2006年秋季长江口及其邻近水域浮游植物群集

根据2006年11月在长江口及其邻近水域(30°30′N～32°30′N,121°E～123°30′E)39个测站采集的浮游植物水样研究了该水域浮游植物群集特征。调查区浮游植物以硅藻和甲藻为主,此外还有少量的金藻、蓝藻和绿藻。浮游植物细胞丰度介于0.13～59.69个/mL之间,平均为4.39个/mL,主要优势物种为圆海链藻Thalassiosira rotula和骨条藻Skeletonema spp.,调查区两个细胞丰度密集区分别出现在靠近口门以及外海水域。浮游植物细胞在20m层出现最大值。调查区两个典型断面的浮游植物分布特征分别由骨条藻和圆海链藻所刻画。固氮蓝藻铁氏束毛藻Trichodesmium thiebautii主要出现在调查区东部水域表层。根据浮游植物物种和细胞丰度进行聚类分析后,发现存在调查区东部与近岸2个浮游植物分区。     

Early deformation fabrics of melange in the Mesozoic Waipapa Terrane, North Island, New Zealand

Abstract The Waipapa Terrane in northern North Island, New Zealand, is a Mesozoic accretion-ary complex formed along the Gondwana margin. It contains abundant melange rocks with distinctive characteristics. Precise analyses of their mesoscopic fabrics in Waiheke Island near Auckland have revealed the following sequence of deformation. The earliest phase of deformation of the sandstone/mudstone association, which is the main constituent of this terrane, originated by chaotic mixing of sand and mud due to liquidization of water-saturated, poorly consolidated sediments. The second phase was characterized by hydrofracturing and subsequent forceful injection of ductile mud into rather brittle sand. Local intrusions of sand forming dykes and sills followed these events, as well as intrusions of pelagic/hemipelagic green argillite originally underlying the sandstone/mudstone association. An abundant occurrence of these mixing and multi-stage injection/intrusion fabrics strongly suggest that the Waipapa Terrane around the study area was a site of high pore-fluid pressure. Scaly-foliated melange fabrics with monoclinic symmetry, originating from layer-parallel shearing, were then locally superimposed on the pre-existing melange fabrics. Similar scaly-foliated fabrics also developed in the chert beds originally intercalated between the green argillite and the uppermost part of the oceanic crust. These scaly fabrics might have been related to the regional stacking and juxtaposition of the accreted sediments. The sequence and variation in style of deformation forming the melange fabrics presumably reflected changes in porosity and state of compaction of accreted sediments in a shallow tectonic level.     

Deep reflection seismic imaging of the internal zone of the South Armorican Hercynian belt (western France) (ARMOR 2/Géofrance 3D Program)

We present results and interpretation of a 72 km long deep seismic reflection profile acquired across the internal zone of the Hercynian belt of South Brittany. The profile is of excellent quality, most of the crust being highly reflective. The “ARMOR 2 South” profile, is correlated with the “ARMOR 2 North” profile that was published in 2003. Correlation of the main subsurface reflections with surface geological and structural data provides important information about the crustal structure that resulted from thickening during Late Devonian and regional-scale extension during Late Carboniferous. In particular, seismics image shows a very high reflectivity zone, lying flat over more than 40 km at about 10–12 km depth. This zone is interpreted as a major zone of ductile crustal thinning.     

Paleomagnetic and 40Ar/39Ar geochronological results from the Linzizong Group,Linzhou Basin,Lhasa Terrane,Tibet: Implications to Paleogene paleolatitude and onset of the India–Asia collision

The Linzizong Group (64–44 Ma) of the Lhasa Terrane in Tibet is critically positioned for establishing the paleoposition of the southern leading edge of the Asian continent during Paleogene times and constraining onset of the India–Asia collision. Here we report paleomagnetic results from a collection comprising 384 drill-core samples from 34 sites embracing all three formations of this group. Comprehensive demagnetization and field tests isolate characteristic remanent magnetizations (ChRM) summarized by overall tilt-corrected formation-mean directions of D = 183.6°, I = −12.4° (α₉₅ = 8.1°) for the Dianzhong (64–60 Ma), D = 1.0°, I = 18.1° (α₉₅ = 8.1°) for the Nianbo (60–50 Ma), and D = 12.4°, I = 23.2° (α₉₅ = 7.3°) for the Pana (50–44 Ma). Fold tests are positive in each formation suggesting a pre-folding origin and we interpret the magnetizations as quasi-primary and acquired at, or slightly later than, formation of the Linzizong Group. Revised Paleogene paleopoles with Ar–Ar age constraints for the Lhasa Terrane indicate that onset of the India–Asia collision occurred no later than ∼60.5 ± 1.5 Ma at a low paleolatitude of ∼10°N. Analysis of 60 site-mean observations from a range of studies of the Pana Formation in the higher part of the succession highlight a large dispersion of ChRM directions; a number of possible causes are suggested but further study of this formation over a wider area is required to resolve this issue.     

