New Bathonian (Middle Jurassic) ammonite assemblages from Kutch,India

The Bathonian ammonite assemblages have been previously poorly recorded in Kutch. The present study has unearthed a rich array of ammonite taxa ranging from the Middle to Upper Bathonian. While Oxycerites Rollier (1909) is a new record from Kutch, the oldest occurrence of Choffatia Siemiradzki (1898) has been found from the Middle Bathonian horizon. Oxycerites cf. orbis (Giebel) is a zonal index of the Late Bathonian in other areas and thus facilitates interprovincial correlation. Besides, palaeobiogeographic and stratigraphic distribution of many species have been modified based on new information. For example, macrocephalitin species, i.e., Kamptokephalites cf. etheridgei Spath (1928), Macrocephalites bifurcatus transient intermedius Spath (1928), M. cf. mantataranus Boehm (1912) were previously known from West Pacific, Indonesia have been now found in Kutch. Gracilisphinctes Buckman (1920) has been previously known to occur during the Middle Bathonian time, the present work extends its stratigraphic distribution up to the definite Upper Bathonian horizon. Procerites hians (Waagen) an endemic species in Kutch previously known from the Upper Bathonian beds, its stratigraphic range has been extended down to the Middle Bathonian.Detail taxonomy of the newly obtained taxa has been done and in many cases sexual dimorphism has been recognized.     

New Bathonian (Middle Jurassic) ammonite assemblages from Kutch, India

The Bathonian ammonite assemblages have been previously poorly recorded in Kutch. The present study has unearthed a rich array of ammonite taxa ranging from the Middle to Upper Bathonian. While Oxycerites Rollier (1909) is a new record from Kutch, the oldest occurrence of Choffatia Siemiradzki (1898) has been found from the Middle Bathonian horizon. Oxycerites cf. orbis (Giebel) is a zonal index of the Late Bathonian in other areas and thus facilitates interprovincial correlation. Besides, palaeobiogeographic and stratigraphic distribution of many species have been modified based on new information. For example, macrocephalitin species, i.e., Kamptokephalites cf. etheridgei Spath (1928), Macrocephalites bifurcatus transient intermedius Spath (1928), M. cf. mantataranus Boehm (1912) were previously known from West Pacific, Indonesia have been now found in Kutch. Gracilisphinctes Buckman (1920) has been previously known to occur during the Middle Bathonian time, the present work extends its stratigraphic distribution up to the definite Upper Bathonian horizon. Procerites hians (Waagen) an endemic species in Kutch previously known from the Upper Bathonian beds, its stratigraphic range has been extended down to the Middle Bathonian.Detail taxonomy of the newly obtained taxa has been done and in many cases sexual dimorphism has been recognized.     

Multistage evolution of a volcanic suite in the Eastern Mecsek Mountains, Southern Hungary

Summary This paper proposes a magmagenetic model for the Lower Cretaceous volcanic rocksuite from the Eastern Mecsek Mountains in Southern Hungary based on both major and trace element analysis as well as mineralogical investigations.Trace element patterns of these volcanic rocks refer to a parental melt that originated from a re-enriched mantle. Relatively low Cr, Ni, and Mg# even in the least fractionated olivine-clinopyroxene basalts indicate fractionation of olivine and clinopyroxene prior to the ascent ofolivine-clinopyroxene basaltic magmas which is evident by glomeroporphyritic clinoproxenes with forsterite-rich olivines. Subsequent fractionation of some more 35% of the olivine-clinopyroxene basaltic magma resulted in the formation ofplagioclase basaltic magmas which are devoid of olivine. Instead plagioclase and opaques became the dominant crystallizing phases. After about 60% fractionationmugearites formed from the residual melt. These are depleted in Ni and Cr as well as in Fe, Ti, and V indicating the fractionation of additional Fe-Ti oxides.Tephriphonolitic dike-rocks formed by further fractionation totalling 70–80%, with apatite and feldspar as additional fractionating phases. Finally, thephonolites represent 15–20% residuum of the olivine-clinopyroxene basaltic melt which these calculations started with. They are characterized by strong depletion of Ti and V and all compatible elements; Zr/Hf ratios increase due to clinopyroxene and Fe-Ti oxide fractionation, P and middle rare earth elements are depleted due to apatite fractionation, and Sr, Ba, and Eu are depleted due to feldspar fractionation. Incompatible trace elements such as rare earth elements, Zr, Hf, Nb, Ta, and Rb reach maximum concentrations in the phonolites, yet their distribution patterns resemble still those of olivine-clinopyroxene basalts confirming their cogenetic relationship.The suggested crystallization sequence of olivine + clinopyroxene Fe-Ti oxides plagioclase indicates a high-pressure regime (> 5Kbar) in the magma chamber. Corroded and rimmed clinopyroxene-phenocrysts and the comparison of rims with matrix minerals suggest stepwise pressure release due to adiabatic ascent of magma batches and crystallization under varying conditions.The rocks are classified as within-plate alkali basalts and their fractionation products. Magma genesis is suggested to have been triggered by rifting of the passive European continental margin. Consequent compression indicated by uplift and erosion of the surface, however, prohibited the bulk magma from further ascent causing high-pressure fractionation with only small magma batches reaching the surface.

