Revision of the Conchostracan Genus Tenuestheria from the Upper Cretaceous Lanxi Formation in Zhejiang and Its Biostratigraphic Significance in Southeast China

The diagnosis of the conchostracan genus Tenuestheria from the Lanxi Formation in Jinhua, Zhejiang Province in Southeast China is revised following an examination of the type species under a scanning electron microscope, which revealed some morphological features on the carapace that had not been recognized previously. The importance of the Tenuestheria Fauna is considered in the context of correlation of six Turonian–Santonian formations in this region of China. The value of the Cenomanian Nemestheria and Turonian Linhaiella faunas in correlating the underlying early Late Cretaceous formations is also noted.     

Campanian Climatic Change: Isotopic Evidence from Far East, North America, North Atlantic and Western Europe

Paleoclimatic settings have been reconstructed for the Campanian using original oxygen-isotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes (95, 98, 102, 390A, and 392A) in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum-Pacific (to 24.2°C) and the eastern circum-Pacific (to 26.4°C) areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland (22.4–25.5°C), which agrees with the data on the Campanian Barykovskaya flora in high latitudes (Golovneva and Herman, 1998) and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska (19.4°C) and the Koryak Upland (22.4–25.5°C), we also expect Latest Campanian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main climatic tendency during the Campanian (with the exception of Latest Campanian) has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido-South Sakhalin (Krilyon) marine basin. In contrary to Huber’s et al. (2002) assumption, we expect warm greenhouse conditions during the most part of the Campanian.     

松山-布容地磁极性倒转在黄土高原东南缘记录的可靠性探讨

中国黄土的剩磁获得机理和Lock-in深度问题是目前黄土古地磁研究的焦点和核心问题之一,它直接关系到黄土时间标尺的精确度和海陆古气候对比的可靠性。文章以黄土高原东南缘三门峡曹村剖面获得的高分辨率古地磁极性界线作为年代控制点,通过黄土-古土壤序列1.1Ma以来的磁气候记录与近年来中、高纬度大西洋ODP/DSDP钻孔中获得的具有高分辨率古地磁年代约束的深海氧同位素记录进行了详细对比分析,提出与传统的海陆对比不同的基于古地磁界线的海陆对比方案:松山/布容地磁极性转换界线记录在曹村剖面S8的顶部,可对应深海沉积的MIS19,而不是前人认为的MIS21。黄土高原不同地区记录东亚冬、夏季风的差异性和变化性可能是全球具同时性的松山/布容地磁极性转换在黄土高原不同地区产出层位不一致性的主要原因,而基于Lock-in模型的天文年代标尺则可能高估了黄土/古土壤的年龄。     

SHRIMP U-Pb Zircon Age of the Ka''''erjiao Intrusion in the Sawur Region in West Junggar,Xinjiang

Acid intrusions are widespread in the Sawur region, Xinjiang. The Ka'erjiao intrusion is mainly composed of albite granite porphyry, K-feldspar granite porphyry, ivernite and granite porphyry. Being a transitional product between magma intrusion and eruption in the Sawur region, the Ka'erjiao intrusion was formed at the telophase of the late Carboniferous to the begining of early Permian as determined by the SHRIMP U-Pb zircon dating, with an age of 302.6±7.6 Ma (1σ). The intrusion consists of alkali-enriched rock, whose REE distribution patterns are of the LREE enrichment type, theδEu value is low and Nd, Sr, Pb isotopes reflect its mantle source characteristics. Theδ18O value of intrusion is low as a result of isotope exchange with meteoric water. The geochemical characteristics show that it was formed in a post-collisional tectonic setting. Taking combined considerations of current studies of A-type granites and Permian volcanic rocks, we think that in the telophase of the late Carboniferous to the beginning of the early Permian, the Sawur region was within the extension or compressional to extensional period of a post-collisional stage. The Ka'erjiao intrusion from mantle sources can confirm the vertical continental crust growth in the late Paleozoic. The Sawur region in west Junggar is consistent with east Junggar in post-collisional tectonic evolution process.     

Provenance of Precambrian Fe- and Al-rich Metapelites in the Yenisey Ridge and Kuznetsk Alatau, Siberia： Geochemical Signatures

Major, trace and rare earth element contents of Fe- and Al-rich metapelites from the Korda （Yenisey Ridge） and Amar （Kuznetsk Alatau） formations were determined to examine the nature, origin and evolution of their protoliths. Results indicate that these rocks are the redeposited and metamorphosed products of Precambrian kaolinitic weathering crusts, while the geochemical distinctions between the studied metapelites are determined by different weathering conditions in the source area and tectonic settings. The protolith of the Korda Formation metapelites was produced by erosion products of the post-Archean granitoid rocks, which accumulated under humid climate conditions in shallow-water basins along the continental margin. The geochemical characteristics of the deeper primary deposits of the Amar Formation suggest that volcanogenic material of mafic composition derived from an island-arc environment had a major role in supplying the erosion zone. These results agree with lithofacies data and with the geodynamic reconstruction of the evolution of the Yenisey Ridge and Kuznetsk Alatau during the Mesoproterozoic and Neoproterozoic, respectively. It was shown that REEs had limited mobility during contact metamorphism. The coherent mobility of REEs during collisional metamorphism may be attributed both to mineral reactions responsible for modal changes and to local chemical heterogeneity inherited from the initial protolith.     

