属华北生物省。在早志留世，二郎坪海槽的珊瑚与淅川陆棚的笔石属华南生物省。在中志留世至早泥盆世，东秦岭未发现古生物化石，很可能为陆地，并与华北陆块联为一体。在中泥盆世至早石炭世，东秦岭北部柿树园海槽与东秦岭南部南湾海槽的孢子及淅川陆棚的晚泥盆世珊瑚、腕足类和古植物及早石炭世蜓属华南生物省。晚石炭世至二叠纪末，柿树园海槽的孢子见于华北生物省，东秦岭南部缺乏海相沉积。总之，在古生代，东秦岭经历了由华南生物省→华北生物省→华南生物省→华北陆→华南生物省→华北生物省6个阶段，组成3个演变旋回。东秦岭北部和南部生物古地理具有明显的演变方向的统一性和演变时间的相似性。 相似文献
11.
This study examines benthic foraminifera (>63 μm) both qualitatively and quantitatively, from 19 closely spaced surficial sediment samples covering 30 to 200 m water depths across the shelf and upper continental slope off north Kerala (SW India). A total of 59 species are recorded. The major constituents of benthic foraminiferal assemblages in the study area are fursenkoinids, bolivinids, nonionids, rotaliids, elphidiids, buliminids, miliolids, gavilinellids, amphestiginids, bagginids, vaginulinids, uvigerinids and various agglutinated taxa. Cluster analysis using Bray Curtis similarity index defines four sample groups, each typified by a characteristic assemblage representing a biofacies. The major benthic foraminiferal biofacies identified are: Biofacies I, Fursenkoina-Nonion-Ammonia beccarii s.l. (30–40 m); Biofacies II, Fursenkoina-Nonion (40–55 m); Biofacies III, Bolivina robusta-Hanzawaia-Cancris-Amphistegina and miliolids (55–115 m) and Biofacies IV, Bolivina persiensis-Uvigerina-Bulimina-Fursenkoina and agglutinants (115–200 m). Relict foraminifera, most commonly represented by shallow-water benthic taxa are concentrated on the outer shelf. The relict assemblage appears to be a product of late Pleistocene low sea level. The foraminiferal biofacies have a good correspondence with the bathymetrically distributed three major lithofacies across the shelf and the upper continental slope. We studied the distribution pattern of individual taxa constituting the biofacies. The study demonstrates a relationship between the pattern of distribution of major benthic fauna and the sediment-size and organic carbon content across the inner shelf to upper slope. Additionally, certain taxa appear to be sensitive to various hydrographic parameters, such as, Bulimina marginata to temperature and Fursenkoina complanata and Uvigerina ex gr. U. semiornata to dissolved oxygen level. 相似文献
12.
Documentation of non- or weakly biomineralizing animals that lived during the Furongian is essential for a comprehensive understanding of the diversification dynamics of metazoans during the early Palaeozoic. However, the fossil record of ‘soft’-bodied metazoans is particularly scarce for this critical time interval, consisting of rare fossils found at a dozen or so localities worldwide. Here we report new occurrences of exceptional preservation in Furongian (Jiangshanian) strata of the McKay Group near Cranbrook, British Columbia, Canada. This locality had already yielded trilobites with phosphatised guts, with all specimens representing the same species and occurring within a 10-m-thick interval. Two stratigraphically higher horizons with soft-tissue preservation are reported herein; one has yielded a ctenophore and an aglaspidid arthropod, the other a trilobite with a phosphatised gut belonging to a different species than the previously described specimens. The ctenophore represents the first Furongian record of the phylum and the first reported occurrence of Burgess Shale-type preservation in the upper Cambrian of Laurentia. The aglaspidid belongs to a new species of Glypharthrus, and is atypical in having twelve trunk tergites and an anteriorly narrow ‘tailspine’. These features suggest that the tailspine of aglaspidids evolved from the fusion of a twelfth trunk segment with the telson. They also confirm the vicissicaudatan affinities of these extinct arthropods. Compositional analyses suggest that aglaspidid cuticle was essentially organic with a thin biomineralised (apatitic) outer layer. The trilobite reveals previously unknown gut features, such as medial fusion of digestive glands, possibly related to enhanced capabilities for digestion, storage, or the assimilation of food. The new fossils demonstrate that conditions conducive to soft-tissue preservation repeatedly developed in the outer shelf environment represented by the Furongian strata near Cranbrook. Future exploration of the c. 600-m-thick, mudstone-dominated upper part of the section may result in more abundant discoveries of exceptional fossils. 相似文献
13.
