辽西早白垩世义县组火山岩的地质特征及其构造背景

早白垩世义县组火山岩虽辽西地区分布最为广泛的中代火山岩。岩石学、元素－同位素地球化学研究表明，义县组火山岩主要为高钾钙碱性系列，相容元素（Cr,Co,Ni,V等）和大离子亲石元素（如Rb,Sr,Ba等）相对富集，市场强元素（如Nb,Ta,Ti,Zr,Hf等）和放射性元素（U,Th）相对亏损，轻重稀土元素分 馏明显，δEu弱负异常，放射成因的Nd,Sr,Pb同位素较低， 具有板内和活动大陆边缘弧地球化学特点。作者认为辽西早白垩世义县组火山岩起源于富集的岩石圈地幔的部分熔融。岩浆在演化过程中以结晶分异作用为主，伴有少量的地壳混染作用，即AFC过程。结合区域构造，作者认为义县组火山岩形成于板内岩石圈的不均匀拉伸环境，是燕山板内造山作用的产物，与中生代古太平洋板块向欧亚板块俯冲没有直接关系。     

冀北张家口组、义县组火山岩SHRIMP定年兼论中国东部大兴安岭兴安岭群和东南沿海火山岩地层时代

冀北张家口组和义县组火山岩锆石 U-Pb定年结果表明 ,张家口组的时代为 1 3 5～ 1 3 0 Ma,义县组的时代为 1 2 9～ 1 2 0 Ma,均属早白垩世。揭示出冀北—辽西地区早白垩世火山沉积盆地的形成和火山活动的时代均具由西向东变新的特征 ,即滦平盆地火山活动始于 1 3 5Ma,承德盆地骆驼山一带始于 1 3 0 Ma,辽西始于 1 2 8Ma。根据年代地层和生物地层资料的对比表明 ,组成中国东部大兴安岭火山岩带的兴安岭群时代主体为早白垩世早—中期 ,组成东南沿海火山岩带的建德群和石帽山群及其相当地层的时代为早白垩世中—晚期 ,因此热河生物群和建德…     

辽西早白垩世义县组燕子沟辽角龙(Liaoceratops yanzigouensis)新材料

报道了一件产自辽西北票地区早白垩世义县组陆家屯层中的燕子沟辽角龙(Liaoceratops yanzigouensis)化石标本。该标本保存了燕子沟辽角龙的一些典型特征:前颌齿3颗;较大的三角形的眶前窝,外颧骨不发育;前齿骨上翘呈钩状;下颌后腹缘的边棱脊发育,并在其后部发育瘤状结节。根据对化石的CT扫描和三维图像重建,笔者对燕子沟辽角龙吻骨的形态特征进行了补充,包括吻骨前缘呈龙骨脊状,后侧发育一棱柱状纵脊等。此外,首次对燕子沟辽角龙的头后骨骼进行了描述,其中,股骨第四转子的特征可能对基干新角龙类的分类有一定意义。     

中国辽西早白垩世义县组一新的美颌龙类

报道了美颌龙类一新属新种:季氏北票颌龙(Beipiaognathus jiigen. et sp. nov.)。它不仅具有美颌龙科的鉴定特征,如扇形的背椎神经脊和强壮的第一指第一指节,而且具有不同于其他美颌龙类的独具特征:不具有小锯齿的锥形牙齿,较长的尺骨,长而强壮的第二指第一指节,以及较短的尾部。这一发现进一步揭示了美颌龙类具有相当高的分异度,为了解美颌龙类的解剖学特征提供了重要信息     

辽西义县组蝾螈类化石新发现

在辽西葫芦岛市附近的早白垩世义县组地层中发现1处新的蝾螈化石点。新台门一带出露的湖相沉积地层主要是一套灰绿色安山岩与紫色泥质粉沙岩的互层。该层中除了产蝾螈化石外,还有诸如Ephemeropsis,Eosestheria,Liaoningocladus等其他动植物化石。过去发现的Liaoxitriton化石点是在同一地区比新化石层稍高的层位中发现的。该类蝾螈化石曾报道产于早白垩世的九佛堂组,但是新近的野外调查表明,该化石点所在层位也属义县组。     