中亚造山带中的燃烧变质事件及其年代学研究

Combustion metamorphic(pyrometamorphic)complexes produced by prehistoric natural coal fires are widespread inCentral Asia,namely at the interfaces between mountain systems and the flanking sedimentary basins.Large-scale and prolonged firesaccompanied the initial orogenic stages as unweathered coal-bearing formations became exposed into the aeration zone.Pyrometamorphic rocks are comparable to sanidinite facies rocks in formation conditions and in alteration of sedimentary material but,unlike these,their protolith underwent different melting degrees to produce either ferrous basic paralavas or glazed clinkers.The phasecomposition of the newly-formed melted rocks are favorable for~(40)Ar/~(39)Ar dating of combustion metamorphic events which are coeval tothe onset of the main stage of recent orogenic events.We suggest a new algorithm providing correct ~(40)Ar/~(39)Ar dating ofpyrometamorphic rocks followed by well-grounded geological interpretation.We studied pyrometamorphic rocks in the western Salairzone of the Kuznetsk coal basin where combustion metamorphism under temperatures above 1000℃acted upon large volumes of coal-bearing sediments.Samples of paralavas were dated by the step heating ~(40)Ar/~(39)Ar method checked against internal(plateau andisochrone ages)and external("criterions of couple")mineralogical criterions,and against preliminary dating from geological andstratigraphic evidence.As a result,we distinguished two groups of dates for combustion metamorphic events.The first one(1.2±0.4Ma)is drawn towards the west boundary of Prokopyevsk-Kiselevsk block of Salair zone,while the second one(0.2±0.3Ma)isconfined to its east boundary.The former ages represent rocks in the western edge of the Prokopievsk-Kiselevsk block of the Salair zoneand the latter ages correspond to those in its eastern edge.The dates record the time when the fault boundaries of the blocks wererejuvenated during recent activity and the block accreted to the Salair orogenic area as a piedmont step.These are the first absolute agesobtained for the onset of uplift of the northern edge of the Ahai-Sayan area,the key event of its neotectonic history.The suggestedapproach to the choice of objects,classification of rocks,and interpretation of~(40)Ar/~(39)Ar data is universal and can be practiced in anyarea subjected to combustion metamorphism.     

柴达木盆地北缘大柴旦地区古生代花岗岩锆石SHRIMP定年

大柴旦地区是柴北缘古生代超高压带的重要组成部分,与超高压岩石相伴的花岗岩十分发育。这些花岗岩具有两类不同的岩石地球化学特征,Ⅰ类以 Na_2O/K_2O 比值小于1、明显的负 Eu 异常和低 Sr、高 Y 为特征,具有 S-型花岗岩的属性,Ⅱ类以 Na_2O/K_2O 比值大于1、弱负 Eu 异常到正 Eu 异常和高 Sr、低 Y 为特征,具有Ⅰ-型花岗岩的属性,反映了它们的源岩及成因上的差异。锆石 SHRIMP U—Ph 定年结果表明,大柴旦地区花岗岩的年龄可分为三组,第一组年龄为446.3±3.9Ma,第二组年龄分别为408.6±4.4Ma、403.3±3.8Ma、401.8±3Ma,第三组年龄分别为374.5±1.6Ma、372±2.1Ma。结合区域地质特征,我们认为,第一组年龄可能反映了柴达木陆块与中南祁连板块碰撞的时代,第二组年龄可能反映了深俯冲地下的板块由于拆沉而折返的时代,第三组年龄可能反映了碰撞隆起后造山带上不同块体之间的伸展、滑塌的时代。     

天然硝石和其赋存条件

硝石属硝酸盐矿物,在自然界中有钠硝石和钾硝石两种。硝酸盐易溶于水,它是一种强硝酸盐,分布在炎热沙漠地区的现代沉积层中,其中氮来自空气。这种元素的氧化作用主要是由生物作用引起的,也就是与土壤中的细菌作用或大气中放电作用有关。钠硝石,或称智利硝石,其化学成分是NaO     

关于中国岩石绝对年龄的讨论

这个問題的研究是根据中国科学院地貭研究所和中国地貭部地貭研究所的倡議而进行的。参加这項工作的有中苏两国的科学工作者,其中包括中国科学院、苏联科学院、中国地貭部和苏联地貭及保矿部有关研究所的人員。由于有許多人参加这項工作,因而能在1957和1958年夏季收集了必需的岩石标本,并在1958—1959年室内工作期間对它們作了部分的研究。用以鑑定年龄的标本是为了編制中国第一个地貭建造年代簡表和进行华北前寒武系研究而采集的。它们包括了中国主要岩浆旋迴和变貭杂岩体。     

关于估量河流供水量变化的問題

关于河流供水量的多年变化問題,很多研究者都做过研究。而且,由于沒有估量年徑流量变化的成因分析方法,而几乎迫使所有研究者不得不应用概率理論来解决这一問題。但是这个理論只可能估算徑流量变化范圍及不同数值的流量出现的概率,而并沒有提供定出被研究现象在年序中的情况的可能性。为了对于河流年徑流量变化的特点,这种变化按年代次序演变的情况以及几条河流供水量变化过程同时发生的情况等等問題,获得比較明确的概念,到目