Mesozoic and Cenozoic vertical movements in the Atlas system (Algeria, Morocco, Tunisia): An overview   总被引：5，自引：0，他引：5  

Dominique Frizon de Lamotte  Pascale Leturmy  Sami Khomsi  Omar Saddiqi  André Michard 《Tectonophysics》2009,475(1):9-28

The E-W trending Atlas System of Maghreb consists of weakly shortened, intra-continental fold belts associated with plateau areas (“Mesetas”), extending between the south-westernmost branch of the Mediterranean Alpine Belt (Rif-Tell) and the Sahara Platform. Although the Atlas system has been erected contemporaneously from Morocco to Algeria and Tunisia during the Middle Eocene to Recent, it displays a conspicuous longitudinal asymmetry, with i) Paleozoic outcrops restricted to its western part; ii) highest elevation occurring in the west, both in the Atlas System and its foreland (Anti-Atlas); iii) low elevation corridors (e.g. Hodna) and depressed foreland (Tunisian Chotts and Sahel area) in the east. We analyse the origin of these striking contrasts in relation with i) the Variscan heritage; ii) crustal vertical movements during the Mesozoic; iii) crustal shortening during the Cenozoic and finally, iv) the occurrence of a Miocene-Quaternary hot mantle anomaly in the west. The Maghreb lithosphere was affected by the Variscan orogeny, and thus thickened only in its western part. During the Late Permian-Triassic, a paleo-high formed in the west between the Central Atlantic and Alpine Tethys rift systems, giving birth to the emergent/poorly subsident West Moroccan Arch. During the late Middle Jurassic-Early Cretaceous, Morocco and western Algeria were dominantly emergent whereas rifting lasted on in eastern Algeria and Tunisia. We ascribe the uplift of the western regions to thermal doming, consistent with the Late Jurassic and Barremian gabbroic magmatism observed there. After the widespread transgression of the high stand Cenomanian-Turonian seas, the inversion of the Atlas System began during the Senonian as a consequence of the Africa-Eurasia convergence. Erosion affected three ENE-trending uplifted areas of NW Africa, which we consider as lithospheric anticlines related to the incipient Africa-Europe convergence. In contrast, in eastern Algeria and Tunisia a NW-trending rift system developed contemporaneously (Sirt rifting), normal to the general trend of the Atlas System. The general inversion and orogenesis of the Atlas System occurred during two distinct episodes, Middle-Late Eocene-Oligocene and Late Miocene-Pliocene, respectively, whereas during the intervening period, the Africa-Europe convergence was mainly accommodated in the Rif-Tell system. Inversion tectonics and crustal thickening may account for the moderate uplift of the eastern Atlas System, not for the high elevation of the western mountain ranges (Middle Atlas, High Atlas, Anti-Atlas). In line with previous authors, we ascribe part of the recent uplift of the latter regions to the occurrence of a NE-trending, high-temperature mantle anomaly, here labelled the Moroccan Hot Line (MHL), which is also marked by a strip of late Miocene-Quaternary alkaline magmatism and significant seismicity.  相似文献   

Implications of climate change in the twenty‐first century for simulated magnitude and frequency of bed‐material transport in tributaries of the Saint‐Lawrence River     

Patrick M. Verhaar  Pascale M. Biron  Robert I. Ferguson  Trevor B. Hoey 《水文研究》2011,25(10):1558-1573

More frequent extreme flood events are likely to occur in many areas in the twenty‐first century due to climate change. The impacts of these changes on sediment transport are examined at the event scale using a 1D morphodynamic model (SEDROUT4‐M) for three tributaries of the Saint‐Lawrence River (Québec, Canada) using daily discharge series generated with a hydrological model (HSAMI) from three global climate models (GCMs). For all tributaries, larger flood events occur in all future scenarios, leading to increases in bed‐material transport rates, number of transport events and number of days in the year where sediment transport occurs. The effective and half‐load discharges increase under all GCM simulations. Differences in flood timing within the tributaries, with a shift of peak annual discharge from the spring towards the winter, compared to the hydrograph of the Saint‐Lawrence River, generate higher sediment transport rates because of increased water surface slope and stream power. Previous research had shown that channel erosion is expected under all GCMs' discharge scenarios. This study shows that, despite lower bed elevations, flood risk is likely to increase as a result of higher flood magnitude, even with falling base level in the Saint‐Lawrence River. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Geomorphologic evidence for Plio‐Quaternary shortening in the southern Neuquén basin (40°S,Argentina)          下载免费PDF全文

