【作者】 李晓波；

【导师】 张梅生；

【作者基本信息】 吉林大学 ， 古生物学与地层学， 2011， 博士

【摘要】 1大兴安岭北部晚中生代火山-沉积地层兴安岭群的划分和对比大兴安岭地区晚侏罗世至早白垩世火山—沉积地层分布很广,前人对其建立的“兴安岭群”基本含义明确,本文认为应继续作为一个正式“群”级地层单位使用。本文使用的兴安岭群含义如下：分布在大兴安岭及邻区的晚中生代火山—沉积地层,不整合于晚侏罗世之前形成的地层之上,为扎赉诺尔群及相当煤系地层整合或平行不整合覆盖。其使用范围限于整个大兴安岭地区(包括隆起区和盆地：大杨树盆地、海拉尔-塔木查格盆地、二连盆地),向西、向北为国界所限,向东至松辽盆地边界,向南至西拉木伦河并与燕—辽晚中生代火山岩带的金岭寺群、热河群等可以横向对比。长期以来,兴安岭群的组级地层单元划分存在较多争议,划分方案众多,对比关系混乱。为了解决这一问题,本文借鉴了前人划分地层小区的思路,根据兴安岭群的岩性组合及变化、发育时代等特征,以及研究程度、出露情况等其他因素,建立大兴安岭地区早白垩世地层的区划为：①龙江—呼玛小区(大兴安岭北部东坡),②阿尔山—额尔古纳小区(大兴安岭北部西坡),③海拉尔盆地小区,④二连盆地小区,⑤翁牛特旗—乌兰浩特小区(大兴安岭南部)。各小区的组级地层单元使用独立的地层系统以保持岩石地层单元的区域特性,尽量避免地层名称跨区使用易引起的争议和混乱。大兴安岭北部西坡阿尔山—额尔古纳小区的地层序列较为齐全,可作为地层对比的标尺,本文重新厘定的地层序列为：下亚群—塔木兰沟组(J2-3,基性火山岩)、吉祥峰组十木瑞组(J3-K1?,中酸性火山岩、火山碎屑岩),上亚群—瓦拉干组(K1,中基性火山岩)、上库力组(K1,中酸性火山岩、火山碎屑岩)、伊列克得组(K1,中基性火山岩夹煤系地层)。上述下亚群(160-131 Ma)总体可与冀北—辽西的金岭寺群对比,上亚群(130-110 Ma)可与热河群(不含沙海组和阜新组)对比,但不是完全的等时对比。下亚群上部的时代可能与热河群下部(张家口组、大北沟组)相当,但是从岩石地层格架的角度来看适宜划分在下亚群。兴安岭群纵向上至少发育三个分别从基性到酸性演化的火山作用旋回,每一个旋回的基性和酸性组合都存在一定程度的指状穿插(或同时异相)关系,构成双峰式火山岩组合。第一旋回相当于冀北—辽西的髫髻山期—张家口期两个火山旋回,所以也存在进一步划分的可能性,分别对应蒙古国东戈壁盆地的晚中生代同裂陷旋回最初的2个(SR1和SR2)；第二旋回相当于辽西义县期火山旋回；第三旋回相当于辽西大兴庄火山旋回以及松辽盆地营城期火山旋回。每两个顺次的旋回之间也不是截然的关系,有时有一定过渡性。本文定义和划分的兴安岭群还有一个重要的特点是湖相沉积十分发育,是中国海拉尔盆地、二连盆地、蒙古国东戈壁盆地等的主要生油层位,有些类型的火山岩(如：气孔玄武岩)也可能成为有利的油气储层。同期地层向东部松辽盆地以及黑龙江省东部逐渐变为陆相含火山—沉积岩及煤地层、海陆交互相含煤地层,具有形成天然气的条件和潜力。2生物地层和年代地层兴安岭群下亚群上部产热河生物群早期组合(Nestoria-Sentestheria组合,相当于冀北的Nestoria-Keratestheria叶肢介动物群),上亚群产热河生物群中期和晚期组合。都是与热河生物群分布核心区域(燕辽地区)非常相似的类型。龙江-呼玛小区的九峰山组下部产典型的热河生物群中期组合：Eosesthria-Ephemeropsis trisetalis-Lycoptera组合。阿尔山-额尔古纳小区的上库力组产热河生物群中期组合中的Arguniella, Lycoptera等化石。阿尔山-额尔古纳小区的伊列克得组产软骨硬鳞鱼类北票鲟科的Yanosteus sp和弓鳍鱼类中华弓鳍鱼科的Sinamia sp.,这一鱼类组合与辽西九佛堂组的鱼类组合相当,地层时代也相符。伊列克得组孢粉和植物大化石都反映了裸子植物比较占优势,总体面貌与Heer于1876年报道的俄罗斯阿穆尔地区(Amurlandes)植物群非常类似。本文总结统计了近期公开发表的兴安岭群火山岩高精度同位素年龄59个,结果表明其地质时代为160-110Ma,下亚群时代主要在160-140Ma之间,上亚群集中在130Ma-120Ma之间。整体在125Ma左右达到高峰,这一期火山岩在全区分布较广。兴安岭群的同位素年龄与整个中国东部的火成岩活动时代特征基本一致。因为国际年代地层表中侏罗系和白垩系界线年龄未定,而且岩石地层具有穿时普遍性特点,两个亚群分别对应但不绝对限定于晚侏罗世和早白垩世。3北票鲟科和中华弓鳍鱼科的古生物地理和地层对比意义中华弓鳍鱼科在早白垩世广泛分布于亚洲东部,在多个地方性鱼群中都有出现,说明Lycoptera-Peipiaosteus鱼群(包括酒泉盆地Jiuquanichthy鱼群)、Mesoclupea-Paraclupea鱼群(包括日本石徹白鱼群、胁野鱼群、和韩国洛东鱼群)以及泰国早白垩世鱼群有密切联系,是东亚地区早白垩世自成一个古生物地理区系的证据之一。北票鲟科可能只存在于热河生物群的北部分布区(大兴安岭北部、蒙古国、俄罗斯外贝加尔)和核心区(燕辽地区),说明它们有相对更紧密的水系联系和更相似的古环境背景。中华弓鳍鱼科化石已知时代延限为早白垩世B arremian-Albian期,在Aptian期达到了最大分布范围。广泛的分布、集中的时代延限、以及鲜明的鉴定特征,使得中华弓鳍鱼科化石非常有助于提高大区域地层对比的精度,或提供很好的验证,其中的中华弓鳍鱼属是亚洲东部大范围地层对比的标志化石之一。相比较中国西北、东南沿海、日本、韩国等其他热河生物群分布区,热河生物群北部分布区和核心分布区的脊椎动物组合最为接近。北部分布区到核心区的空间距离超过上述西部和东部至核心区的距离,具有相似的生物群可能因为它们具有更加相似的古地理和古气候背景来解释。它们都位于前人划分的晚侏罗世—早白垩世“兴安火山盆地区“,早白垩世“温带—温暖带植物群分布区”,晚侏罗世?—早白垩世“亚热带-暖温带半潮湿叶肢介动物地理区”,其他分布区都不在上述之内。不过,北部区和核心区早白垩世的古气候可能并没有前人认为的那么温暖,根据近期一些新的资料。4早白垩世陆地脊椎动物群的比较早白垩世的陆地生态系统中,具备特异埋藏特征的脊椎动物群在欧亚大陆和冈瓦纳大陆均有分布,它们是中国燕辽地区热河生物群、甘肃昌马盆地下沟动物群(属于热河生物群)、意大利Pietraroia生物群、西班牙Las Hoyas生物群、巴西Santana生物群和阿根廷Lagarcito翼龙动物群。具重要古气候、古生态意义的澳大利亚维多利亚极地动物群(Victorian Polar Biota)和俄罗斯外贝加尔早白垩世Baissa生物群(也属于热河生物群)都具备成为脊椎动物特异埋藏型化石库的潜力。热河生物群和澳大利亚维多利亚极地生物群虽然相隔甚远,生物群也没有密切的亲缘演化关系,但却各自繁衍了结构相似的陆地生态系统。中生代地球气候的大环境是温暖为主,导致维多利亚极地生物群虽然在早白垩世位处极地,却形成了与现今中、中高纬度气候相似的温带气候。燕辽—大兴安岭—外贝加尔地区热河生物群生存时期的古地理背景是大面积的火山构造高地,推测当时古海拔可能类似现今长白山地区。所以没有因位处中纬度而气候温暖,却因为古海拔的因素而存在一定时期寒冷的温带气候。古纬度和古海拔的各自影响,使得维多利亚极地生物群和热河生物群获得了相似的古气候条件,从而繁衍出相似的古生态系统。这种古气候控制因素的确立,再结合近期一些学者对热河生物群定量古气候研究的结果—热河生物群生存时期存在寒冷气候,可以解释关于“中生代中国东部高原”假说和热河生物群古生态特点存在所谓“矛盾”的问题。早白垩世这些特异埋藏动物群的形成,可能各自都有特殊的成因条件和机制,包括热河生物群的不同产地和层位,也要分别分析,避免一概而论。大兴安岭北部以及甘肃昌马盆地的一些剖面记录了早白垩世湖泊环境脊椎动物集群死亡事件,但地层和沉积特征显示没有受到火山作用的影响,事件发生的原因是否可用CO2驱动湖泊喷发模式解释需要今后进一步研究。今后寻找热河生物群化石不但要继续关注已经被证明是良好条件的火山—沉积地层,类似国外Santana和Las Hoyas生物群的碳酸盐岩型沉积条件也要充分重视。中国西部宁夏下白垩统六盘山群、甘肃下白垩统新民堡群中都有大量的湖相碳酸盐岩沉积,应该在这些地区注意是否存在含化石的纹层状碳酸盐岩。更多还原

