Late Jurassic-Early Cretaceous Erg Deposits in the Mengyin Basin, Western Shandong Province, China: Inferences about the Wind Regime and Paleogeography

The Late Jurassic-Early Cretaceous Santai Formation, sporadically distributed in western Shandong Province, comprises terrestrial alluvial-eolian successions, which records regional wind patterns and paleogeography in eastern North China. This paper conducts an analysis of eolian stratification, bounding surfaces, facies architecture and paleowind direction of the Santai Formation in the east of the Mengyin Basin, western Shandong Province. Three basic types of eolian stratification are recognized in the Santai Formation, including grainflow strata, wind ripple strata and adhesion strata, and have been grouped into eolian dune and interdune facies associations. The occurrences of reactivation surfaces and superimposition surfaces within eolian dune deposits indicate active compound dunes or draas. The association of adhesion strata with grainflow or windripple strata is the development of a wet eolian system. Cross-strata dip direction indicates different paleowind directions from the lower to the upper part of the Santai paleoerg. The lower part of the paleoerg was characterized by paleowinds blowing from northwest to northeast, whereas the upper part was under the influence of paleowinds consistently towards east to northeast. The identified changes in wind directions possibly suggest wind regime shifts from monsoon circulation to westlies of planetary wind system, which may be related with the collapse of the East China Plateau during the Late Jurassic to Early Cretaceous.

Late Jurassic and Early Cretaceous Radiolarians from Zhilong,Gyangse,Tibet

Abundant well-preserved Late Jurassic-Early Cretaceous radiolarian fossils were extracted from 31 bedded green chert samples collected from Zhilong section,Gyangse,southern Tibet.This

Changes of taxonomical composition of Late Jurassic-Early Cretaceous palynofloras of Bureya Basin,Russia

The changes of taxonomical composition of the Late Jurassic-Early Cretaceous palynofloras are revealed,in the upper stream of Bureya River in Bureya Basin.The palynofloras are dominated as follows:the Berriasian one by ferns(Cyatheaceae,Dicksoniaceae,Osmundaceae),Classopollis and bisaccate pollen;the Valanginian-Hauterivian one by ferns(Cyatheaceae,Dicksoniaceae),Ginkgocycadophytus and bisaccate pollen;the Barremian one by ferns(Cyatheaceae,Dicksoniaceae);the Aptian one by ferns(Cyatheaceae,Dicksoniaceae,Gleicheniaceae) and Ginkgocycadophytus;and the Albian one by ferns(Schizaeaceae) and bisaccate pollen.In the Albian the floral diversity raises with the angiosperms appearing.

A Titanosaurian Sauropod Dinosaur with Opisthocoelous Caudal Vertebrae from the Early Late Cretaceous of Liaoning Province, China

We describe a new titanosaurian sauropod dinosaur, Borealosaurus wimani gen. et sp. nov., based on a distinctive mid-distal caudal vertebra from the early Late Cretaceous Sunjiawan Formation exposed in the Shuangmiao village of Beipiao in Liaoning, China. We provisionally refer an isolated tooth crown, a middle caudal vertebra, and a right humerus from the same locality and horizon to this taxon. Borealosaurus is distinguished from other sauropods in its possession of opisthocoelous mid-distal caudal vertebrae. The occurrence of opisthocoelous caudals in Borealosaurus and the Mongolian sauropod Opisthocoelicaudia raises the possibility that these taxa pertain to an as-yet unrecognized titanosaurian subclade endemic to the Cretaceous Asia.

A New Titanosauriform Sauropod from the Early Late Cretaceous of Dongyang,Zhejiang Province

A new titanosauriform sauropod Dongyangosaurus sinensis gen. et sp. nov. from the early Late Cretaceous of Dongyang County, Zhejiang Province, is erected based on a partial postcranial skeleton. It is characterized by complex laminae on the lateral surface of the neural spines and postzygapophyses of dorsal vertebrae, a distinct fossa on the ventral surfaces of the prezygapophyses of dorsal vertebrae, distinct fossae are also present on the lateral surface of the postzygapophysis of anterior caudal vertebrae; pubis is shorter than ischium, the small obturator foramen of pubis elongated, and nearly closed. The lamina complexity of dorsal vertebrae in Dongyangosaurus indicates that a higher diversity of titanosauriformes occurred during the early Late Cretaceous in China.