宜昌地区下奥陶统主要为一套台地相碳酸盐沉积,间夹页岩,其中的特征沉积为发育有较多的生物礁。造礁生物主要有海绵类、瓶筐石类、有柄棘皮类、苔藓虫及蓝细菌和Pulchrilamina等。在下奥陶统含礁层系中识别出四种生物相：(1)壳类生物相：发育有Tritoechia-Pelmatozans群落和Tritoechia-Pomatotrema群落;(2)礁生物相：包括Batostoma群落、Calathium--Archaeoscyphia群落、Pelmatozoans--Batostoma群落、Archeoscyphia群落和Calathium--Cyanobacteria群落;(3)静水生物相：发育有Acanthograptus--Dendrogptus群落和Yichangopora群落;(4)异地生物相：产有异地埋藏群,即Nanorthis--Psilocephlina埋藏群。含礁层系存在四个海平面变化旋回,生物礁的发育明显受海平面的升降速率与容纳空间增长速率的控制。生物礁多形成于高海平面时期。由于本区的海平面在上升过程中存在多个次一级旋回,致使生物礁具有数量多、分布广以及厚度薄和规模小等特点。造礁群落存在着演替和取代两种形式,前者有利于生物礁的发育,后者则表现为礁体的衰亡。 相似文献
14.
Blanca Martínez‐García Arantxa Bodego Jone Mendicoa Ana Pascual Julio Rodríguez‐Lázaro 《Boreas: An International Journal of Quaternary Research》2014,43(4):973-988
Late Quaternary (MIS 3 to Recent) oceanographic evolution of the Basque shelf has been analysed for the first time based on the sedimentological analysis of three cores obtained from the middle and outer shelves. The cores are located in two interfluves separated by the San Sebastian canyon. The variability of the percentage of the planktonic foraminifera species Neogloboquadrina pachyderma sin. and of δ18Obull allowed us to identify the influence of colder and warmer waters in the Basque shelf during the late Quaternary. From ～56 cal. ka BP to the end of the Last Glacial Maximum (19 cal. ka BP) the sedimentary record shows a decreasing trend in the mean grain size that correlates with the eustatic sea‐level fall. The last Deglaciation (19–11.5 cal. ka BP) is characterized by a sea‐level rise that produced an important hiatus in the western outer shelf. During the Holocene, the middle and outer shelves present different behaviours. From 11.5 to 6.7 cal. ka BP, in the outer shelf the sea‐level rise that started during the Deglaciation produced a hiatus, whereas in the middle shelf the sedimentary succession records the presence of warm to temperate waters. Between 6.7–4.9 cal. ka BP, the entrance of cold surface water‐masses that only affected the middle shelf has been identified, and temperate to warm waters occurred in the outer shelf. The cold surface water‐masses retreated during 4.9–4.3 cal. ka BP in the middle shelf. Finally, from 4.3 cal. ka BP to Recent, the middle shelf registers a hiatus due to sea‐level stabilization after a generalized transgression, synchronous to a decrease in the energy of the water‐masses in the outer shelf. In conclusion, the environmental changes detected in the Basque shelf are attributed to both regional and eustatic sea‐level changes. 相似文献
15.