【Abstract】 1. The Lithostratigraphic division and correlations of the Xinganling GroupThe Late Jurassic to Early Cretaceous volcano-sedimentary successions are widely distributed in the northern Great Xing’an Range area. Scientists named them Xinganling Group, and author of current thesis considered that the basic definitions of this group are realizing thus should be used keep on as a formal Group-level lithostratigraphic unit.The meanings of the Xinganling Group used in current thesis are as flowing:a series of late Mesozoic volcano-sedimentary successions distributed in Great Xing’an Range area and adjacent areas. The group developed unconformablely above the pre-Late Jurassic strata, and covered by the coal bearing Zhalainuoer Group and other comparable units. The extent of the group is mainly in Great Xing’an Range area (including uplifted areas and basins of Dayangshu Basin, Hailar-Tamsag Basin, and Erlian Basin). The western and northern extent is restricted by the national boundaries. The eastern extent arrived at the western edge of Songliao Basin. The southern extent lasted until at area of the Xilamulun River, where they joined to the Jinlingsi Group and Jehol Group mainly developed at Yan-liao areas (Northern Hebei and Western Liaoning).For a long time, the divisions of the formations of Xinganling Group are under dispute, there are many plans and their correlation relationships are consusion. In order to resolve this problem, current thesis refered to previrous scientists’works on the division of stratigraphic district, and considered the litho-associations, ages, status of previous works, and outcrop conditions, current thesis established a stratigraphic minor region division model:①Longjiang-Huma (eastern slope of the Great Xing’an Range);②Arshan-Argun (western slope of the range);③Hailar Basin;④Erlian Basin;⑤Wengniuteqi-Wulanhaote (southern of the range). Different stratigraphic nomenclature and divisions were used in each minor region, and this should be useful to avoid dispute and chaos on who to name the units.Since the Late Jurassic-Early Cretaceous successions in Aershan-Argun Minor Region are more complete and better understanded, thus the stratigraphic division model in this minor region has been chosen as a rule to be used in regional stratigraphic correlations. The sequence of the successions is as flowing:Lower Subgroup, Tamulangou Formation (J2-3, Basalt), Jixiangfeng Formation and Murui Formation (J3-K1?, trachyte, rhyodacite, pyroclasts); Upper Subgroup, Walagan Formation (K1, andicite, basalt), Shangkuli Formation (K1, trachyte, rhyodacite, pyroclasts, shales), Yiliekede Formation (K1, coal-bearing basalts andesitic basalts). The Lower Subgroup (160-131 Ma) as a whole could be correlated with the Jinlingsi Group which developed in North Hebei-West Liaoning, and the Upper Subgroup (130-110 Ma) could be correlated with the Jehol Group, but these relationships don’t meant isochronal correlation. The upper part of Lower Subgroup and the lower part of Jehol Group (Zhangjiakou Formation and Dabeigou Formation) have the close geological age, but it is feasible to put the prior into the Lower