贵阳花溪早三叠世遗迹化石及其对二叠纪末生物大绝灭事件后生物复苏的启示?

报道了贵阳花溪下三叠统大冶组中14种遗迹属,它们包括Beaconichnus、Cosmorhaphe、Dendrorhaphe、Gyrochorte、Gordia、Micatuba、Mammillichnis、Megagrapton、Planolites、Palaeophycus、Phycodes、Phycosiphon、Rhizocorallium和Undichna。遗迹化石产出特征为以水平潜穴为主、浅的阶层分布（<4mm）、以觅食迹为主的遗迹组合和小型化的Planolites,这些特征表明经历了P-T事件之后,华南早三叠世浅海生态环境仍处于缺氧异常环境,这种环境直到早三叠世晚期才趋于正常。大冶组遗迹化石发展模式体现出海洋环境群落生态演替特征,造迹生物由早期单一多毛类蠕虫向物种丰富的多毛类发展,再到以甲壳纲动物在沉积物中开辟更大的生态空间和定居。这种绝灭后软躯体动物在崩溃生态系中的发展模式与贵州晚泥盆世弗拉期-法门期之交绝灭界线之上遗迹化石所表现的软躯体动物的演化特征相似。向三度空间开拓发展的复杂遗迹Rhizocorallium,Thalassinoides在绝灭前后世界范围内的分布表明,高纬度区软躯体动物的复苏比低纬度区要快。     

三叠纪末期全球生物大灭绝事件研究综述

三叠纪末期生物大灭绝是全球地质历史时期五大生物灭绝事件之一,它致使海洋生态系统中约53%的属和80%的种灭绝。显著灭绝的生物包括菊石类、牙形类、放射虫类和陆地四足动物,发生部分灭绝的生物包括腕足类、介形类、双壳类和珊瑚类等。中大西洋火成岩省（CAMP）的爆发与三叠纪末期生物大灭绝在时间上具有较高的一致性,其火山的高强度和大面积喷发被认为是导致此次灭绝事件发生的主要原因。CAMP爆发释放出大量的CO2、SO2和CH4等气体,一方面温室效应促使海平面升高,物种栖息地面积减少、海洋酸化和海洋缺氧等事件直接威胁着海洋和陆地生物的生存环境;另一方面温室效应亦会引发全球性森林火灾,造成陆地植物减少,大量植物碳屑注入海洋使其发生富营养化,又因伴随海洋酸化作用（碳酸化和硫酸化）,海洋古生产率发生崩溃。不同地质时期生物大灭绝的发生往往伴随着剧烈的环境变化,在三叠纪末生物大灭绝期,这些变化多表现为古大气成分和古气温动荡、古火灾频繁、海洋酸化、海平面升高和海水缺氧等,它们之间的综合作用最终导致三叠纪末期全球生态系统失稳。在全球多个三叠纪—侏罗纪之交（TJB）剖面均可以识别出3次明显的碳同位素负偏移,最显著的1次发生于瑞替期末,早于TJB。上述情况说明,三叠纪末期生物大灭绝虽然是全球性事件,但并不是1次发生的,具有分阶段性、非同步性、区域性和有选择性等特点。     

三叠纪末期全球生物大灭绝事件研究综述

三叠纪末期生物大灭绝是全球地质历史时期5大生物灭绝事件之一,它致使海洋生态系统中约53%的属和80%的种灭绝。显著灭绝的生物包括菊石亚纲、牙形类、放射虫目和陆地四足动物,发生部分灭绝的生物包括腕足动物门、介形亚纲、双壳纲和珊瑚纲等。中大西洋火成岩省(CAMP)的爆发与三叠纪末期生物大灭绝在时间上具有较高的一致性,其火山的高强度和大面积喷发被认为是导致此次灭绝事件发生的主要原因。CAMP爆发释放出大量的CO₂、SO₂和CH₄等气体,一方面温室效应促使海平面升高,物种栖息地面积减少、海洋酸化和海洋缺氧等事件直接威胁着海洋和陆地生物的生存环境;另一方面温室效应亦会引发全球性森林火灾,造成陆地植物减少,大量植物碳屑注入海洋使其发生富营养化,又因伴随海洋酸化作用(碳酸化和硫酸化),海洋古生产率发生崩溃。不同地质时期生物大灭绝的发生往往伴随着剧烈的环境变化,在三叠纪末生物大灭绝期,这些变化多表现为古大气成分和古气温动荡、古火灾频繁、海洋酸化、海平面升高和海水缺氧等,它们之间的综合作用最终导致三叠纪末期全球生态系统失稳。在全球多个三叠...     