Quaternary seismic stratigraphy and paleoenvironments on the continental shelf of the East China Sea
《Journal of Asian Earth Sciences》2000,18(4):441-452
Paleoenvironments and stratigraphy have been interpreted from 4380 km of seismic profiling collected during a geological and geophysical cruise on the continental shelf of the East China Sea (ECS) undertaken in 1996. The geophysical data are correlated with a borehole situated on the outer shelf obtained by Shanghai Marine Geology Bureau, indicating that six seismic units have been preserved since oxygen-isotope stage 6, including four regressive–transgressive cycles. Seismic units U2, U3+U4+U5, U6, and U7 are interpreted to correspond respectively to oxygen-isotope stages 1, 3, 5, and 6, implying that sediment partitioning and sequence architecture in the ECS have been controlled by glacio-eustasy and global climate changes. Alternating continental and marine strata corresponding to glaciation and interglaciation are well preserved on the outer shelf of the ECS. Most of the cold environment strata, which formed on the outer shelf during oxygen-isotope stages 2 and 4, are too thin to be recognized on SIG 600J because of resolution, but corresponding erosion surfaces exist. Seismic unit U7 is widespread over the shelf, extending to the continental edge and showing little variation in thickness, as the regression was pronounced and lasted a long time. Thus, U7 can be used as a marker layer for correlation of Quaternary strata on the shelf of the ECS. Post-glacial transgression is obvious in the ECS. Marine strata with varied thickness were developed in the shallow sea of the inner shelf, thinning toward the outer shelf. The continental shelf of the ECS has been influenced by Pacific tide-wave systems for a long time, forming tidal sand-ridge sequences, developed during transgressions, corresponding to oxygen-isotope stages 7 (or 9), 5, 3 and 1. 相似文献
16.
丁旋 《吉林大学学报(地球科学版)》1997,(3)
吉林南部晚寒武世凤山期地层出露良好，三叶虫化石丰富，是进行化石群落古生态研究的理想地区。通过埋藏学分析、化石形态功能分析、围岩沉积学研究，在本区建立了六个底栖三叶虫化石群落，自下而上为Ｐｔｙｃｈａｓｐｉｓ－Ｔｓｉｎａｎｉａ群落，Ｑｕａｄｒａｔｉｃｅｐｈａｌｕｓ群落，Ｃｈａｎｇｉａ群落，Ｃａｌｖｉｎｅｌａ群落，Ｍｉｃｔｏｓａｕｋｉａ群落，Ｒｉｃｈａｒｄｓｏｎｅｌａ群落，结合化石群落及其赋存岩性特征，分析本区凤山期沉积环境由前滨－近滨相带渐变为浅海陆棚相带，海水逐渐加深。 相似文献
17.
寒武纪三叶虫生物地理区的一些问题 总被引：1，自引：0，他引：1
文内叙述寒武纪三叶虫分类、分布和分区。世界上有两个寒武纪生物地理区,一个是北区,另一个是南区。斜坡带的球接子类及少数多节类是世界性分布的,仅能视作任何一区内的生态小区。两区的分界在北非的北部、土耳其的南部,再向东连接天山的北部边缘及蒙古的南部边缘。从南欧寒武纪三叶虫的情况看,是海水深度频繁变化的结果。中国任何一个地区,既不属东冈瓦纳,也不属西冈瓦纳。 相似文献
18.
The foraminiferal fauna from two holes near the coastal section of marls and limestones at Torquay is dominated by inner to mid‐shelf benthic forms, especially the cibicidids, discorbids and miliolids. Planktonic species are rare and rarely age‐diagnostic. A cluster analysis of the species occurrences and relative abundances identified four assemblages, A to D up‐section. These assemblages also closely correspond to lithological changes characterising lithostratigraphic units: Angahook Formation (assemblage A), lower and upper Jan Juc Formation (B, C) and Puebla Clay (D). Biofacies trends based on the relative abundances of inner and outer neritic taxa led to the recognition of third‐order sequences and boundaries equivalent to TB1.1 to TB1.4, confirming a previous identification on sedimentological grounds. They demonstrate that foraminiferal assemblages were directly influenced by third‐order sea‐level fluctuations and can be used to predict third‐order sequences. The long‐uncertain regional Oligocene‐Miocene boundary is placed at the Jan Juc Formation—Puebla Clay contact, across which there was a major faunal change. Several benthic forms disappeared, at least temporarily: Cibicidoides perforatus, Amphistegina lessonii and Pararotalia mackayi. The typical Miocene planktonic taxa Globoquadrina dehiscens and Globoturborotalita brazieri made their first appearance. These events were associated with an increase in inner neritic benthos signalling a low sea‐level, consistent with the contemporaneous global pattern. 相似文献