Interplay of orbital forcing and tectonic pulses in the Cambrian Iberian platform, NE Spain     

J. J. Álvaro  E. Vennin  A. Muñoz  B. Sánchez-Valverde  J. L. Ojeda 《International Journal of Earth Sciences》2000,89(2):366-376

The stratigraphy of carbonate/shale couplets, cycles and cycle-stacking patterns in a Cambrian shallow water platform (Iberian Chains, NE Spain) are related to sea-level changes driven by orbital forcing and by tectonic pulses. The interplay of both effects can be discriminated in the Iberian fault-controlled platform, in which the tectonic activity can be analysed by accurate and detailed biostratigraphic correlations based on trilobite zonation. The stratigraphic hierarchy of rhythmically interbedded limestones and shales, in two coeval but structurally separated geodynamic settings, yields cycle ratios of 1.44 :1. This ratio is supported by time thickness and spectral analysis, which is based on a graphic method of analysis: the Map of Grey Lines. The cycle ratio seems to be evidence for orbital forcing by obliquity and precession cycles predicted for early Paleozoic time. Carbonate/shale couplets, the smallest rhythmic units recognisable in the field, represent short-term, periodic fluctuations in supply of terrigenous sediments and carbonate productivity of uncertain origin, which could be associated with one of several harmonics of the former orbital cycles. The pulsating tectonic activity was approximated by using a quantitative analysis of tectonically induced subsidence (Shaw method). Recurrence frequencies of tectonic pulses were estimated and dated by biostratigraphy. As a result, tectonic disturbances in the Cambrian Iberian platform show an episodic periodicity comparable to that of orbital eccentricity cycles, which could mask their recognition. Received: 15 November 1999 / Accepted: 9 February 2000  相似文献   

Assessing biomarker syngeneity using branched alkanes with quaternary carbon (BAQCs) and other plastic contaminants     

Jochen J. Brocks  Emmanuelle Grosjean 《Geochimica et cosmochimica acta》2008,72(3):871-888

Biomarker molecules are valuable for the elucidation of ancient microbial ecosystems and the characterization of petroleum source rocks. For such studies, acquisition of reliable hydrocarbon data and proof of their syngeneity are essential. However, contamination of geological samples with anthropogenic petroleum products during drilling, storage and sampling can be particularly problematic because these hydrocarbons may over-print an original indigenous biomarker profile. To evaluate the extent of contamination of drill core and outcrop material, we studied the distribution of hydrocarbons in 26 rocks from different locations in the world. All rocks had petroleum products on their exterior surfaces. Twenty-two samples also contained surficial hydrocarbons derived from polyethylene plastic, including branched alkanes with quaternary carbon centers (BAQCs) and alkylcyclopentanes with pronounced even-over-odd carbon number preference. Using three examples from the Paleoproterozoic Tawallah and McArthur Groups in northern Australia, we show how indigenous biomarkers can be recognized by comparing hydrocarbon distributions between exterior rock surfaces and the rock interior, and how infiltration of allochthonous hydrocarbons can be assessed through the spatial distribution of characteristic polyethylene derived hydrocarbons in the rock. The methods outlined in this paper give confidence in the interpretation of biomarkers in particularly sensitive applications such as the first occurrences of certain organisms in the geological record and the provenance of organic matter in meteorites.  相似文献   

Upper cretaceous and paleogene sediments from the Northern Kerguelen Plateau     

François Fröhlich  Emmanuelle Wicquart 《Geo-Marine Letters》1989,9(3):127-133

Upper Cretaceous and Paleogene pelagic sediments sampled from the Northern Kerguelen Plateau during cruise MD35 of theMarion Dufresne are described and correlated with the Late Paleogene sequence drilled at site ODP 737 (Leg 119). Taking into account geophysical data obtained by the cruise MD26, a Lower Cretaceous age is computed for the unsampled acoustic basement. A major tectonic/volcanic event in the Late Paleogene, related to rifting, gave rise to a marked unconformity and hiatus termed the “Acoustic Discordance.” Tertiary sediment facies changes were strongly influenced by the evolution of the Antarctic environment.  相似文献   

Geomorphology of a modern carbonate slope system and associated sedimentary processes: Example of the giant Great Abaco Canyon,Bahamas     