西藏海相三叠系-侏罗系界线及晚三叠世生物绝灭事件研究

1998—2004年间在西藏聂拉木、林周、墨竹工卡和洛扎等地进行的三叠系/侏罗系界线地层研究表明,西藏隆子县和洛扎县尚未发现具有连续菊石层序的三叠系/侏罗系界线地层剖面。拉萨以北地区广泛分布的火山岩时代确定为晚三叠世—早侏罗世早期,这有助于解释晚三叠世末期生物绝灭与晚三叠世岩浆侵入和大规模的火山活动有关,但T/J界线尚待精确限定。聂拉木县格米格剖面是特提斯地区唯一未曾“压缩”的三叠系/侏罗系界线地层剖面,具有瑞替阶MARSHI菊石带、赫塘阶Tibeticum、Callyphyllum和Pleuro-notum菊石带。格米格剖面三叠系/侏罗系界线碳稳定同位素曲线记录了晚三叠世瑞替阶末期(Marshi菊石带)突然的负偏移,它很有可能和晚三叠世末期的由超级温室效应所产生的生物绝灭事件相对应。     

Behavior of lophophorates during the end-Permian mass extinction and recovery

The end-Permian mass extinction devastated most marine communities and the recovery was a protracted event lasting several million years into the Early Triassic. Environmental and biological processes undoubtedly controlled patterns of recovery for marine invertebrates in the aftermath of the extinction, but are often difficult to single-out. The global diversity and distribution of marine lophophorates during the aftermath of the end-Permian mass extinction indicates that stenolaemate bryozoans, rhynchonelliform brachiopods, and lingulid brachiopods displayed distinct recovery patterns.Bryozoans were the most susceptible of the lophophorates, experiencing relatively high rates of extinction at the end of the Permian, and becoming restricted to the Boreal region during the Early Triassic. The recovery of bryozoans was also delayed until the Late Triassic and characterized by very low diversity and abundance. Following the final disappearance of Permian rhynchonelliform brachiopod survivors, Early Triassic rhynchonelliform brachiopod abundance remained suppressed despite a successful re-diversification and a global distribution, suggesting a decoupling between global taxonomic and ecological processes likely driven by lingering environmental stress.In contrast with bryozoans and rhynchonelliforms, lingulid brachiopods rebounded rapidly, colonizing shallow marine settings left vacant by the extinction. Lingulid dominance, characterized by low diversity but high numerical abundance, was short-lived and they were once again displaced back into marginal settings as environmental stress changed through the marine recovery. The presence in lingulid brachiopods of the respiratory pigment hemerythrin, known to increase the efficacy of oxygen storage and transport, when coupled with other morphological and physiological adaptations, may have given lingulids a survival advantage in environmentally stressed Early Triassic settings.     

粤东晚三叠世小水组——早侏罗世金鸡组古气候及构造背景的矿物和地球化学记录

对揭西灰寨剖面上三叠统小水组和惠州黄洞剖面下侏罗统金鸡组采集的泥岩和砂岩样品进行了全岩分析和ICP-MS微量、稀土元素测试和矿物成分分析,根据元素含量及其比值的变化,提出了粤东揭西地区晚三叠世小水组和惠州地区早侏罗世金鸡组水体整体为还原、厌氧环境,以干燥炎热气候为主。小水组w(∑REE)较大,轻稀土富集(LREE/HREE为10.86和15.63),重稀土较稳定(w(∑HREE) 为6.09×10^-6和7.99×10^-6),Eu负异常(δEu为0.67和0.87);金鸡组轻稀土富集(LREE/HREE=7.29~10.03),重稀土较稳定(w(∑HREE)为(15.39~19.72)×10^-6),Eu负异常(δEu=0.59~0.65)。泥岩稀土元素分布模式图和源岩判别图解显示,小水组和金鸡组源岩来自上地壳的沉积岩、花岗岩和玄武岩,小水组下部样品沉积物源岩较上部要深,金鸡组上部沉积物源岩较中下部要深。Dickinson图解、K₂O/Na₂O-w(SiO₂)、Zr-Th、La-Th-Sc、Th-Co-Zr/10判别图解和稀土元素特征值显示,晚三叠世揭西地区的构造背景为弧后伸展盆地,有被动大陆边缘特性,但也有大陆岛弧(由安第斯大陆边缘弧转变而来)的特性,其物源来自火山弧造山带。早侏罗世黄洞地区为弧后挤压盆地,具有被动陆缘特性,沉积物物源来自于切割的岩浆弧。     