Discovery of Fossil Charophytes from the Late Triassic Xujiahe Formation and Early Jurassic Lower Yimen Formation, Sichuan Province, and Its Significance

This paper describes the fossil charophytes collected from the Late Triassic Xujiahe Formation in Dazuand Early Jurassic Lower Yimen Formation in Xichang, Sichuan Province, and their significance. Up to now,papers dealing with fossil charophytes of the Late Triassic, especially of the Early Jurassic, have been rarelypublished. The description of the two new species of Porochara, P. dazuensis and P. xichangensis, and theirfossil assemblage not only provides an important basis for classification and correlation of red beds insouthwestern China but reveals for the first time the features of the charophyte flora of the Late Triassic-EarlyJurassic in the area, thus offering valuable data for the establishment of Triassic and Jurassic charophyte fossilzones in China.

Clay Minerals of the Middle Jurassic Through Lower Cretaceous in Guangyuan Area,Northern Sichuan:Implications to Paleoclimate

Clay mineral analyses of the Middle Jurassic through the Early Cretaceous sedimentary rocks from the Guangyuan-Jian’ge section,Sichuan Basin (southwestern China)were undertaken in this article, which is aiming to reconstruct the palaeoclimate of the area.Relative contents of the four clay minerals, smectite(25.8%-1.0%-46.8%),kaolinite(31.0%- 12.5%-12.6%),illite(31.3%-68.0%-28.0%)and chlorite(11.8%-8.5%-12.6%),as the target clay minerals,illite crystalline index(0.26-0.31-0.27)and chemical index(0.62-0.66-0.79)are used as indicator of paleoclimate.It is indicated that changes of

Early Cretaceous Tectonism and Diatoms in Korea

The Early Cretaceous Sindong Group, a non-marine molasse, unconformably overlies the folded earliest Cretaceous Myogok Formation. The tectonism that folded the Jaseong Synthem including the Myogok and other formations is here called the Nakdong-Jaeryeonggang （N-J） tectonism. The Oknyeobong and Dabokni Formations are discussed to show that they belong to the Jaseong Synthem. The Dabokni Formation yielded fossil diatoms whose age has been referred as the ＂earliest Cretaceous＂ based on the geologically constrained age of the fossil-bearing deposit. The age of the N-J tectonism appears Barremian as it is between the Hauterivian Myogok Formation and the Aptian Sindong Group with the TPN （Trigonioides-Plicatounio-Nippononaia） fauna. The N-J tectonism, an orogeny, quite deformed pre-Aptian strata in Korea, but can hardly find its reported equivalent in NE China. A revised correlation table shows that the Jaseong- Sindong sequence corresponds to the Jehol Group of China. The Sindong-Hayang transition was characterized by basin migration and dextral rotation probably caused by the Tan-Lu fault system in a broad sense.

Androecium of Archaefructus,the Late Jurassic Angioperms from Western Liaoning,China

Androecium of the earliest known flowering plant Archaefructus liaoningensis was found from the Upper Jurassic Jianshangou Formation of western Liaoning, China. The androecium consists of numerous stamens bearing in pair on the reproductive axes below conduplicate carpels. The stamens are composed of a short filament and basifixed anther for each. Monosulcate pollen in situ are found from the anthers. The characters of the androecium reveals that Archaefructus are probably protandrous, and the paired stamens and monosulcate pollen appear to indicate that Archaefructus, as primitive angiosperms,might be derived from extinct seed -ferns during the Older Mesozoic. Archaefructus is considered Late Jurassic in age.