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Mehrphasige Entwicklung der Magmenabfolge im östlichen Mecsek-Gebirge, Süd- Ungarn

Zusammenfassung Anhand von Haupt- und Spurenelementanalysen sowie mineralogischen Untersuchungen wird ein magmagenetisches Modell für die Abfolge der Vulkanite im östlichen Mecsek-Gebirge (Süd-Ungarn) vorgeschlagen.Spurenelementverteilungsmuster dieser Vulkanite weisen auf eine Ausgangsschmelze aus einem wiederangereicherten Mantel hin. Relativ niedrige Cr- und Ni-Gehalte und niedrige Mg#, selbst in den am wenigsten fraktionierten Olivin Clinopyroxen-Basalten, zeigen eine Fraktionierung derOlivin-Klinopyroxen-basaltischen Magmen noch vor deren Aufstieg an, was durch glomerophyrische Klinopyroxene mit Forsterit-reichen Olivinen bestätigt wird. Die folgende Fraktionierung von weiteren 35% des Olivin-Klinopyroxen-basaltischen Magmas führte zuPlagioklas-basaltischen Magmen, die Olivin-frei sind. Statt Olivin wurden Plagioklas und Erzphasen die vorherrschenden kristallisierenden Phasen. Nach etwa 60% Fraktionierung bildeten sich aus der RestschmelzeMugearite. Diese sind an Ni und Cr sowie an Fe, Ti und V verarmt, was auf die zusätzliche Fraktionierung von Fe-Ti Oxiden zurückgeführt wird.Tephriphonolith-Gänge bildeten sich durch weitere Fraktionierung (70–80%), wobei Apatit und Feldspat als fraktionierende Phasen zunehmend wichtiger wurden. DiePhonolithe repräsentieren eine Restschmelze von 15–20% bezogen auf die Olivin-Clinopyroxenbasaltische Schmelze, die den Berechnungen zugrunde liegt. Sie zeichnen sich durch eine starke Verarmung an allen kompatiblen Elementen sowie Ti and V, durch steigende Zr/Hf-Verhältnisse aufgrund von Klinopyroxen- und Fe-Ti-Oxid-Fraktionierung, durch Verarmung an P und mittleren Seltenerdelementen durch Apatit-Fraktionierung und durch eine Abnahme von Sr, Ba und Eu durch Fraktionierung von Feldspäten aus. Inkompatible Spurenelemente wie die Seltenerdelemente, Zr, Hf, Nb, Ta und Rb erreichen in den Phonolithen Höchstwerte. Ihre Verteilungsmuster ähneln jedoch noch immer jenen der Olivin-Klinopyroxen-Basalte, was ihre kogenetische Beziehung bestätigt.Die ermittelte Kristallisationsfolge Olivin + Clinopyroxen Fe - Ti - Oxide Plagioklas spricht für Drucke > 5 Kbar in der Magmenkammer. Korrodierte Clinopyroxen-Phänokristalle mit Anwachssäumen, sowie der Vergleich der Anwachssäume mit Matrixmineralen, sprechen für einen schrittweisen Druckabfall durch adiabatischen Aufstieg einzelner Magmenschübe und Kristallisation unter sich ändernden Bedingungen.Diese Gesteine werden als Intraplatten-Alkalibasalte und deren Fraktionierungsprodukte klassifiziert. Wahrscheinlich wurde die Magmenbildung durch Dehnung im passiven Kontinentalrand Europas ausgelöst. Nachfolgende Kompression, angezeigt durch Hebung und Erosion der Oberfläche, verhinderte jedoch den weiteren Aufstieg der Magmen. Dies bewirkte eine Hochdruck-Fraktionierung, und nur kleine Magmenschübe konnten die Oberfläche erreichen.