Unusual intraclastic limestones in Lower Triassic carbonates and their bearing on the aftermath of the end-Permian mass extinction

Flat pebble conglomerates were a common carbonate facies in Cambrian to Early Ordovician open marine settings, but they become extremely rare in these environments after this time. However, the Early Triassic witnessed an anachronistic reappearance of flat pebbles, together with other intraclast types, in a range of carbonate depositional settings. In south China, flat pebble conglomerates are encountered in storm-dominated, platform carbonates to deep basinal settings, while prefossilized bivalve intraclasts and flat pebbles are common in mid-ramp facies of northern Italy. The emplacement mechanisms of the intraclast-bearing beds appear to have been diverse and to have included basinal turbidity flows and storm-generated hyperconcentrated flows: true storm beds, deposited under combined flow conditions, are rare. The cause of the widespread early lithification implied by the Early Triassic intraclasts appears to have been twofold: suppression of bioturbation, allowing the preservation of thin beds, and rapid submarine lithification. Both features appear to be a response to the widespread development of benthic dysoxia/anoxia during and following the end-Permian mass extinction. This event appears to have temporarily recreated the conditions that pertained in Cambro-Ordovician shelf seas. Flat pebble conglomerates may, therefore, constitute a proxy indicator of stressed environmental conditions associated with global anoxic/dysoxic events.     

Early Evolution of Apocrita(Insecta,Hymenoptera)as Indicated by New Findings in the Middle Jurassic of Daohugou,Northeast China

<正>The classification and phytogeny of the basal Vespina(=Orussoidea+Apocrita)are reconsidered based primarily on rich and well preserved material from the Middle Jurassic of Daohugou in Inner Mongolia,China. Comparatively smooth morphological transitions are traced from a Xiphydriidae-like ancestor toward Orussoidea via the Jurassic family Karatavitidae,and through Karatavitidae and the Jurassic and Early Cretaceous family Ephialtitidae independently to Stephanidae,to Evanioidea,and,via the extinct Jurassic Kuafuidae fam.nov.to the remaining Apocrita.New hypothesis is proposed concerning development of the characteristic wasp-waist of Apocrita,which is supposed to appear independently and in different ways in Evanioidea and in the rest of Apocrita.As a result,six infraorders are proposed for the suborder Vespina with the following taxonomic structure:infraorder Orussomorpha including the only superfamily Orussoidea(Karatavitidae+Paroryssidae + Orussidae),infraorder Stephanomorpha with the only superfamily Stephanoidea(Ephialtitidae+Stephanidae), infraorder Evaniomorpha with the only superfamily Evanioidea of traditional composition,infraorder Ceraphronomorpha with the superfamilies Ceraphronoidea s.str.and monotypical Megalyroidea and Trigonaloidea,and the infraorders Proctotrupomorpha,Ichneumonomorpha,and Vespomorpha of traditional composition.The family Kuafuidae is unplaced to infraorder because it is putatively paraphyletic with respect to Ceraphronomorpha,Proctotrupomorpha,Ichneumonomorpha and Vespomorpha.Described as new are Karatavites junfengi sp.nov,Praeratavites wuhuaensis sp.nov.,P.perspicuus sp.nov.,Postxiphydria daohugouensis gen.et sp.nov.,P.ningchengensis gen.et sp.nov.,Postxiphydroides strenuus gen.et sp.nov.,Praeratavitoides amabilis gen.et sp.nov.,Proapocrtius densipediculus sp.nov.,P.sculptus sp.nov.,P.longantennatus sp.nov., P.formosus sp.nov.,P.atropus sp.nov.,P.elegans sp.nov.,Stephanogaster pristinus sp.nov.,Asiephialtites lini sp. nov.,Praeproapocritus vulgatus gen.et sp.nov.,Sinaulacogastrinus solidus gen.et sp.nov.,Sinevania speciosa gen. et sp.nov.,Eonevania robusta gen.et sp.nov.,Kuafua polyneura gen.et sp.nov.(all from the Middle Jurassic of Daohugou),as well as Kuafuidae fam.nov.including Kuafua gen.nov.as well as Arthrogaster Rasnitsyn,1975,and Leptogastrella Rasnitsyn,1975 from the Upper Jurassic of Karatau in Kazakhstan.     

