湖南衡阳盆地东缘白垩系风成沉积的发现及其古环境意义

首次报道了湘中南衡阳盆地东缘上白垩统红花套组中的风成沉积,重新认识了该地区晚白垩世时期的古地理环境。研究区红花套组主要出露一套紫红色块状中-细粒长石石英砂岩、岩屑石英砂岩,普遍见指示风成沙漠环境的巨型板状、楔状交错层理、双向交错层理、平行层理以及典型的风棱石;镜下不含泥质、云母等悬移组分,电镜下可见碟形坑、新月形撞击坑、上翻（平坦）节理片等,综合分析后确认该套砂岩为风成沉积。该套风成砂岩具有重要的古环境意义:风成砂岩的发现,指示该时期为干热气候,沙漠化、盐湖化明显,食物的短缺可能导致衡阳盆地一带恐龙的迁徙;依据沙丘前积纹层倾向特征,恢复了湘中南乃至湖南地区的地表风带特征,为佐证衡阳盆地与其周缘红盆相连通提供一种新的依据。该发现为湖南省的风成沉积领域提供了宝贵的研究材料。     

Tetrapods from the Upper Cretaceous (Turonian–Maastrichtian) Bauru Group of Brazil: a reappraisal

An updated, annotated list of all tetrapods from the Adamantina, Uberaba and Marília formations (Bauru Group), which constitute some of the best studied Upper Cretaceous units in Brazil, is presented. Tetrapod diversity in the Bauru Group is remarkable, including an admixture of typically austral Gondwanan taxa (e.g., abelisaurids, notosuchians) and boreal Gondwanan forms (e.g., carcharodontosaurids). Of note is the absence of Laurasian taxa in the upper portion of the Bauru Group. With the exception of some turtles, an anuran, mesoeucrocodylians and one titanosaur, most taxa from the Bauru Group are based on fragmentary and isolated bones, and as such many specimens can be identified only to a higher taxonomic level. Fishes, turtles, anurans, mesoeucrocodylians, dinosaurs, birds and mammals from the Adamantina and Marília formations resemble the latest Late Cretaceous vertebrate faunas from southern South America, except for the absence of ornithischian dinosaurs.     

Aeolian sand sea development along the mid‐Cretaceous western Tethyan margin (Spain): erg sedimentology and palaeoclimate implications

The existence of a mid‐Cretaceous erg system along the western Tethyan margin (Iberian Basin, Spain) was recently demonstrated based on the occurrence of wind‐blown desert sands in coeval shallow marine deposits. Here, the first direct evidence of this mid‐Cretaceous erg in Europe is presented and the palaeoclimate and palaeoceanographic implications are discussed. The aeolian sand sea extended over an area of 4600 km². Compound crescentic dunes, linear draa and complex aeolian dunes, sand sheets, wet, dry and evaporitic interdunes, sabkha deposits and coeval extradune lagoonal deposits form the main architectural elements of this desert system that was located in a sub‐tropical arid belt along the western Tethyan margin. Sub‐critically climbing translatent strata, grain flow and grain fall deposits, pin‐stripe lamination, lee side dune wind ripples, soft‐sediment deformations, vertebrate tracks, biogenic traces, tubes and wood fragments are some of the small‐scale structures and components observed in the aeolian dune sandstones. At the boundary between the aeolian sand sea and the marine realm, intertonguing of aeolian deposits and marine facies occurs. Massive sandstone units were laid down by mass flow events that reworked aeolian dune sands during flooding events. The cyclic occurrence of soft sediment deformation is ascribed to intermittent (marine) flooding of aeolian dunes and associated rise in the water table. The aeolian erg system developed in an active extensional tectonic setting that favoured its preservation. Because of the close proximity of the marine realm, the water table was high and contributed to the preservation of the aeolian facies. A sand‐drift surface marks the onset of aeolian dune construction and accumulation, whereby aeolian deposits cover an earlier succession of coastal coal deposits formed in a more humid period. A prominent aeolian super‐surface forms an angular unconformity that divides the aeolian succession into two erg sequences. This super‐surface formed in response to a major tectonic reactivation in the basin, and also marks the change in style of aeolian sedimentation from compound climbing crescentic dunes to aeolian draas. The location of the mid‐Cretaceous palaeoerg fits well to both the global distribution of other known Cretaceous erg systems and with current palaeoclimate data that suggest a global cooling period and a sea‐level lowstand during early mid‐Cretaceous times. The occurrence of a sub‐tropical coastal erg in the mid‐Cretaceous of Spain correlates with the exposure of carbonate platforms on the Arabian platform during much of the Late Aptian to Middle Albian, and is related to this eustatic sea‐level lowstand.     

