【作者】 贾志海；

【导师】 洪天求；

【作者基本信息】 合肥工业大学 ， 矿物、岩石、矿床学， 2004， 博士

【摘要】 淮南地区新元古代九里桥组主要由泥质、砂质灰岩和白云质灰岩构成，厚度40—70m。该组地层出露完整、沉积类型多样，含有丰富的叠层石礁体、宏体藻类和疑源类化石，并有宏体蠕虫状化石发现，是研究地球早期生命演化、生物与环境相互关系的理想对象。 本研究通过对九里桥组事件沉积、露头层序地层、古生物、叠层石礁体和沉积地球化学等的研究，深入探讨该组沉积期环境的变化及其生物学响应特征，为丰富新元古代古生物学、地球早期生命探索、沉积学和环境科学理论提供新的证据和信息。 根据九里桥组的岩性特征、事件沉积特征、古生物化石的产出特征以及不同露头的对比等，将该组划分为下部含臼齿脉体泥质、砂质灰岩段(厚13—18m)、中部叠层石灰岩段(厚19—62m)和上部含宏体化石砂质灰岩段(厚7—10m)三部分，为该组的其它相关研究奠定了基础。 不同沉积类型的产出特征表明，该组沉积期经历了早期较强的地震活动、中期频繁发生的海洋风暴活动和最大海泛事件、晚期的环境突变事件和海平面下降等。该组沉积早期，强烈的地震活动对造叠层石生物的生长发育具有毁灭性破坏作用。风暴沉积类型的变化特征表明，该组沉积期风暴活动的发展过程经历了沉积早期的风暴偶发期、沉积中期的风暴频发期、减弱期和沉积晚期的风暴平静期四个阶段，在剖面上可划分出5个特征明显的风暴沉积旋回。风暴活动由盛到衰的过程与该组叠层石礁体由小变大、微体浮游生物和宏体化石记录由少增多的过程相对应，这种现象表明频繁发生的风暴活动对这一时期区域性生物的发展具有较为明显的负面影响，但对造叠层石生物的影响远比对其它类型的宏体和微体生物的影响要弱。 采用浸解法，辅助以切片的分析方法，首次从该组中上段碳酸盐岩样品中收集发现了数量众多的疑源类化石，包括Acanthomorphitae(棘刺亚类)、Herkomorphitae(网面亚类)、Pteromorphitae(翼环亚类)、Nematomorphitae(线形亚类)、Sphaeromorphitae(球形亚类)和多细胞植物碎片等在内，共17个形态属、15个种和13个未定种。这些疑源类化石具有青白口纪—震旦纪过渡时期的特征，生物地层意义突出。对比研究表明，该组沉积期微体浮游生物生长发育非常繁盛，反映了微体浮游生物发展新阶段的到来。 宏体古生物化石的埋藏、分布状况、叠层石礁体的产出特征、疑源类化石的分布特征表明，大量的宏体生物、微体浮游生物和造叠层石生物共同组成了该组沉积时期较为复杂的生物群落。不同类型的生物之间存在较为明显的生存竞争现象，并可能导致了食物链的中断，从而在九里桥组上段出现了含宏体生物化石层与含疑源类化石层间隔分布的特征。 该组自下而上，叠层石单体形态的变化趋势为：块茎状、破碎且具分叉的短柱状——完整且不具分叉的长柱状——基本完整的短柱状、块茎状；叠层石礁体的变化趋势为：透镜状、小型丘状——大型丘状——透镜状。根据这些特征将该组沉积期叠层石礁体划分为风暴环境型礁体、海进环境型礁体和海退环境型礁体三种类型，区分出8个叠层石造礁旋回，指示了造叠层石生物对不同环境的适应过程。风暴活动对造叠层石生物的造礁活动具有破坏和促进的双重影响作用，海进过程对造叠层石生物的造礁活动较为有利，但海水的突然加深则对其具有较大的影响并终止其造礁活动，海退过程对造叠层石生物的造礁活动总体上较为不利。 九里桥组碳酸盐岩酸不溶物、元素含量变化特征表明，该组沉积期淮南地区处于浅海环境，并经历了海水由浅—深—浅的变化过程。进一步分析表明，宏体生物比较适合在陆源碎屑供给充足的较浅水域生存繁衍，造叠层石生物能够在潮汐带深度不同的水域生存繁衍，其繁盛的生长活动对非碳酸盐沉积物具有明显的排斥作用，并对Mg、Sr、Ba、Mn、Ti等元素在沉积物中的富积具有波动性影响。 C、O同位素分析研究表明，九里桥组碳酸盐岩为未受淡水影响的正常海相沉积，后生成岩作用对该组碳酸盐岩的C、O同位素组成影响较小。该组沉积时期古海水温度在6.5℃一22℃之间变化，与该时期古纬度分析基本吻合。该组沉积期碳酸盐岩C同位素组成变化特征与海平面变化具有相关关系，6’3c值具有伴随海平面升高而增大，伴随海平面下降而减小的变化趋势。 该组碳酸盐岩主要形成于海水较浅的缓斜坡环境，根据风暴沉积旋回、叠层石造礁旋回和海绿石凝缩层沉积旋回等和其它露头层序地层特征，为该组划分出巧个副层序，它们分别代表了海进体系域、高水位体系域和低水位体系域的沉积，并构成一个相对完整的海进—海退旋回。 在该组沉积期有大量的宏体、微体浮游生物和造叠层石生物生存繁衍，宏体后生动物在该组沉积晚期也开始出现，它们分别在不同的沉积环境中留下了化石记录。对化石保存特征以及沉积环境变化的综合研究表明，不同生物对环境变化的适应能力不同，造叠层石生物能对该组沉积时期的环境变化作出及时调整，其它类型的生物对环境则具有较强的选择性和依赖性。关键词:碳酸盐岩，事件沉积，叠层石礁体，生物活动，沉积环境，新元古代，九里桥组， 淮南地区夕更多还原