辽西建昌盆地下白垩统义县组的划分及其介形类化石

以要路沟上平房-青石岩、上白庙-罗家沟和小郎家沟-三门店剖面为代表的建昌盆地义县组,自下而上分为5段：第一段主要为砂砾岩（要路沟层）;第二段为砂泥岩、页岩夹凝灰岩,其中包括上白庙层含Cypridea（C.）biventricostata-Yumenia luojiagouensis介形类亚组合带,罗家沟层产介形类Cypridea（C.）luanpingensis-Yumenia unidorsalta-Djungarica camarata亚组合带以及爬行类和鸟类等多门类化石,后狮沟里层以鱼类和介甲类化石为主;第三段岩性是中酸熔岩及其火山碎屑岩;第四段亦称前狮子沟层,以砂页岩为主,夹安山岩,含介形类Yumenia luojiagouensis-Jianchangella dorsicostata亚组合带;第五段为酸性火山岩.上述各层介形类亚组合统归该盆地义县组Cypridea（C.）biventricostata-Yumenia luojiagouensis-Djungarica camarata组合带,其时代属早白垩世早期.文中描述了介形类化石1新属7新种.     

辽西北票—义县地区义县组顶部层位的年龄及其意义

辽西义县组顶部层位为义县组金刚山层之上的黄花山角砾岩层或流纹岩(二者为同时异相).通过对该流纹岩样品中锆石的LA-ICP-MS的U-Pb测年,获得其加权平均年龄为(118.9±1.4)Ma～(119.8±1.9)Ma.通过Ar-Ar方法测年,测得了黄花山角砾岩层的下部岩石中灌入的英安斑岩的年龄,其坪年龄为(122.1±0.3)Ma,等时线年龄为(121.8±1.4)Ma.反映义县组顶部层位的形成时期应在122～119Ma.义县组顶部层位年龄的确定,不仅确定了义县组中热河动物群顶部层位(金刚山层)的上限年龄(约122Ma),同时也确定了义县组火山岩形成的上限年龄(118.9±1.4)Ma～(119.8±1.9)Ma.该地区义县组顶部层位的年龄,也是辽西乃至中国东北地区白垩纪大规模岩浆活动结束的年龄.     

义县组时代及解体

辽西中生界义县组时代归属问题,争论已久,归纳起来主要有三种划分方案：第一,隶属于侏罗纪;第二,隶属于白垩纪;第三,归属于为侏罗－白垩纪,属跨纪地层。结合多年来各科研院所及生产单位采集的众多同位素年龄资料的分析及野外所见接触关系研究认为：原义县组中下部层位岩性组合,根据其特征,需另建立组级岩石单位,应归属到上侏罗统,广义义县组上部层位一套岩性组合,需重新定义,时代应归属到下白垩统。     

中国辽西早白垩世义县组始无齿翼龙新材料

根据新材料,对始无齿翼龙的特征进行了修订：中部颈椎体没有神经棘;肱骨三角嵴的长度与肱骨长度之比率约为0．2．5：翼掌骨的长度与第二翼指骨的长度几乎相等;第二翼指骨与第一翼指骨的长度之比率约为0．76。始无齿翼龙的新标本与正型稍微不同,可能由个体发育所引起。     

辽宁西部兴城曹庄地区义县组岩石地层序列及锆石U-Pb年龄

辽宁西部兴城曹庄地区属于"中生代锦西—锦州—义县—阜新火山喷发带",晚中生代地处阜新—义县盆地的西南端。通过实测剖面和大比例尺调查,确认曹庄地区中生代以火山岩为主的地层可划归义县组,并进一步将其划分为3个岩性段:下段(K_1y~1)由砂砾岩和中性-中基性火山岩组成,中段(K_1y~2)由湖相沉积岩和中性火山岩组成,上段(K1y3)由中性、偏碱性火山岩组成。对尖山剖面火山岩和火山碎屑岩中的锆石采用LA-ICP-MS方法进行的U-Pb测年表明,剖面上义县组下段和中段的年龄分别为131.5±1.4 Ma和129.2±1.0 Ma,次火山状侵位于下段的粗面安山岩加权平均年龄为126.0±1.2 Ma,该结果与北部阜新—义县盆地义县组标准剖面年龄一致。依据火山-沉积序列对比关系,曹庄地区的义县组可以与标准剖面的中、下部对比,但缺失可与标准剖面义县组上部对比的层位,显示该时期火山喷发中心更靠近阜新—义县盆地。     

A New Troodontid (Theropoda: Troodontidae) from the Lower Cretaceous Yixian Formation of Western Liaoning, China