Subgroup, according to the Lithostratigraphic framework.The Xinganling Group could be subdivided into three volcanism cycles with each evolved from basic to acidic volcanics, lengthways. The basic and acidic volcanics of each cycle have a certain extent of finger interlude (synchrono-heteropic facies variety) relationships, hence, each composed of bimodal volcanic rock associations. The first cycle is correspond to the Tiaojishanian-Zhangjiakouan volcanic cycles in North Heibei-West Liaoning, therefore, would be possibly further subdivided into two cycles and each correlated to the first two late Mesozoic syn-rifting cycles in East Gobi Basin of Mongolia; The second cycle correlated to the Yixianian volcanic cycle in western Liaoning; The third cycle correlated the Daxingzhuangian volcanic cycle in western Liaoning and the Yingchengian volcanic cycle in the Songliao Basin. Each two in succession cycles could be divided sharply (completely), sometimes they have the transitional relationships.The Xinganling Group, defined and divided in current thesis, have a import character of composing many lacustrine sediments. Those lacustrine sediments are important oil-generation beds of Hailar Basin and Erlian Basin in China, and East Gobi Basin in Mongolia. Some kinds of volcanis, like the stomatic basalts, are likely to be the good oil-gas bearing beds. The homochronous strata extend to Songliao Basin and eastern Heilongjiang are gradually changed into non marine volcanic-sedimentary coal-bearing strata and marine-terrigenous coal-bearing strata, and they have the potential for generation of natural gas.2. Biostratigraphy and ChronostratigraphyThe upper part of Lower Xinganling Subgroup yield the fossils of the first evolutionary phase of Jehol Biota, the Chonchastracan fossils formed the Nestoria-Sentestheria assemblage, which correspond to the Nestoria-Keratestheria fauna in North Hebei. The Upper Xinganling Subgroup yields the fossils middle and late phases of Jehol Biota.The fossils from northern Great Xing’an Range area are quite same of those in the core-region (North Hebei-West Liaoning) of the Jehol Biota. At the Longjiang-Huma region, the lower part of Jiufengshan formation yield the typical fossils of middle phase Jehol Biota, which is Eosestheria-Ephemeropsis trisetalis-Lycoptera assemblage.At the Arshan-Argun region, the Shangkuli Formation yield the Arguniella and Lycoptera which all belongs to the middle phase Jehol Biota. The Yiliekede Formation yield two fishes, Yanosteus sp. and Sinamia sp. This fish assemblage correlated to the fish assemblage of Jiufotang Formation in western Liaoning, and their strata also have the same age. Both the microfossils (spore-pollen) and mega-plants from the Yiliekede Formation represent a gymnosperm dominated flora, whose appearance looks quite like the flora described by Heer in 1876 from the Amurlands of Russia.There are 59 isotope ages from the Xinganling Group volcanics been stated and analyzed. The conclusion is that the whole of the group spans from 160 Ma to 110 Ma. The Lower subgroup are mainly between 160 Ma to 140 Ma, and the Upper subgroup concentrated within 130 Ma to 120 Ma. The volcanism achieved the peak at 125 Ma, and volcanics generated at this phase widely distributed at the whole region. The isotope ages of Xinganling Group have the same chronological