Ostracoda (Arthropoda,Crustacea) in a Miocene oxygen minimum zone,Trinidad, West Indies: A test of the Platycopid Signal Hypothesis

Studies of Recent ostracodes around the area of South America shed little light on the paleoenvironmental interpretation of Miocene assemblages. Consequently, interpretations of the Miocene ostracode assemblages must be supplemented using evidence from better documented taxa. Benthic foraminifera in samples from the Lower to Middle Miocene Brasso Formation at Brasso Village, Trinidad, have previously been used to distinguish three sample groupings (Beneath, Within and Above) around an oxygen minimum zone (OMZ), this being a layer of water within which dissolved oxygen concentrations can be as low as 0.1–1.0 mL/L. Using these same samples and the foraminiferal assemblage demarcations relative to the OMZ, this paper examines the associated and rich ostracode fauna of the Brasso Formation.The mean recovery of ostracode valves per sample was approximately three times greater in the Within OMZ sample group than in either of the Beneath OMZ or Above OMZ groups, perhaps reflecting the exclusion of macro-predators from within the OMZ. Individual rarefaction of species richness S to N = 300 valves was conducted for each sample group. This showed that S did not differ between the sample groups, ranging from 22.4 to 24.8. We used all ostracode species to model group separation. Based upon the Mahalanobis’ criterion, we obtained significant group separation using a model with four taxa: Munseyella ex gr. minuta, Argilloecia posterotruncata, Munseyella sp. and Xestoleberis sp., while a fifth, Argilloecia spp., provided a significant but minor increase in separation probabilities over all groups. The two most abundant species (Bradleya sp., Gangamocytheridea reticulata) were thus not the best species for detecting the OMZ. Platycopid ostracodes of the genus Cytherella were found throughout the section, rather than concentrated within the OMZ, which contradicts the Platycopid Signal Hypothesis that OMZs are characterized by platycopid dominance. The total distribution and turnover of both ostracodal and foraminiferal assemblages were compared and contrasted quantitatively using a total assemblage turnover index (ATI) and the paleoenvironmental importance evaluated. The correlated between-sample ATI is for both groups lowest within the OMZ.     

Early Cambrian Ichnofossils from the Mussoorie Syncline and revision of Trace Fossil Biozonation of the Lesser Himalaya,India

A new locality bearing ichnofossils of the Cruziana Assemblage Zone-Ⅲ from the Mussoorie syncline,Lesser Himalaya,is located in rocks of Member-B of the Dhaulagiri Formation,Tal Group,exposed along the Maldewta-Chhimoli fresh road cut section.The site yielded ichnofossils Bergaueria perata,Cochlichnus anguineus,？Diplocraterion isp.,Dimorphichnus obliquus,diplichnitiform Cruziana bonariensis,Diplichnites gouldi,Glockeria isp.,Helminthopsis isp.,Monomorphichnus lineatus,Phycodes palmatum,Palaeophycus striatus,Planolites beverleyensis,Planolites montanus,Treptichnus cf.T.pedum,scratch marks and an undetermined worm impression.An Early Cambrian age （Cambrian Series 2） is assigned to the ichnofossil-bearing strata based on the stratigraphic position between the Drepanuroides and Palaeoolenus trilobite zones.A revised Cambrian ichnofossil zonation is presented for the Tal Group of the Mussoorie syncline.Together with their occurrence on rippled surfaces,and the lateral displacement of some trackways （due to current action）,a sub-aqueous shallow-marine depositional setting is proposed for the rocks of Member-B.     

Cleantech clusters: Transformational assemblages for a just,green economy or just business as usual?

The rhetorical zeal for green enterprise as a global fix for the tripartite challenges of economic recession, environmental degradation and social inequality is increasingly visible in state and non-state pronouncements around the globe under the banner of ‘The Green Economy’. In particular, many policy-facing statements call for transitions leading to a transformation in development practices. Yet there is little detail either in policy or research regarding the types of transitions needed and how they are to be initiated, nor agreement about what a transformed economy might look like. Despite this, there are emergent activities within the cleantech arena which are being heralded as actually existing examples of green economy activities. One means through which these activities are seeking to exert influence over development trajectories is by clustering both at the subnational and transnational level. While diverse in formation, many of these clusters are hybridised, involving actors from public, private and civil society sectors. Critiquing the efficacy of mainstream industrial cluster theory to analyse hybridised cleantech clustering, this paper presents a unique synthesis of current thought on multiscalar environmental governance and socio-spatial formations to explore the practices and potentialities of these hybridised cleantech clusters. Surveying the landscape of cleantech clustering and meta-clustering, before focusing in depth on one case study, the contribution of clustering to transitioning towards a transformed green economy is considered. Despite strong forces, both within and beyond cleantech clusters, for maintaining neoliberalised approaches to cleantech activity, it is concluded that for as long as cleantech clusters remain open and inclusive of actors proposing alternative pathways they do represent potential, albeit provisional, assemblages for transformation.     