Preservation of aeolian genetic units by lava flows in the Lower Cretaceous of the Paraná Basin, southern Brazil

The Lower Cretaceous geological record of the intracratonic Paraná Basin in southern Brazil comprises a thick succession of aeolian sandstones and volcanic rocks. The intercalation between aeolian sandstone and volcanic floods allowed the preservation of distinct aeolian genetic units. Each genetic unit represents an accumulation episode, bounded by supersurfaces, that coincides with the base of lava flood events. The entire package can be subdivided into a Lower Genetic Unit, which corresponds to aeolian sandstones preserved below the initial lava flows (Botucatu Formation), and an upper set of genetic units, which comprises interlayered aeolian deposits and lava floods (Serra Geral Formation). The Lower Genetic Unit is up to 100 m thick. Its base is composed of ephemeral stream and aeolian sand sheet deposits that are overlain by cross‐bedded sandstones whose origin is ascribed to simple, locally composite, crescentic and complex linear aeolian dunes. Aeolian accumulation of the lower unit was possible as a result of the existence of a wide topographic basin, which caused wind deceleration, and a large sand availability that promoted a positive net sediment flux. The Upper Genetic Units comprise isolated sand bodies that occur in two different styles: (1) thin lenses (<3 m thick) formed by aeolian sand sheets; and (2) thick sand lenses (3–15 m) comprising cross‐bedded cosets generated by migration and climbing of simple to locally composite crescentic aeolian dunes. Accumulation of the aeolian strata was associated with wind deceleration within depressions on the irregular upper surface of the lava floods. The interruption of sedimentation in the Lower and Upper Genetic Units, and related development of supersurfaces, occurred as a result of widespread effusions of basaltic lava. Preservation of both wind‐rippled topset deposits of the aeolian dunes and pahoehoe lava imprints indicates that lava floods covered active aeolian dunes and, hence, protected the aeolian deposits from erosion, thus preserving the genetic units.     

四川盆地白垩纪沙漠石英沙颗粒表面特征

石英具有较大的硬度和较高的化学稳定性，因而其颗粒表面特征能很好地反映沉积环境。而通过扫描电镜研究石英颗粒表面微细特征是分析沉积环境行之有效的方法。虽然多数人认为四川盆地白垩纪地层存在沙漠沉积(打儿凼组和夹关组)，但仍有人对沙漠沉积的存在持怀疑态度，并认为是河流成三角洲沉积。过去关于其沉积环境的判别主要是根据沉积结构和构造，并未对其石英沙颗粒表面特征进行过系统分析。笔者对采自四川盆地白垩系不同层位地层的样品进行了石英沙颗粒表面特征系统分析。结果表明，石英沙颗粒表面特征分析可以成功地将石英沙区分为风成和水成沉积。因此，本文从石英沙颗粒表面特征方面进一步肯定了四川盆地白垩纪古沙漠的存在。     