     

The status and local stratigraphical context of the Hampen Formation type section (Bathonian,Middle Jurassic)

The type section of the Hampen Formation, as currently defined, is located near Salperton (Gloucestershire); it comprises beds of Middle Jurassic (Bathonian) age. Its validity as a type section is questioned; only the uppermost 2.3 m are herein considered truly to represent the Hampen Formation. The underlying 7.4 m are re-defined as a facies variant of the Througham Formation, for which the name Daglingworth Member is proposed. A review of the local stratigraphical context clarifies the relationship of the Hampen Formation, as newly defined, and of the Daglingworth Member, to contiguous stratigraphical units.     

Geochemistry and petrogenesis of the Early Cretaceous continental rift-type volcanic rocks of the Mecsek Mountains, South Hungary

Early Cretaceous volcanic rocks (basanite to phonolite) from the Mecsek Mountains (South Hungary) represent the products of Late Mesozoic extension-related alkaline magmatism at the southern margin of the European plate. Two mafic groups have been distinguished: ankaramite-alkali basalt and Na-basanite-phonotephrite. Phonolites could have been formed from the Na-basanitic magma by low-pressure fractionation. The major and trace element characteristics of the Mecsek basalts are similar to those of alkaline basalts of other intraplate areas and have a St. Helena-type OIB affinity. The mantle source of the Mecsek volcanics could be similar to that proposed by Wilson and Downes (1991) as one of the mantle endmembers for extension-related Tertiary-Quaternary alkaline basalts in Europe. Geochemical modelling indicates that the primary magmas of the Na-basanite series were formed by about 4% partial melting, whereas ankaramites and alkali basalts originated by about 6% partial melting of a garnet-peridotite source.     

Two new stephanoceratid ammonites from the Aalenian-Lower Bajocian (Middle Jurassic,Dorset, UK) and their phylogenetic significance

Two new species of stephanoceratid ammonites are erected: Stephanoceras (Riccardiceras) eoeteosum sp. nov. and Stephanoceras (Skirroceras) englandi sp. nov. from the Inferior Oolite Formation of Dorset, UK. They represent the first and last members of a chronocline of serpenticonic morphospecies. The stratigraphical position of Rhytostephanus rhytus Buckman is reviewed, necessitating a change in the faunal horizon scheme. The term mesoconch is proposed for use in describing microsomic macroconchs, the function of which is considered. Names applied to morphospecies and their uses are reviewed. The role of conservation is discussed in respect of preserving Dorset Inferior Oolite exposures.     

柴西阿尔金山前下中侏罗统沉积地球化学特征及意义

依据柴达木盆地西部阿尔金山前红沟子北部地区黑石山地质调查,结合样品的地球化学分析资料,对该区下中侏罗统的沉积特征和沉积环境进行了详细研究。其结果表明柴西阿尔金山前黑石山山顶下中侏罗统层位在横向上不见其相同层位,且岩性特征与山底区别较大,判断山顶上的下中侏罗统可能为“飞来峰”;柴西阿尔金山前下中侏罗统的沉积环境为还原环境,有利于有机质的保存和烃源岩的生成,具有一定的油气勘探前景。     

赣南中侏罗世正长岩-辉长岩的起源及其地质意义

正长岩-辉长岩组合的形成通常与板内伸展构造有关,它们可由同源岩浆演化形成,也可以由两种独立起源的岩浆结晶形成.本文选择赣南晚中生代早期黄埠正长岩和车步辉长岩进行了详细的年代学和岩石地球化学研究,旨在探讨它们的起源及其与岩石圈地幔演化的关系.LA-ICP-MS锆石U-Pb定年结果表明：黄埠正长岩和车步辉长岩形成于≈178Ma,为同时期岩浆作用的产物.主量元素、微量元素和Nd同位素地球化学特征表明它们并非由同源岩浆演化形成.初步研究表明,黄埠正长岩和车步辉长岩可能都起源于受软流圈来源熔体交代富集的岩石圈地幔,熔融发生在上地幔尖晶石-石榴石相转换带深度,且岩浆在结晶演化过程中发生了较低程度的地壳混染作用.与车步辉长岩相比,黄埠正长岩有高的不相容元素含量、Ce/Yb、La/Yb、Sm/Yb比值和高的εNd（t）值,表明黄埠正长岩的岩浆起源相对更深,且其岩石圈地幔源区经历了更高程度的交代作用.因此,赣南正长岩-辉长岩是板内伸展构造背景下,不同程度软流圈-岩石圈相互作用的反映.     