framework of eastern China Mesozoic volcanism. Because the absolute age at the boundary of Jurassic and Cretaceous had not finally confirmed in the ISC (International Stratigraphic Chart), and the lithostratigraphic units have an all-pervading characteristic of diachronism, thus the two subgroups separately correspond to but not firmly constrained within Late Jurassic and Early Cretaceous.3. Paleobiogeography and Significances on Stratigraphical Correlation of Peipiaosteidae and SinamiidaeSinamiidae is an extinct clad of the Amiiformes, Holostei. They had been discovered only from the Early Cretaceous sediments in eastern Asia, and they were important members of the Jehol Biota. The family is composed of three genus and eight species, and the Sinamia has the widest distribution among the entire genus of Jehol Vertebrates Fauna. The geographic distribution of the Family ranges to the most northern part of NE China to the north, ranges to the eastern of Thailand in Southeast Asia to the south, ranges to the Jiuquan Basin of Gansu Province to the west, and ranges to the middle part of Japan to the east. The Sinamiidae occurred in several local characteristic fish faunas, they are:the Lycoptera-Peipiaosteus Fish Fauna (including the Jiuquanichthy Fish Fauna in Jiuquan Basin) in North China, Northeast China, and part of Northwest China, the Mesoclupea-Paraclupea Fish Fauna (including the Itoshiro, Wakino Fish Fauna in Japan and the Nagdong Fish Fauna in South Korea), and the Early Cretaceous fish fauna in the eastern of Thailand. The Family’s wide distribution in the East Asia is one of the evidences to prove that the East Asia separately formed a paleobiogeographic region during Early Cretaceous. The Peipiaosteidae might exist only within the northern extent (northern Great Xing’an Range, Mongolia, Transbaikalia of Russia) and core-region of Jehol Biota, this implied that those areas ever had closer river systems and more similar paleoenvironment.As currently knows, Sinamiidae’s geologic range is Barremian-Albian, and they extended to the widest range of their distribution during the Aptian. The wide distribution, concentrated geologic range, and the cleared diagnostic characters made this kind of fossils quite helpful in enhancing the precision of stratigraphical correlation or providing a good validation.Be compared with other extents of Jehol Biota at western China, southeastern China, Japan, and Korea, the northern extent have the much more similar vertebrate assemblage toward that from core-region. Actually, the geographic distance between northern extent and core-region is longer than other extents with less similar biota. Thus, biota’s similarities would be controlled by their similar paleogeographic and paleoclimate backgrounds. For instance, they all belongs to the Late Jurassic to Early Cretaceous "Hinggan volcanic basins" and Early Cretaceous "N. China humid warm to temperate zone", Early Cretaceous "temperate-warm temperate floras", Late Jurassic? to Early Cretaceous "semi-tropical-warm temperate zone, semi-humidity", respondly with other extents not include those regions. However, the plaeoclimate might not such "warm" as they considered, according to some new evidences.4. A comparison of Early Cretaceous vertebrate faunas In the Early Cretaceous continental ecosystems, vertebrate faunas with unique