【Abstract】 The Neoproterozoic Jiuliqiao Formation in Huainan region is 40-70m thick, consists of sandy, silty and dolomitic limestone. It has been taken as one perfect object for the research on the life evolution, the relationship between organisms and environments during the Neoproterozoic, because of the well outcropped strata, various depositional types, abundant stromatolite reefs, macroscopic alga, acritarchs and macroscopic worm-like organisms in the Formation.The event deposits, outcrop sequence stratigraphy, paleontology, stromatolite reefs and depositional geochemistry of the carbonatites have been studied, and the environment changing process and corresponding biological responsing characters were well discussed in this paper, some new evidences and information were appended to the Neoproterozoic biology, sedimentology and environmental sciences.From bottom to top, three parts of the Formation was subvided as: the lower sandy and silty limestone part (with molar-tooth-like veins, is 13-18m thick), the mid stromatolite limestone part (is 19-62m thick) and the upper sandy limestone part(with macroscopic fossils, is 7-10m thick), based on the characters of the lithology, event deposits, paleontology and correlation of different outcrops of the Formation.Different events, such as violent earthquakes during the early period, frequent strong storms and the maximum flooding events during the middle period, the abrupt environment changes and regression during the later period of the Jiuliqiao Time, had different influences on organisms. The violent earthquakes made few organisms survive during the early period; the storm events comprised the occasional stage during the early period, the frequent stage and the decreasing stage during the middle period and the quiet stage during the later period of the Jiuliqiao Time. Five typical storm deposition cycles were identified during the Jiuliqiao Time. The process from puissant to recessionary of the storm events could be correlated with such process: the stromatolite reefs becoming bigger, the micro and macro fossil become manifolding, the phenomena indicate that frequent storm events had negative influence on the organisms in Huainan region, while the stromatolite-made cyanobacteria had better adaptability than others during the Jiuliqiao Time.Abundant acritarchs were obtained from the Jiuliqiao Formation for the first time. The acritarch assemblage, which comprises Acanthomorphitae, Herkomorphitae, Pteromorphitae, Nematomorphitae, Sphaeromorphitae and many multicellular algal fragments, has seventeen form genus, fifteen species and thirteen species indeterminate. The assemblage has importantbiostratigraphy significance, because of it’s transitional characters from the Qingbaikou Period to the Sinian Period. The characters of acritarchs indicate that a new developing stage of the microplankton had come forth during the Jiuliqiao Time.The distribution characters of the macroscopic fossils, acritarchs and the stromatolite reefs in the Jiuliqiao Formation indicate that, the complicated biocommunity had been formed by abundant macro-organisms, micro-plankton and stromatolite-made cyanobacteria during this Time. The struggles for existence between different organisms had become obvious, and might resulted in the interbedded outcropping characters of the macroscopic fossils and acritarchs.The stromatolites in the Formation had such changing dendency: tuberosity, broken and forked shortprismatic in the lower part, complete and nonforked long-column in the mid part, tuberosity, complete forked shortprismatic in the upper part. The stromatolite reefs had such changing dendency: small scale lenticular and moundy in the lower part, large scale moundy in the mid part, and small scale lenticular in the upper part. The stromatolite reefs in the Formation were devided as the storm environment type, the transgression environment type and the regression environment type, eight reef-building cycles, which indicated the stromatolite-made cyanobacteria’s adapting process to different environments, we更多还原