Late Jurassic to early Cretaceous magnetostratigraphy of scientific drilling core LK-1 in the Lingshan Island of Riqingwei Basin,eastern China

The Sulu orogenic belt is an uplift zone that was formed in the Late Triassic.Several Jurassic to Cretaceous sedimentary successions have been recognized within the Sulu orogenic belt in recent studies,including outcrops that are considered to be related to the newly discovered Riqingwei Basin.This basin has been the focus of extensive study due to its continuous Cretaceous rock sequence,geological location and petroleum resource potential.However,the lack of a consolidated chronology for the strata has precluded a better understanding of stratigraphy,tectonic evolution and resource potential of the Riqingwei Basin.Here,we present the results of a new magnetostratigraphic study of the continental scientific drilling borehole LK-1,which is located on Lingshan Island,offshore Shandong province,eastern China.The goals of this study are to(1)refine the Late Jurassic to Early Cretaceous chronostratigraphic framework of the Riqingwei Basin,and(2)investigate the location of the J/K boundary in the Borehole Core LK-1.The observed patterns of the paleomagnetic polarity zone in the LK-1 borehole correlate well with the geomagnetic polarity time scale(GPTS),and the continuous magnetostratigraphy profile defined in this core indicates an age ranging from 146.5 to 125.8 Ma for the samples interval.The sediment accumulation rates(SAR)of LK-1 show one period of high SAR(~10.5 cm kyr^(-1))at 135.3–130.6 Ma and two periods of low SAR(~4.8 and~2.2 cm kyr^(-1))at145.7–135.3 and 130.6–125.8 Ma,respectively.In addition,the magnetostratigraphic results suggest that the Jurassic-Cretaceous(J/K)boundary of the LK-1 is located within the magnetozone N21.2 n(~1254 m).This comprehensive geochronologic framework provides a good correlation of the marine Upper Jurassic to Lower Cretaceous strata in the Riqingwei Basin to other marine strata and continental sequences,in addition to providing a foundation for the study of the structural evolution of eastern China.

羌塘盆地中生代岩相古地理研究新进展

由于资料的欠缺和分布的不均衡,羌塘盆地构造-岩相古地理研究程度总体不高,不能为烃源岩和储层的分布预测提供依据。基于盆地属性、沉积体系及组合-耦合关系的研究,解决了资料丰富区域沉积相解释的多解性、资料缺少区域沉积相预测缺乏沉积模式指导的问题,取得以下3方面的成果和认识:(1)系统梳理了可可西里—金沙江洋、班公湖—怒江洋、龙木错-双湖洋的闭合史,明确了羌塘盆地属性,指出北羌塘地块在晚三叠世—早白垩世经历了复合前陆盆地、陆内弱挤压残留海盆地、褶皱-冲断快速抬升剥蚀3个构造演化阶段,南羌塘地块在晚三叠世—早白垩世经历了被动陆缘、活动陆缘、褶皱-冲断快速抬升剥蚀3个构造演化阶段,明确了8个关键沉积时期的盆地属性。(2)基于盆地属性、沉积体系及组合-耦合关系,系统恢复了羌塘盆地晚三叠世—早白垩世10个关键地质时期的构造-岩相古地理背景,揭示了构造对沉积的控制作用,提高了资料缺少区域沉积相预测的准确度。(3)明确了烃源岩和储层发育的构造-岩相古地理背景,认为上三叠统波里拉组—巴贡组烃源岩的分布受控于前陆坳陷、被动陆缘深水陆棚等构造单元,下侏罗统曲色组烃源岩的分布受控于弧后伸展盆地、陆内弱挤压残留海盆地等构造单元,中侏罗统布曲组白云岩储层分布于台缘带。上述成果将为羌塘盆地油气资源潜力的认识和评价提供依据。

Changes of Late Mesozoic Tectonic Regimes around the Ordos Basin(North China)and their Geodynamic Implications