A revision of the Jurassic (Bathonian to Oxfordian) lithostratigraphy of the onshore Moray Firth Basin,north-east Scotland

Bathonian to Oxfordian strata occur onshore in two principal locations over 30 km apart on the coast of the Moray Firth, at Brora and Balintore. The existing lithostratigraphy has the same formation names applied to both successions despite profound differences, exemplified in their schemes of local members. Furthermore, three of the formation names include the same place name, and use obsolete lithological terms.     

藏北聂荣县查吾拉区中侏罗统巴通阶与基底岩系角度不整合的发现及其地质意义

在聂荣县查吾拉区一带首次发现中侏罗统巴通阶与下伏前奥陶系基底变质岩系之间呈角度不整合接触在包括查吾拉区在内的索县——左贡地层分区中．中侏罗统仅有巴通阶超覆不整合于“浅基底”变质岩系之上。反映了南、北羌塘盆地之间的中央隆起带不仅在双湖一带发育,而且在查吾拉区以东地区同样也发育。这一发现对该地层分区构造古地理的研究具有重要意义。     

Palaeobiogeographic implications of Late Bajocian-Late Callovian (Middle Jurassic) dinoflagellate cysts from the Central Alborz Mountains, northern Iran

The Dalichai Formation with an age of Late Bajocian-Late Callovian was sampled in Central Alborz Mountains of northern Iran and studied for palynological, palaeobiogeographical and palynocorrelation purposes. Palynological studies revealed diverse and well-preserved dinoflagellate cyst assemblages and lead to identification of three zones i.e., Cribroperidiniumcrispum (Late Bajocian), Dichadogonyaulaxsellwoodii (Bathonian to Early Callovian) and Ctenidodiniumcontinuum (Early to Middle Callovian) Zones. Subzone a of the D. sellwoodii Zone (Early to Middle Bathonian) was also differentiated. This biozonation corresponds to those recognised in Northwest Europe. Furthermore, the ammonoid families recorded including Phylloceratidae, Oppeliidae, Reineckeiidae, Perisphinctidae, Haploceratidae, Parkinsoniidae and Sphaeroceratidae, which confirm the Late Bajocian to Late Callovian age, are quite similar to those of Northwest Europe and the northwestern Tethys. The close similarities of the dinoflagellate cyst assemblages and ammonite fauna of northern Iran with those of Northwest Europe and the northwestern Tethys during the Middle Jurassic indicate direct but episodic marine connection and faunal exchange between the two areas.     

Palaeontology,stratigraphy and sedimentology of Woodeaton Quarry (Oxfordshire) and a new microvertebrate site from the White Limestone Formation (Bathonian,Jurassic)

Woodeaton Quarry in Oxfordshire has previously yielded a number of large sauropod vertebrae and other (unpublished) dinosaur remains from a horizon in the Rutland Formation. No review of the wider terrestrial fauna from Woodeaton has been published to date. Here we present an overview of new material recovered from a microvertebrate site at the top of the White Limestone Formation (Middle Jurassic, Bathonian, Great Oolite Group, Retrocostatum Zone) and review the stratigraphy to provide a comprehensive local stratigraphic framework and place the quarry in the correct regional context. The terrestrial fauna is similar to that found from other UK Bathonian microvertebrate sites and includes probable dromaeosaurid theropods, ornithischians, tritylodontids and mammaliaforms such as amphitheriids, docodonts, ‘eutriconodonts’, ‘haramyids’ and multituberculates. Placement of the White Limestone Formation boundaries are clarified with respect to the Rutland and Forest Marble Formations. This indicates that the microvertebrate bed from Woodeaton is slightly older than that of the well-known mammal bed from nearby Kirtlington Quarry.     

Skeletal halites from the Jurassic of Massachusetts, and their significance

Pseudomorphs after skeletal halite occur in a bed of Lower Jurassic lacustrine shale at Holyoke, Massachusetts. The pseudomorphs include pagoda types similar to those described by Southgate and show dissolution furrows. However the shales were deposited in a permanently subaqueous rather than an emergent environment, and the pseudomorphs accordingly grew in brine-saturated sediment. Evaporation to dryness is not therefore essential to the genesis of skeletal halite.     