A specimen collected from the Lower Cretaceous Yixian Formation of western Liaoning, China, represents a new genus and species of troodontid theropod. The new taxon is named and described on the basis of the holotype and the only known specimen, which comprises an articulated skeleton with the presacral vertebral, shoulder girdle and forelimbs missing as preserved. Diagnostic features of the new species include nasals that are sinusoid in lateral view, absence of a passage connecting the antorbital and maxillary fenestrae, relatively large teeth, plate-like chevrons forming a band along most of the length of the tail, and a long neck between the femoral head and shaft. The temporal constraints of the three paravian groups (Troodontidae, Dromaeosauridae and Aves) combined with the character distributions among the earliest known troodontids indicate a rapid evolution at the base of the Troodontidae.     

辽西凌源地区义县组下部层位的U—Pb测年及意义

辽西凌源地区义县组的下部层位为大王杖子层，通过对该层位及相关层位样品中锆石的LA—ICP—MS的U—Pb测年，获得大王杖子层的形成年代为125～122Ma。经过综合分析，得出以下初步结论：①辽西凌源地区与北票-义县地区的义县组底界是不等时的；凌源地区义县组下部层位在时代上相当于北票-义县地区的义县组尖山沟层（砖城子层）；②凌源地区的张家口组与义县组之间有约5～6Ma的时间间隔。这不仅验证了凌源地区张家口组与义县组之间为角度不整合接触的可靠性，也暗示该5～6Ma的间隔期为冀北-辽西地区中生代构造格架转换的关键时期；该时期也是我国东北地区中生代岩浆作用的鼎盛时期；同时在冀北-辽西地区，该间隔期之后发生了热河动物群的大爆发，说明该间隔期也是一个重要的生物界限。     

A New Troodontid Dinosaur from the Lower Cretaceous Yixian Formation of Liaoning Province, China

A new troodontid dinosaur,Daliansaurus liaoningensis gen.et sp.nov.,is erected based on a nearly complete specimen from the Lower Cretaceous Yixian Formation of Beipiao City,Liaoning Province,China.This well preserved skeleton provides important new details of the anatomy for Liaoning troodontids,and gives new insight into their phylogenetic relationships and evolution.Daliansaurus is distinguished from other troodontids by an enlarged ungual on pedal digit IV,which is approximately the same size as the sickle-shaped second ungual,and is differentiated from other Liaoning troodontids by a number of characters of the skull,manus,pelvis,and hindlimb.A phylogenetic analysis recovers Daliansaurus within a subclade of Liaoning troodontids that also includes Sinovenator,Sinusonasus,and Mei.We erect a name for this group—Sinovenatorinae—and argue that it reflects a localized radiation of small-bodied troodontids in the Early Cretaceous of eastern Asia,similar to previously recognized radiations of Liaoning dromaeosaurids and avialans.As more Liaoning theropods are discovered,it is becoming apparent that small,feathered paravians were particularly diverse during the Early Cretaceous,and future work is needed to clarify how this diversity arose,which species coexisted,and how these numerous species partitioned niches.     

A Possible Long-tailed Bird with a Pygostyle from the Late Mesozoic Yixian Formation, Western Liaoning, China

AbstractAn incomplete caudal vertebral series (IVPP Vl1309) from the Yixian Formation of late MesozoicJianshangou area of Beipiao, western Liaoning Province, may represent a new bird. The tail is composed of at least 12 free caudal vertebrae and the most distal 5 caudal vertebrae co-ossified into a pygostyle. The pygostyle is plate-like and slightly curved dorsally. The anterior free caudals are amphiplatyan. The anterior caudal surfaces of the last three free caudals are concave, but their posterior articular surfaces are convex. The pygostyle is regarded as the first appeared flight apparatus during the evolutionary process from Archaeopteryx to neornithes. The pygostyle appeared in most early fossil birds and almost all the modem birds. Although their morphologies are different, they are basically formed by at least four last caudal vertebrae. The specimen V11309 is regarded as a bird rather than a non-avian theropod dinosaur based on the following characters: short caudal vertebrae, numerous pits present on the surfaces of the centra and, a foramen present between the basal part of the fused neural spines, which is similar to that of Struthio camelus. The discoveries of pygostyles from the therizinosauroids and oviraptorosaurs may provide strong evidence for supporting the origin of birds from small theropod dinosaurs. The structure of the pygostyle in specimen Vl1309 is different from those of Beipiaosaurus (Therizinosauroid) and Nomingia (oviraptorosaur). The most parsimonious interpretation is that these pygostyle-like structures are independently acquired by Beipiaosaurus and Nomingia during their evolutionary process.     