A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stress evolution was established from the field analyses of fault kinematics and constrained by stratigraphic contact relationships. The results show alternation of tectonic compressional and extensional regimes. The Ordos Basin and its surroundings were in weak N-S to NNE-SSW extension during the Early to Middle Jurassic, which reactivated E-W-trending basement fractures. The tectonic regime changed to a multi-directional compressional one during the Late Jurassic, which resulted in crustal shortening deformation along the marginal zones of the Ordos Basin. Then it changed to an extensional one during the Early Cretaceous, which rifted the western, northwestern and southeastern margins of the Ordos Basin. A NW-SE compression occurred during the Late Cretaceous and caused the termination of sedimentation and uplift of the Ordos Basin. This phased evolution of the late Mesozoic tectonic stress regimes and associated deformation pattern around the Ordos Basin best records the changes in regional geodynamic settings in East Asia, from the Early to Middle Jurassic post-orogenic extension following the Triassic collision between the North and South China Blocks, to the Late Jurassic multi-directional compressions produced by synchronous convergence of the three plates （the Siberian Plate to the north, Paleo-Pacific Plate to the east and Lhasa Block to the west） towards the East Asian continent. Early Cretaceous extension might be the response to collapse and lithospheric thinning of the North China Craton.

Late Mesozoic Chresmodids with Forewing from Inner Mongolia, China (Polyneoptera: Archaeorthoptera)

Three new species of Chresmodidae are described. They belong to two different genera： Chresmoda multinervis sp. nov., Chresmoda shihi sp. nov. and Jurachresmoda sanyica sp. nov.. A study of the forewing venation is provided. Longitudinal veins are mostly parallel; costal area is broad at the basal and narrowing distally; ScP is probably extending close to the wing apex; R is parallel at length to ScP; MA is running close to R, with two long parallel branches; MA branched-off basally; while MP is not branched until the middle of the wing. However, the important basal part of MP and CuP is poorly preserved. In addition, unique fringing hairs on the mid legs of C. shihi sp. nov. and J. sanyica sp. nov. are described and compared with Jurachresmoda gaskelli Zhang, Ren and Shih, 2008.

Plants of Leptostrobus Heer （Czekanowskiales） from the Early Cretaceous and Late Triassic of China, with Discussion of the Genus

Investigation of the Mesozoic seed plant Leptostrobus Heer from the Yangcaogou Formation of the Late Triassic and the Yixian Formation of the Early Cretaceous, Liaoning Province, China, provides new Insight Into Its general morphology and geographical distribution. The materials of L. cancer from the Yixian Formation described herein are later than all the past findings of this species and add to the record of L. cancer during the Early Cretaceous. Based on well-preserved specimens, the specific diagnosis Is slightly emended and the reconstructlon of L. cancer Is perfected. The materials from the Yangcaogou Formation of the Late Triassic are placed in L. spheericus, in addition, we review the history of investigation of the genus Leptostrobus since its establishment in 1876 and discuss the main characteristics of each species.

The Late Mesozoic Orogenic Processes of Mongolia-Okhotsk Orogen: Evidence from Field Investigations into Deformation of the Mohe Area, NE China

Based on field investigation in 1999, two deformational domains with d ifferent dynamics have been distinguished from the Jurassic geological outcrops in the Mohe area of NE China, i.e. northern ductile and southern plastic-brittl e ones. Their deformational features are stated in this paper. And then, three st ages of structural deformation of the area relative to the late Mesozoic orogeni c processes of Mongolian-Okhotsk orogen are reconstructed as follows, (1) south w ards thrusting in the middle-late Jurassic, (2) eastwards thrusting and strike -s lipping parallel to the orogen in the late Jurassic, and (3) southeastwards thru sting in the early Cretaceous.