taphnomic characters (Lagerstatten preservation quality) are distributed both on the Eurasia and Gondwana. They are Jehol Biota in North Hebei-West Liaoning; Xiagou Biota in Changma Basin, Gansu, which is a sub-biota belongs to Jehol Biota; Pietratoia Biota in Italy; Las Hoyas Biota in Spain; Santana Biota in Brazil; Lagarcito pterosaur fauna in Argentina, and most of them are exist within lacustrine environments. The Australian Victorian Polar Biota and Transbaikalian Baissa Biota (also a sub-biota of Jehol Biota) have the potential to be additional Lagerstattens.There was a long distance between Eastern Asian Jehol Biota and Australian Victorian Polar Biota during Mesozoic, and their biotas didn’t have much close evolutionary relationships. However, similar Early Cretaceous continental ecosystem frameworks were developed in two areas separately. The main and holistic climate circumstance of the earth is warm during the Mesozoic, this made the Victorian Polar Biota, which located at the southern polar region during Early Cretaceous, under went a wormer climate like that at nowadays middle or middle-high latitude, but not the climate as cold as that of nowadays polar region. North Heibei-West Liaoning-Great Xingan Range-Transbaikalia areas might be a huge volcanic high-lands, their paleo-altitude may resemble to present-day Changbai Mountain area of NE China. So that, those places which located at the paleo-middle latitude missed the regularly worm climate that such latitude area should be, and a certain period or times of cold climate afected those regions. Therefore, the paleo-latitude and paleo-altitude contributed separately to the similar climate conditions of Victorian Polar Biota and Jehol Biota, and then the similar paleoecosystems represented at two areas. The establish of this paleoclimate driving model, and with the recently published data on the quantitative analysis on the paleoclimate, which indicate that the Jehol Biota had under went certain times and period cold climate, could explain the so said "contradiction" between the "Mesozoic eastern China Plateau hypothesis" and the paleoecology of Jehol Biota, thus such "contradiction" might not exist.The formation of those Early Cretaceous lacustrine Lagerstatten of vertebrates, might related to each special conditions and mechanisms. Toward to the different localities of Jehol Biota, should analyze them differently, to avoid use only one thoughts. Some sections in the northern Great Xing’an Range and Changma Basin in Gansu, ecorded the vertebrates mass mortality events in the early Cretaceous lakes, but the stratigraphic and sedimentary characters show no sign of volcanism affect, weather they formed under the condition comparable to the model of CO2-driven lake eruptions should be further investigated.The paleontological studies on Jehol Biota in the future, should concern not only the volcanic-sedimentary strata which had been proved of good conditions for fossils’accumulation and preservation, but also the sedimentary types of lacustrine carbonates which yield Lagerstatten like Santana and Las Hoyas biotas. There are abundantly lacustrine sediments exist within the Lower Cretaceous Xinminpu Group in Gansu and Liupanshan Group in Ningxia, western China, thus the future works should devote more attentions to find fossilifeous laminated carbonates.更多还原