Largest Toothed Pterosaur Skull from the Early Cretaceous Yixian Formation of Western Liaoning,China, with Comments on the Family Boreopteridae

A new pterosaur Moganopterus zhuiana gen. et sp. nov. is erected based on a complete skull with lower jaws and anterior cervical vertebrae. It is characterized by much elongated upper and lower jaws with at least 62 total, long, curved teeth with sharp tips, a well developed parietal crest extending posterodorsally, forming an angle of 15 degrees with the ventral margin of the skull, the ratio of length to width of cervical vertebrae greater than 5:1. The skull length is 750 mm, and it is the largest toothed pterosaur found so far in the world. Based on this new pterosaur, the Boreopteridae can be divided into two subgroups: Boreopterinae sub-fam. nov. and Moganopterinae sub-fam. nov., which is also confirmed by the phylogenetic analysis.     

辽宁西部义县组湖相枕状熔岩的发现及其意义

通过详细的区调工作,在四合屯、三百垄等地发现了一系列湖相枕状熔岩.研究表明,这些枕状熔岩产于同一地层层位--义县组二段,是珍稀化石沉积层中的火山岩夹层.它们除了代表一次灾变事件外,还反映出形成枕状熔岩的古湖泊接近最大湖泛期,并且水体较深.在这种环境下,生物快速繁衍.而强烈的火山作用使得大批生物死亡,形成了现今丰富的化石组合. 这些枕状熔岩的发现对于准确确定珍稀动植物化石的形成时代和环境具有重要意义.     

On the Lower Cretaceous in Yixian County of Jinzhou City, Western Liaoning, China

Traditionally, the lacustrine deposits in Yixian County of Western Liaoning have been assigned to either “the Dakangpu Bed” of the Yixian Formation or the Jiufotang Formation. However, a 206Pb/238U age of 126.47±0.87 Ma is newly obtained from the tuff sample (06051) of the lacustrine deposits in the Baitaigou fossil site of Potaizi village, Yixian County, indicating that the lacustrine deposits in Potaizi area are approximately equivalent to the Wumingshan volcanics of the Sihetun Bed of the Yixian Formation in Beipiao. From our new dating data have arisen some new problems: Where could we find the Jiufotang Formation in Yixian County? How widely distributed is the Jiufotang Formation in Western Liaoning? Could the traditionally named Jiufotang Formation somewhere in Western Liaoning be the synchronous deposits of other litho-units (e.g. the Yixian Formation) in different facies? Could some lacustrine deposits somewhere in Western Liaoning have been assigned to the Jiufotang Formation?     

辽西北票地区义县组古气候环境标志及其意义

野外地质调查及综合研究表明,包含中华龙鸟、被子植物等珍稀化石的热河生物群的主要赋存层位为义县组二段湖相沉积岩层。对产于不同地点沉积层中的植物、孢粉化石以及木化石进行了总结研究,分析了它们所反映的古气候环境,认为义县组沉积时期存在大量的喜温湿植物,总体指示温暖湿润的生存环境。同时,一些旱生的买麻藤类植物的普遍存在、本内苏铁类的膜质叶以及松柏类的鳞状叶等的特征反映了存在季节性干旱、半干旱气候的可能性。这种气候状况的出现可能与火山活动有关。     

辽西建平马场义县组火山岩LA-ICP-MS锆石U-Pb年龄及其地质意义

辽西建平马场地区出露大量的义县组火山岩,通过对其剖面测制研究发现,义县组火山岩可分为早、中、晚三期。对不同时期火山岩样品进行锆石LA-ICP-MS U-Pb 测年,获得本区义县组早期火山岩形成年龄为(127.7±1.8)~(124.3±1.8)Ma,中期火山岩形成年龄为(122.3±1.4)~(121.8±1.3)Ma,晚期火山岩形成年龄为(114.9±1.8)Ma,时代均为早白垩世。通过与义县-北票、阜新-彰武、凌源-建昌地区的义县组对比得知,本区火山岩开始活动较晚,属于义县组活动的中-晚期;其年代学特征显示辽西各个地区义县组顶、底界是不等时的,是形成于太平洋板块向欧亚大陆俯冲后的伸展环境中。