New Fossil Beetles of the Family Elateridae from the Jehol Biota of China(Coleoptera:Polyphaga)

Two new species of elaterids assigned to two new genera with intriguing fossa on prosternum are described and illustrated： Bilineariselaterfoveatus gen. et sp. nov. and Curtelater wui gen. et sp. nov. from the Upper Jurassic-Lower Cretaceous Yixian Formation of western Liaoning, China. The origin of the clicking mechanism in these beetles and the systematic position of the two genera are briefly discussed.

A paleoisthmus linking southern South America with the Antarctic Peninsula during Late Cretaceous and Early Tertiary

Paleontological and stratigraphical data indicate that a link between terminal southern South America and the Antarctic Peninsula probably was an irregularly narrow continuous land from Late Cretaceous （Campanian） through the Eocene period. In paleogeographical feature it is more like modern Isthmus of Panama. A paleoisthmus called the isthmus of Scotia is hypothesized as a type of connection between them. It lasted about 35 Ma and extended about 700\900 km long and 100\200 km wide. This isthmus played an important role in biotic dispersal and migration among South America, Antarctica, Australia and New Zealand blocks during this interval.

商丹俯冲增生带南缘土地沟–池沟地区侵入岩形成时代及地质意义

位于商丹俯冲增生带南缘山阳–柞水地区的侵入岩类在形成时代主要集中在新元古代(885~621 Ma)和中晚三叠—早白垩世(233~132 Ma)2个阶段,且后者多为秦岭造山带印支期—燕山期造山活动的产物。该构造带内土地沟至池沟地区出露有部分与成矿作用有关的小岩体,锆石LA–ICP MS U–Pb同位素测年结果表明其形成时代为144.4~158.8 Ma,属于晚侏罗世—早白垩世侵入岩类。岩石地球化学特征显示出富集大离子亲石元素,亏损高场强元素,高Sr、低Y的特征。结合区域岩浆岩演化研究,可以认为土地沟–池沟地区晚侏罗—早白垩世侵入岩类的形成可能与西太平洋活动应力作用以及区内的北西向构造系统约束具有密切关联。受此影响,以中南秦岭地区在后碰撞–后造山阶段拆沉和幔源物质上涌作用下,地壳物质发生重熔从而在山阳–柞水一带形成一系列中酸性侵入岩类。

内蒙古中东部玛尼吐组火山岩形成时代及其大地构造环境

玛尼吐组广泛分布在内蒙古中东部地区,长期以来与满克头鄂博组和白音高老组的地质时代被定为晚侏罗世,然而前人在玛尼吐组中发现Nestoriapissovi化石,并认为是早白垩世冀北阶的带化石,同位素年代学结果差异也较大,而且形成的大地构造环境仍然存在争论。因此,笔者对玛尼吐组火山岩进行了同位素年代学分析,并利用全岩成分探讨其形成的大地构造环境。玛尼吐组采集的3个安山岩和粗安岩的锆石U–Pb(LA–ICP–MS)测年结果分别为(142.4±1.4)Ma、(130.0±1.4)Ma和(145.0±1.5)Ma,显示该地区玛尼吐组形成于早白垩世。样品SiO2含量为59.43%~64.73%,Al_(2)O_(3)含量为15.66%~17.19%,K_(2)O含量为2.56%~5.03%,Na_(2)O含量为3.59%~4.53%,全碱含量为6.36%~9.56%;微量元素以富集大离子亲石元素和LREE,亏损Nb、Sr、P和Ti为特征;稀土元素ΣREE=118.71×10^(–6)~189.99×10^(–6),轻重稀土分馏系数(La/Yb)N为8.88~9.58,δEu值为0.66~0.95,Eu负异常,与岛弧火山岩地球化学特征相似。对比大兴安岭西部玛尼吐组西部、中部(~140 Ma)和东部火山岩年龄,笔者认为其玛尼图组火山岩类最老形成于晚侏罗世(~158 Ma),向东逐渐变新为早白垩世(140~130 Ma),这一变化与蒙古–鄂霍次克洋自西向东的闭合及陆块的后碰撞伸展有关。

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CO_(2)、SO_(2)和CH_(4)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。