Adsorption of copper(II) from aqueous solution by Beidellite

Dry lakes, degraded sandy grasslands, abandoned farmland and mobile dunes which are widely distributed throughout the arid areas of northern China have been investigated in this work. Gain-size distribution of the surface sediments of Manas lake in Junggar basin, Juyan lake in the Alxa plateau, Zhuye lake in Minqin basin and most deserts (such as Mu Us desert, Otindag desert, Horqin desert and Hulun Buir desert) in China have been analyzed. The results show clay with particle sized <10 μm on the surface sediments of dry lakebed and sandy grassland developed from dry lakebed, respectively, account for >60% and ∼50% of the total mass. Since the tiny particles on the surface of abandoned farmland are blown away easily and rapidly, the content of clay particles in Minqin basin is <14%. The grain-size distribution of mobile dunes in northern China mainly consists of particles >63 μm and few particles <10 μm. Consequently, although sand/dust storms originate primarily in the western deserts, the gobi areas of the Alxa plateau, the north and east of Hexi Corridor and in central Mongolia, the widely distributed dry lakebeds, sandy grasslands and abandoned farmland adjacent to the deserts also contribute to aeolian dusts. Hence, the material sources for sand dust storm in East Asia include inland deserts, but also dry lakes, sandy grasslands and abandoned farmland, which are widely distributed throughout the arid inlands of northern China.     

Desert sand plain and sabkha deposits from the Bunter Sandstone Formation (L. Triassic) at the northern margin of the German Basin

Facies studies of well cores from the Bunter Sandstone Formation in the Tønder area, Denmark indicate, that the formation is composed of two desert sand plain sequences associated with sabkha and inland basin (lake?) mudstones. The lower desert sand plain sequence consists of subaerial sand flat deposits overlain by aeolian sand sheet and dune facies topped by interbedded aeolian and ephemeral river deposits. The upper desert sand plain sequence consists of ephemeral river deposits partly interbedded with and overlain by sabkha and inland basin mudstones. Two shoreline sandstones occur in the uppermost part. Both sequences are interpreted mainly in terms of tectonic subsidence of the basin and related upheavals of the source regions. The lower sequence represents a rather continuous progradation of the desert sand plain followed by a rapid transgression of the waters from the inland basin. The upper sequence represents brief periods of fluvial progradation followed by a gradual retreat of the river plain. The most distal part of the sand plain was finally reworked by weak wave-action.     

汝阳盆地早白垩世恐龙蛋壳的发现及其意义

汝阳盆地是豫西地区的一个中—新生代断陷盆地,自2006年以来发现了一个以巨型蜥脚类恐龙为代表的恐龙动物群。本文描述了近期发现于汝阳盆地下白垩统郝岭组中的若干恐龙蛋蛋壳碎片。基于以下对蛋壳宏观形态和显微特征的分析,这些蛋壳碎片可以归入长形蛋科(Elongatoolithidae)的长形蛋属(Elongatoolithus):蛋壳外表面具分散瘤点状或线性脊状的纹饰;蛋壳自内而外分为锥体层和柱状层,二层之间的界线不清晰;锥体层中锥体排列紧密;柱状层中具波浪状的平行生长纹。这一发现代表了长形蛋属在早白垩世地层中的首次记录,进一步拓展了该蛋属的地史和古地理分布。由以往已知的化石关联推测,这些蛋壳可能与该层位中的窃蛋龙类如刘店洛阳龙(Luoyanggia liudianensis)等具有相关性,表明汝阳盆地在早白垩世晚期具有适宜该类恐龙生存与繁殖的环境。     

Dinosaur- and mammal-bearing aeolian and associated deposits of the Upper Cretaceous in the Gobi Desert (Mongolia)

The Barun Goyot Formation (? Campanian-Maastrichtian) consists of continental red-bed type sandstones. The formation was interpreted in terms of intertonguing and/or alternating dune deposits and sediments of intermittent lakes and streams. The mega cross-stratified sandstone units which show considerable lateral continuity and little variation of foresets dip were described as buried transverse dunes. They are rather poor in animal fossils. Most dinosaurs and mammals occur in water-deposited interdune sediments. This is due to ecological differences between bare dunes and the interdune depression which had a vegetation cover.     