Narooma Terrane: Implications for the construction of the outboard part of the Lachlan Orogen

In its type area around Narooma, the Narooma Terrane in the Lachlan Orogen comprises the Wagonga Group, which consists of the Narooma Chert overlain by the argillaceous Bogolo Formation. Conodonts indicate that the lower, largely massive (ribbon chert) part of the Narooma Chert ranges in age from mid-Late Cambrian to Darriwilian-Gisbornian (late Middle to early Late Ordovician). The upper Narooma Chert consists of shale, containing Eastonian (Late Ordovician) graptolites, interbedded with chert. Where not deformed by later faulting, the boundary between the Narooma Chert and Bogolo Formation is gradational. At map scale, the Narooma Terrane consists of a stack of imbricate thrust slices caught between two thrust faults that juxtaposed the terrane against the coeval Adaminaby Superterrane in Early Silurian time. These slices are best defined where Narooma Chert is thrust over Bogolo Formation. The soles of such slices contain multiply foliated chert. Late extensional shear bands indicate a strike-slip component to the faulting. The Narooma Terrane, with chert overlain by muddy ooze, is interpreted to be an oceanic terrane that accumulated remote from land for ～50 million years. The upward increase in the terrigenous component at the top of the Wagonga Group (shale, argillite, siltstone and sandstone of the upper Narooma Chert and Bogolo Formation) records approach of the terrane to the Australian sector of the Gondwana margin. Blocks of chert, argillite and sandstone reflect extensional/strike-slip disruption of the terrane as it approached the transform trench along the Gondwana-proto-Pacific plate boundary. Blocks of basalt and basalt breccia represent detritus from a seamount that was also entering the trench. There is no evidence that the Narooma Terrane or the adjacent Adaminaby Group formed in an accretionary prism/ subduction complex.     

胶北地体早前寒武纪重大岩浆事件、陆壳增生及演化

早前寒武纪重大岩浆事件是早期陆壳增生及演化的主要地质作用。本文通过系统总结最近几年胶北地体早前寒武纪重大岩浆事件代表性岩石的岩相学、锆石U-Pb年代学、岩石地球化学及锆石Hf同位素研究的最新成果,厘定出太古宙~2.9Ga、2.7Ga及2.5Ga三期以TTGs岩浆事件为代表的陆壳增生事件。这些TTGs具有典型太古宙高铝TTGs的地球化学特征及正的εHf(t)值,锆石Hf模式年龄主要集中在ca.3.2~2.7Ga。两种不同的构造模式被用来理解胶北太古宙TTGs(陆壳)的成因:(1)加厚基性下地壳的部分熔融;(2)俯冲洋壳的部分熔融。根据胶北TTGs在时间上呈事件性侵位,空间上呈面状分布,以及相对较低的Mg#、Cr及Ni含量,前者可能更适合胶北TTGs的成因。确定了胶北古元古代2.2~2.0Ga黑云母/角闪石二长花岗片麻岩及~1.8Ga以二长(正长)花岗岩为代表的多期陆壳重熔事件。综合这些研究结果,初步总结出胶北早前寒武纪陆壳形成及演化历史:1)2.9Ga,主要为基性地壳(洋壳)的增生,并可能存在规模有限的、被剥蚀殆尽的太古宙早期陆壳;2)在~2.9Ga、~2.7Ga及~2.5Ga,由于地幔(热)柱上涌,ca.3.3~2.7Ga新生的加厚基性玄武质下地壳发生事件性部分熔融,并伴随有早期陆壳的重熔,形成主要由TTGs及少量陆壳重熔型(高钾)花岗岩组成的太古宙陆壳;3)ca.2.2~2.0Ga,可能由于地幔物质上涌,陆壳伸展,形成裂谷,陆壳物质重熔,形成ca.2.2~2.0Ga花岗质岩石;4)ca.1.95~1.85Ga,发生强烈的挤压碰撞构造作用,裂谷闭合,卷入挤压作用的物质发生高角闪岩相到高压麻粒岩相变质;5)~1.8Ga,地幔物质上涌,陆壳伸展减薄,陆壳物质重熔,形成~1.8Ga花岗岩。     

The Saint-Georges-sur-Loire olistostrome,a key zone to understand the Gondwana-Armorica boundary in the Variscan belt (Southern Brittany,France)

In the southern part of the French Armorican massif, the Ligerian domain is located along the boundary between Gondwana and Armorica. Lithological, geochemical and structural data on the Saint-Georges-sur-Loire Unit, which is the northern part of the Ligerian domain, allow us to distinguish two sub-units. A southern sub-unit, formed by various blocks (chert, limestone, sandstone, rhyolite, mafic rocks) of Silurian to Middle Devonian age included as olistoliths in a Middle-Late Devonian terrigeneous matrix, overthrusts a sandstone-pelite northern sub-unit. Both units experienced two deformation events. The first one is a top-to-the-NW thrusting and the second one is a left-lateral wrenching. The Saint-Georges-sur-Loire Unit is an accretionary prism formed during the Late Devonian closure of the Layon rift, coeval with the main phase of the Variscan orogeny. The Layon rift, which according to the mafic olistoliths was partly floored by oceanic crust, appears as a buffer structural zone that accounts for the lack in Central Brittany of any tectonic or sedimentary echo of the closure of the Medio-European Ocean. The tectonic evolution of the Saint-Georges-sur-Loire Unit supports a polyorogenic model for this part of the Variscan Belt.