Audrey Recouvreur  Natacha Fabregas  Thierry Mulder  Vincent Hanquiez  Kelly Fauquembergue  Elsa Tournadour  Herv Gillet  Jean Borgomano  Emmanuelle Poli  Jean‐Baptiste Kucharski  Stanislas Wilk 《Sedimentology》2021,68(1):266-293

The large acoustic data set acquired during the Carambar cruises is composed of high resolution bathymetry, backscatter data and very‐high resolution seismic lines which allow for an overview of the morphology and sediment transfer processes from the shallow upper slope to the abyssal plain of a modern carbonate system: the north‐eastern slope of the Little Bahama Bank. Surficial distribution of the acoustic facies and echofacies reflects a wide variety of sedimentary processes along and across the slope. The western sector of the Little Bahama Bank is dominated by depositional processes whereas its eastern sector, which is incised in the lower slope by giant canyons, is affected by erosion and bypass processes. Datasets suggest that currents play an important role both in along‐slope sedimentary processes and in the abyssal plain. The Antilles Current appears to affect a large part of the middle and lower slopes. The absence of sizeable present‐day channel/levée complexes or lobes at the mouth of the canyon – revealed by the bathymetric map – indicates that the southward flowing Deep Western Boundary Current influences modern abyssal sediment deposition. Based on depositional processes and indicators of canyon maturity observed in facies distribution, the current study proposes that differential subsidence affects the eastern versus western part of the bank. The morphology of the Great Abaco Canyon and Little Abaco Canyon, which extend parallel to the platform, and the Little Bahama Bank slope appears to be related to the Great Abaco Fracture Zone.  相似文献   

Use of comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry for the characterization of biodegradation and unresolved complex mixtures in petroleum     

Tin C. Tran  Emmanuelle Grosjean  Philip J. Marriott 《Geochimica et cosmochimica acta》2010,74(22):6468-6484

A comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC/TOFMS) method has been developed for separation of a series of petroleum samples using a polar/non-polar column set configuration. Groups of oils were selected to provide samples from the same oil family to assist in comparison of compositional changes during biodegradation. The groups also represented different sources and ages to allow an assessment of the application of GC × GC for the differentiation of oil source, as well as fluid history. The increased resolution and separation afforded by the GC × GC technique provides more complete compositional information on complex biodegraded oil samples than one-dimensional GC, and improves the ability to study biodegradation trends. Among the components identified, it is proposed that alkyl-decahydronaphthalenes constitute a significant contribution to the UCM.  相似文献   

Glacial influence on Neoproterozoic sedimentation: the Smalfjord Formation, northern Norway – reply     

Emmanuelle Arnaud  Carolyn H. Eyles† 《Sedimentology》2004,51(6):1423-1430

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Glacial influence on Neoproterozoic sedimentation: the Smalfjord Formation, northern Norway   总被引：1，自引：0，他引：1  

Emmanuelle Arnaud  Carolyn H. Eyles† 《Sedimentology》2002,49(4):765-788

ABSTRACT There is much debate regarding the intensity and geographic extent of glaciation during the Neoproterozoic, particularly in response to recent geochemical work suggesting that the Neoproterozoic earth was at times ice covered from equator to poles (the ‘Snowball Earth’ hypothesis). A detailed sedimentological analysis of the Neoproterozoic Smalfjord Formation of northern Norway was conducted in order to determine the extent and intensity of glacial influence on sedimentation. In the Tarmfjorden area, the Smalfjord Formation consists of a stacked succession of diamictites interbedded with fine‐grained laminated mudstones containing rare outsized clasts. Diamictites and interbedded mudstones are interpreted as the product of subaqueous mass flows generated along the basin margin. In the Varangerfjorden area, chaotically interbedded diamictites, conglomerates and sandstones are overlain by a thick succession of stacked sandstone beds; onediamictite unit at Bigganjargga overlies a striated pavement. The Varangerfjorden outcrops appear to record deposition on a subaqueous debris apron. Although diamictites contain rare striated and faceted clasts, suggesting a glacial sediment source, their origin as subaqueous mass flows prevents the interpretation of ice mass form or distribution. Rare lonestones may be associated with floating ice in the basin, which may be of glacial or seasonal origin. Glacial ice may have contributed poorly sorted glacial debris to the basin margin, either directly or through fluvioglacial systems, but there is no evidence of direct deposition by ice at Varangerfjorden or Tarmfjorden. The overall fining‐upward trend identified in the Smalfjord Formation and overlying Nyborg Formation is consistent with depositional models of rift basin settings. This fining‐upward trend, the predominance of mass flow facies including breccias associated with scarps and the evidence for extensional tectonic activity in the region suggest that tectonic activity may have played an important role in the development of this Neoproterozoic succession. The Smalfjord Formation at Tarmfjorden and Varangerfjorden does not exhibit sedimentological characteristics consistent with severe glacial conditions suggested by the snowball Earth hypothesis.  相似文献   