白垩纪四足动物足印的生物地层学、生物年代学与遗迹相

从全球范围来看,白垩纪四足动物的足印多数是非鸟恐龙与鸟类留下的痕迹;少量足印来自翼龙、鳄鱼、龟、哺乳动物和其他四足动物。白垩纪的足迹化石以东亚(尤其是中国和朝鲜)和北美西部的最为人所知。南美(主要是阿根廷和巴西)也有一定数量广泛分布的足迹化石,欧洲、非洲与澳大利亚的白垩纪足迹组合则鲜为人知。以白垩纪四足动物的足印记录为基础,我们对两个全球足印生物年代重新进行了检查。早白垩世生物年代以蜥脚类与鸟脚类的足迹为特征。晚白垩世生物年代中的蜥脚类足迹较少,但是鸭嘴龙、暴龙和角龙的足迹增多了。另外,白垩纪足印化石的记录中记载了许多重要的生物地层学信息,如北美白垩纪中期蜥脚类恐龙的消失,以及白垩纪末恐龙的绝灭。越来越多来自东亚的白垩纪足印记录使我们对更精细的地方性白垩纪足印生物年代学有了初步印象。因此,以地方性四足恐龙(包括鸟类)遗迹属的地层分布为基础,可以识别出三个或四个足印生物年代。种类丰富并具有地方性特色的东亚的白垩纪鸟类动物的遗迹群,可能指示白垩纪时东亚存在着一个独特而繁盛的鸟类动物群。以足印化石为基础的这一假说有待进一步的验证。     

新构造运动在塔里木盆地演化中作用

在第四纪以来的新构造运动的影响下,塔里木盆地逐渐向封闭的干旱盆地演化。由于波动式的新构造运动在每阶段表现的形式有差异,因而盆地的演化也相应表现出明显的阶段性。该盆地新构造运动大致经历了上新世末—早更新世、早更新世末—中更新世以及晚更新世三个阶段,其中以早更新世末的一次构造运动对盆地的地貌影响最大。新构造运动是由印度板块和欧亚板块挤压引起的,故塔里木盆地与青藏高原的演化阶段在时间上大致吻合。     

西秦岭北缘武山地区上白垩统沙漠相沉积特征

西秦岭广泛但不连续分布着一套晚白垩世红层地层。这套红层地层所代表的原型沉积盆地是西秦岭中生代陆内造山期发育的相互孤立的山间盆地拟或是整体统一红层盆地新生代以来地壳隆升侵蚀破坏的残留一直存在争议。这个争议问题即关乎到对西秦岭中生代末期的构造地貌状态的认识,也关乎到现今青藏高原东北缘新生代以来地壳隆升初始地质背景。通过对西秦岭北缘武山地区上白垩统红层沉积地层中发育的一套砖红色砂岩的沉积序列、沉积构造、粒度分布等宏观地质特征的较详细研究,结合对这套砂岩的矿物成分和显微结构以及石英颗粒SEM表面结构特征的研究,表明这套砖红色砂岩具有如下特征:1）发育典型的大型风成交错层理;2）粒度均匀,分选好,以中-细砂、极细砂组分为主,缺乏粉砂-黏土颗粒组分;3）石英颗粒磨圆度好,表面发育碟形和新月形坑、溶蚀坑、硅质薄膜等风成砂颗粒具有的独特表面特征。据此提出这套砖红色砂岩是典型的沙漠相沉积的新认识,并根据沙漠相沉积类型的识别标志将其分为沙丘沉积和丘间沉积两种沉积类型。秦岭北缘武山地区晚白垩世沙漠相沉积的存在,结合西秦岭腹地同时代的哈达铺、岷县西江等地分布在山顶面的晚白垩世红层地层中存在类似的沙漠相沉积分析,提出了西秦岭晚白垩世不仅处于干旱炎热气候环境,而且曾呈现出地形相对平缓的泛盆地构造地貌状态。这套红层沉积反映了西秦岭晚白垩世为统一红层沉积盆地而非孤立的山间盆地,现今多不连续分布在山顶面之上是新生代以来地壳不均匀隆升和侵蚀共同作用的结果。     