鱼粪化石特征对早侏罗世托阿尔期湖泊生态系统的启示:以川东大安寨段为例*

早侏罗世托阿尔期早期大洋缺氧事件(Toarcian Oceanic Anoxic Event,~183.8 Ma)是一次全球性的多幕式生物—环境事件,其在四川盆地下侏罗统自流井组大安寨段亦有显示。对采集自川东北地区大安寨段的鱼粪化石进行形态学描述和内含物分析,发现鱼粪化石中含有大量的磷质成分,多为未经消化的鱼骨化石,另有大量介壳类化石与有机质混杂在一起。据露头岩性和显微薄片特征认为: (1)粪化石呈螺旋状,生产该粪化石的鱼类为大型肉食性鱼类,其喜食小型鱼类和软体动物等,推测可能是肺鱼类(角齿鱼);(2)鱼粪化石形成于开放型淡水湖泊中的半深湖—深湖区,其中湖泊表层含氧量丰富,主要由生产者、消费者构成了研究区早侏罗世托阿尔期大型湖泊生态系统,食物链较为复杂,而湖底为水动力条件较弱的还原环境。该研究成果可为早侏罗世托阿尔期大洋缺氧事件在湖泊中的沉积响应及生态影响研究提供依据。     

Early Jurassic rift structures associated with the Soapaga and Boyacá faults of the Eastern Cordillera, Colombia: Sedimentological inferences and regional implications

The NW-trending Bucaramanga fault links, at its southern termination, with the Soapaga and Boyacá faults, which by their NW trend define an ample horsetail structure. As a result of their Neogene reactivation as reverse faults, they bound fault-related anticlines that expose the sedimentary fill of two Early Jurassic rift basins. These sediments exhibit the wedge-like geometry of rift fills related to west-facing normal faults. Their structural setting was controlled further by segmentation of the bounding faults at approximately 10 km intervals, in which each segment is separated by a transverse basement high. Isopach contours and different facies associations suggest these transverse anticlines may have separated depocenters of their adjacent subbasins, which were shaped by a slightly different subsidence history and thereby decoupled. The basin fill of the relatively narrow basin associated with the Soapaga fault is dominated by fanglomeratic successions organized in two coarsening-upward cycles. In the larger basin linked to the Boyacá fault, the sedimentary fill consists of two coarsening-upward sequences that, when fully developed, vary from floodplain to alluvial fan deposits. These Early Jurassic rift fills temporally constrain the evolution of the Bucaramanga fault, which accommodated right-lateral displacement during the early Mesozoic rift event.     

Conodont biostratigraphy across the Permian–Triassic boundary at the Dawen section, Great Bank of Guizhou, Guizhou Province, South China: Implications for the Late Permian extinction and correlation with Meishan

Several continuous Permian–Triassic boundary (PTB) sections are well exposed in the interior of the Great Bank of Guizhou (GBG) on the east limb of the Bianyang syncline, Luodian County, Guizhou Province, South China. Fourteen conodont taxa are identified, including Clarkina kazi, Clarkina lehrmanni n. sp., Clarkina taylorae, Clarkina zhejiangensis, Hindeodus eurypyge, Hindeodus inflatus, Hindeodus sxlatidentatus, Hindeodus parvus erectus, Hindeodus parvus parvus, Hindeodus postparvus, Hindeodus praeparvus, Hindeodus typicalis, Isarcicella staeschei, and Merrillina ultima based on a detailed study of the Permian-Triassic interval at the Dawen section. The first occurrence (FO) of H. parvus parvus in the lower Daye Formation, at about 7.45 m above the contact surface between the Upper Permian skeletal packstone and a calcimicrobial framestone unit, is correlated with the Permian–Triassic boundary; the occurrence of H. eurypyge, H. praeparvus and M. ultima immediately below and H. postparvus above the interval supports this interpretation. A morphometric analysis of 31 Hindeodus specimens helped distinguish H. parvus erectus from H. parvus parvus and H. postparvus. Correlation with the Meishan section (PTB GSSP) using both conodont biostratigraphy and carbon isotopes, indicates that the major extinction at the two localities is simultaneous and coincides with the top of the skeletal packstone at Dawen. The contact between the skeletal packstone and the calcimicrobialite is very irregular and has previously been interpreted as a dissolution surface and correlated with a surface in the lower part of bed 27 at Meishan. Our results confirm this interpretation and reveal that the dissolution event postdated the extinction.