Bruns' Theorem: The Proof and Some Generalizations     

Emmanuelle Julliard-Tosel 《Celestial Mechanics and Dynamical Astronomy》2000,76(4):241-281

We give here a proof of Bruns’ Theorem which is both complete and as general as possible: Generalized Bruns’ Theorem.In the Newtonian (n+1)-body problem in ℝ ^p with n≥2 and 1≤p≤n+1, every first integral which is algebraic with respect to positions, linear momenta and time, is an algebraic function of the classical first integrals: the energy, the p(p−1)/2 components of angular momentum and the 2p integrals that come from the uniform linear motion of the center of mass. Bruns’ Theorem only dealt with the Newtonian three-body problem in ℝ³; we have generalized the proof to n+1 bodies in ℝ^p with p≤n+1. The whole proof is much more rigorous than the previous versions (Bruns, Painlevé, Forsyth, Whittaker and Hagiara). Poincaré had picked out a mistake in the proof; we have understood and developed Poincaré’s instructions in order to correct this point (see Subsection 3.1). We have added a new paragraph on time dependence which fills in an up to now unnoticed mistake (see Section 6). We also wrote a complete proof of a relation which was wrongly considered as obvious (see Section 3.3). Lastly, the generalization, obvious in some parts, sometimes needed significant modifications, especially for the case p=1 (see Section 4). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The offshore east African rift system: new insights from the Sakalaves seamounts (Davie Ridge,SW Indian Ocean)          下载免费PDF全文

Simon Courgeon  Patrick Bachèlery  Gwénael Jouet  Stephan J. Jorry  Esther Bou  Marcelle K. BouDagher‐Fadel  Sidonie Révillon  Gilbert Camoin  Emmanuelle Poli 《地学学报》2018,30(5):380-388

The offshore branch of the East African Rift System (EARS) has developed during Late Cenozoic time along the eastern Africa continental margin. While Neogene–Pleistocene extensional tectonic deformation has been evidenced along the northern segment of the Davie Ridge, the spatial extent of deformation further south remains poorly documented. Based on recent and various oceanographic datasets (bathymetric surveys, dredge samples and seismic profiles), our study highlights active normal faulting, modern east–west extensional tectonic deformation and Late Cenozoic alkaline volcanism at the Sakalaves Seamounts (18°S, Davie Ridge) that seem tightly linked to the offshore EARS development. In parallel, rift‐related tectonic subsidence appears responsible for the drowning of the Sakalaves Miocene shallow‐water carbonate platform. Our findings bring new insights regarding the development of the EARS offshore branch and support recent kinematic models proposing the existence of a plate boundary across the Mozambique Channel.  相似文献   

Linear Gaussian state-space model with irregular sampling: application to sea surface temperature   总被引：1，自引：1，他引：0  

Pierre Tandeo  Pierre Ailliot  Emmanuelle Autret 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(6):793-804

Satellites provide important information on many meteorological and oceanographic variables. State-space models are commonly used to analyse such data sets with measurement errors. In this work, we propose to extend the usual linear and Gaussian state-space to analyse time series with irregular time sampling, such as the one obtained when keeping all the satellite observations available at some specific location. We discuss the parameter estimation using a method of moment and the method of maximum likelihood. Simulation results indicate that the method of moment leads to a computationally efficient and numerically robust estimation procedure suitable for initializing the Expectation–Maximisation algorithm, which is combined with a standard numerical optimization procedure to maximize the likelihood function. The model is validated on sea surface temperature (SST) data from a particular satellite. The results indicate that the proposed methodology can be used to reconstruct realistic SST time series at a specific location and also give useful information on the quality of satellite measurement and the dynamics of the SST.  相似文献