Overabundance of piscivorous dinosaurs (Theropoda: Spinosauridae) in the mid-Cretaceous of North Africa: The Algerian dilemma

The informally called ‘Continental intercalaire’ is a series of continental and brackish deposits that outcrops in several regions of North Africa. The age of the series is not well-constrained, but its upper part, visible in the ‘Kem Kem beds’ in Morocco and in Bahariya in Egypt, is regarded as early Cenomanian in age. Spinosaurid remains are an important component of this series, but records of this dinosaur are surprisingly rare in Algerian localities of the ‘Continental intercalaire’. Here, we describe a vertebrate assemblage from two localities, Kénadsa and Menaguir, situated in the Guir basin, Western Algeria. The assemblage comprises hybodont sharks, sarcopterygian fishes, ray-finned fishes, turtles, crocodiles and dinosaurs. Among the latter, only teeth of theropods have been recovered and 94% belong to Spinosaurus. The assemblage is taxonomically very similar to the Moroccan and Egyptian assemblages mentioned above. This study: 1) suggests a likely early Cenomanian age for the Guir basin deposits containing the assemblage; 2) provides a new evidence of the homogeneity of the early Cenomanian vertebrate fauna throughout North Africa; and 3) confirms the overabundance of theropod dinosaurs, especially spinosaurs, in the assemblage showing a possible shortcut in the vertebrate food chain. The northern most locality, Menaguir, shows sedimentological and ichnological evidence of marine influences indicating that the palaeoenvironment shows spatial heterogeneities.     

Cretaceous sedimentary basins in Sichuan,SW China: Restoration of tectonic and depositional environments

This study documents sediment infill features and their responses to the tectonic evolution of the Sichuan Basin and adjacent areas. The data include a comparison of field outcrops, well drillings, inter-well correlations, seismic data, isopach maps, and the spatial evolution of sedimentary facies. We divided the evolutionary history of the Sichuan Cretaceous Basin into three stages based on the following tectonic subsidence curves: the early Early Cretaceous (145–125 Ma), late Early Cretaceous to early Late Cretaceous (125–89.8 Ma), and late Late Cretaceous (89.8–66 Ma). The basin underwent NW–SE compression with northwestward shortening in the early Early Cretaceous and was dominated by alluvial fans and fluviolacustrine sedimentary systems. The central and northern areas of the Sichuan Basin were rapidly uplifted during the late Early Cretaceous to early Late Cretaceous with southwestward tilting, which resulted in the formation of a depression, exhibited southwestward compression, and was characterized by aeolian desert and fluviolacustrine deposits. The tectonic framework is controlled by the inherited basement structure and the formation of NE mountains, which not only affected the clastic supply of the sedimentary basin but also blocked warm-wet currents from the southeast, which changed the climatic conditions in the late Late Cretaceous. The formation and evolution of Cretaceous sedimentary basins are closely related to synchronous subtle far-field tectonism and changes in climate and drainage systems. According to the analysis of the migration of the Cretaceous sedimentation centers, different basin structures formed during different periods, including periods of peripheral mountain asynchronous thrusting and regional differential uplift. Thus, the Sichuan Cretaceous sedimentary basin is recognized as a superimposed foreland basin.     

华南衡阳盆地上白垩统黄土类似物的初步研究

中国新生代黄土序列具有沉积速率高、连续性好等特点,记录了东亚地区持续的古气候动力学演化和重大地质事件信息。受区域构造-地貌和大气环流格局影响,中生代晚期华南发育了众多盆山型古沙漠系统且出露了巨厚的风成砂,但几乎未有学者提及黄土/黄土类似物的存在。本文通过粒度端元解析、野外露头的构型分析等手段,对衡阳盆地上白垩统红花套组进行了初步研究,识别出风成砂丘、砂席和泥滩等环境类型;并在泥滩环境中提取到黄土类似物的粒度组分信号,同时提出了黄土类似物的风成成因,总结了其形成-堆积过程。这项工作旨在探索白垩纪黄土类似物存在的可能性,为未来开展华南陆块中生代风尘记录研究提供契机。     