Late Middle Jurassic (Late Bathonian-early Callovian) radiolarian cherts from the Neotethyan Bornova flysch zone, Spil Mountains, Western Turkey

Alternating radiolarian cherts and mudstones associated with basaltic lavas occur in a olistolith within the Late Cretaceous Bornova Flysch in W Anatolia. Cherts yielded diverse and moderately preserved, Nassellaria-dominated radiolarian faunas of late Bathonian-early Callovian age. Associated volcanic rocks are geochemically classified as remnants of oceanic seamounts. This is so far the first late Middle Jurassic age from the crust of the Neotethyan Izmir-Ankara Ocean in W Anatolia, and suggests that its spreading started earlier. Similar ages were reported from the Vardar and Meliata-Hallstadt Tethyan oceanic branches in Greece and Serbia, which also opened in Late Triassic but closed earlier. Published in Russian in Stratigrafiya. Geologicheskaya Korrelyatsiya, 2009, Vol. 17, No. 3, pp. 70–80. The article is published in the original.     

大兴安岭火山岩带中北部中侏罗世中酸性火山岩的厘定及其地质意义

通过对大兴安岭火山岩带中北部地区北岸林场一带中酸性火山岩进行地球化学、锆石U-Pb年代学特征研究,探讨其形成的年代及构造背景。LA-ICP-MS锆石U-Pb同位素测年表明,中酸性火山岩形成时代为(166±1) Ma,属于中侏罗世,岩性为粗面英安岩和粗安岩。在主量元素组成上,SiO_2含量为59.58%～68.34%,(Na_2O+K_2O)为7.78%～8.84%,K_2O/Na_2O值为0.73～0.82,MgO含量为0.75%～2.67%,Mg~#值为25.5～44.4,显示岩石相对富硅、富钠、低钾、碱含量偏高、镁含量偏低的特征。TAS分类图及铝饱和指数A/CNK(0.91～0.97)显示岩石具有准铝质偏碱性的特征。稀土元素总量中等,轻、重稀土分馏明显(La/Yb)_N=6.56～11.79,具有弱的Eu负异常(δEu=0.60～0.81);微量元素相对富集大离子亲石元素Rb、Th、U,贫高场强元素Nb、Ta、Hf、Ti。地质、地球化学分析表明中酸性火山岩为地壳物质部分熔融的产物。岩浆活动可能起源于早侏罗世蒙古—鄂霍茨克洋闭合过程中造山晚期构造环境,但在中侏罗世张性构造环境喷发成岩,提供了俯冲造山环境形成的岩浆在地壳中可能跨时、跨构造环境活动的范例。     

贵州安龙坡脚剖面中三叠世安尼期牙形石的发现及其意义

贵州安龙坡脚剖面新苑组位于扬子地台和右江盆地交汇处,为中三叠世台缘斜坡相沉积,在该组中上部发现了牙形石动物群,除少量分枝分子外,都归属于Neogondolella属,建立了4个牙形石带,自下而上分别为:Neogondolella bulgarica、Neogondolella bifurcata、Negondolella constricta、Neogondolella constricta cornuta(未见顶界)带。时代为中三叠世安尼中晚期,其特殊的古地理位置,对系统研究与对比罗平生物群、盘县动物群的古生态环境,以及区域地层对比、地层格架建立,探讨该时期盆地演化提供了基础资料。     

Origin and geodynamic significance of Upper Cretaceous lamprophyres from the Villány Mts (S Hungary)

Summary In the Villány Mts of southern Hungary, ocelli-bearing porphyritic lamprophyre dykes and sills of Upper Cretaceous age occur sporadically, intruding Mesozoic carbonate rocks. They at places contain metasomatised mantle xenoliths and quartz xenocrysts of crustal origin. They are moderately fractionated with significant LILE and LREE enrichments and a notable Nb–Ta negative anomaly. Trace elements indicate that they formed in an intraplate environment by very low degree partial melting of a metasomatised garnet lherzolite mantle source that was enriched by earlier subduction. Based on petrography, geochemistry and age constraints, they differ from other Mesozoic basic rocks of the Tisza block (Mecsek Mts and Slavonian basalts); however, they show a significant geochemical similarity to the Upper Cretaceous lamprophyre dyke swarm from NE Transdanubia (northwestern Hungary) situated on the Alcapa microplate. Thus we suggest that lamprophyres from the Villány Mts and NE Transdanubia could have originated from the same or similar enriched asthenospheric mantle sources.