黑龙江沿岸晚白垩世恐龙生物群化石产地的初步预测

根据对黑龙江沿岸孙吴、逊克和嘉荫保兴-炮台店一带晚白垩世地层与嘉荫乌拉嘎、龙骨山等含恐龙化石群的渔亮子组(K2y)等对比及在前三个地区已发现部分恐龙化石的线索,初步预测孙吴北部、逊克东南部和嘉荫保兴-炮台店等三地区可能为较大规模的恐龙化石群产地。预测区含恐龙化石的晚白垩世地层均属河流-湖泊相沉积,除恐龙外,尚可能发现叶肢介、介形类、鱼、龟鳖类、鳄、鸟类及被子植物等伴生化石。上述地区下伏于渔亮子组的太平林场组(K2t)和永安村组(K2yn)等地层,也有含恐龙化石的可能性。     

Windblown desert sands in coeval shallow marine deposits: a key for the recognition of coastal ergs in the mid‐Cretaceous Iberian Basin,Spain

Grain size and SEM analyses suggest the presence of Cretaceous windblown desert sands in coeval shallow marine environments. Size distributions and microtexture data allowed us to infer a climate change to more arid conditions in the Iberian Basin during the mid‐Cretaceous. The grain size of the sands in the late Aptian to early Cenomanian shallow‐marine deposits in the western sub‐basins of the Maestrazgo Basin (Teruel, Spain) is almost exclusively in the range between 1.5 and 3 Φ (0.35–0.125 mm), reflecting a prolonged or at least recurrent preselection of aeolian sands. The palaeolatitude of 25°N showed a change from a warm humid climate during the Lower Cretaceous to an arid desert climate in the eastern sector of Iberia during the late Aptian–early Cenomanian. Winds supplied abundant desert sand to the estuarine and deltaic sedimentary environments where it was worked up in sandy sub‐ and intertidal facies with a striking absence of mud in cross‐bedded sets which otherwise clearly reflect the influence of a semi‐diurnal tidal system.     

鄂尔多斯盆地沉积体系与古地理演化

基于多年来对盆地周缘大量的野外露头勘察以及盆地内部分钻井岩心描述,主要从沉积环境、岩石类型、岩石沉积结构及构造、古生物化石等众多方面,对鄂尔多斯盆地的沉积体系类型和特征以及古地理环境的整体演化进行了全面、系统的研究。结果表明,中新元古代长城期至蓟县期,主要由陆相—滨浅海相沉积转变为碳酸盐潮坪沉积。早古生代辛集期至朱砂洞期,主要由盆地西南缘的环古陆砂坪沉积演变为云坪沉积;馒头期至三山子期,主要发育开阔海台地沉积,但范围变化相对较大;冶里期至亮甲山期,主要由盆地东南缘的环古陆泥云坪沉积演变为云坪沉积;马家沟期大规模海侵形成了广阔的浅水陆表海沉积;峰峰期以台地前缘斜坡和大陆斜坡海槽沉积为主;平凉期盆地南部出现了台地边缘浅滩;背锅山期仅在盆地西南角分布开阔台地及台前斜坡沉积。晚古生代—中三叠世本溪期为填平补齐时期,发育潮坪—潟湖—障壁岛—浅海陆棚沉积:太原期,盆地东部浅海陆棚沉积范围减小;山西期至纸坊期,盆地均主要以三角洲沉积和浅湖沉积为主,但各期沉积范围均有变化。晚三叠世延长期—白垩纪,主要为湖泊沉积并伴有曲流河、辫状河以及三角洲等沉积体系:延长期长7油层组沉积时期湖侵范围最大;富县期至安定期,以曲流河、三角洲和浅湖沉积为主,但浅湖沉积范围在不同时期有明显变化,安定期出现深湖沉积;芬芳河期主要为冲积扇沉积。白垩纪盆内沉积范围变小,主要发育沙漠沉积和浅湖沉积。