Damien Huyghe  Bertrand Nivière  Cédric Bonnel 《地学学报》2015,27(6):426-432

A morphostructural analysis of a Pliocene flood basalt formation in the southern Neuquén basin (40°S) shows evidence of contractional deformation less than 3.5 Ma ago. This formation exhibits a general dip towards the south‐east, with relict outcrops located 100 m higher than the main source volcano, which suggests a local tilting of the lava flow. This tilt has been brought about by Plio‐Quaternary reactivation of the eastern border of the Sañico Massif along two thrusts that offset the lava flow. Another long‐wavelength bulge in the southern part of the lava flow unit indicates a possible Pliocene uplift of the North Patagonian Massif. These results provide new evidence of continuing shortening in the Neuquén basin during the Plio‐Quaternary, challenging the hypothesis that an extensional regime has existed since the end of the Miocene in this basin.  相似文献   

Tropical Pacific mean state and ENSO changes: sensitivity to freshwater flux and remnant ice sheets at 9.5 ka BP     

Yihua Luan  Pascale Braconnot  Yongqiang Yu  Weipeng Zheng 《Climate Dynamics》2015,44(3-4):661-678

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MC‐ICP‐MS Isotope Measurements with Direct Injection Nebulisation (d‐DIHEN): Optimisation and Application to Boron in Seawater and Carbonate Samples     

Pascale Louvat  Julien Bouchez  Guillaume Paris 《Geostandards and Geoanalytical Research》2011,35(1):75-88

We report here an optimisation of the demountable direct injection high efficiency nebuliser (d‐DIHEN) for isotopic measurements with a Neptune (ThermoFisher Scientific, Bremen, Germany) multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS) and describe a method for boron isotopic ratio determination. With direct injection nebulisation 100% of the analyte was introduced into the ICP‐MS plasma and wash times were drastically reduced for elements such as boron and thorium. Compared to the classical stable introduction system (SIS: double Scott/cyclonic spray chamber), sensitivity for boron was 2–5 times higher with d‐DIHEN and wash times up to ten times shorter. Repeatability of ¹¹B/¹⁰B sample‐calibrator bracketing measurements reached 0.25‰ (2s) for seawater and coral samples. Method accuracy and reproducibility were tested on mixed reference solutions having δ¹¹B values in the ranges ?90 to +40‰ and ?2 to +2.5‰, demonstrating our ability to distinguish δ¹¹B values with differences of only 0.25‰. The international seawater reference material NRCC NASS‐5 (National Research Council, Ottawa, Canada), analysed in different sessions over a 10‐month period, yielded an average δ¹¹B value of +39.89 ± 0.25‰, in the upper range of previously published seawater values. A comparison between δ¹¹B determined by d‐DIHEN MC‐ICP‐MS and positive‐TIMS (P‐TIMS) for four modern corals showed an excellent agreement (with bias of less than 0.4‰).  相似文献   

Mid-Holocene and last glacial maximum climate simulations with the IPSL model: part II: model-data comparisons     

Masa Kageyama  Pascale Braconnot  Laurent Bopp  Véronique Mariotti  Tilla Roy  Marie-Noëlle Woillez  Arnaud Caubel  Marie-Alice Foujols  Eric Guilyardi  Myriam Khodri  James Lloyd  Fabien Lombard  Olivier Marti 《Climate Dynamics》2013,40(9-10):2469-2495

The climates of the mid-Holocene (MH, 6,000 years ago) and the Last Glacial Maximum (LGM, 21,000 years ago) have been extensively documented and as such, have become targets for the evaluation of climate models for climate contexts very different from the present. In Part 1 of the present work, we have studied the MH and LGM simulations performed with the last two versions of the IPSL model: IPSL_CM4, run for the PMIP2/CMIP3 (Coupled Model Intercomparion Project) projects and IPSL_CM5A, run for the most recent PMIP3/CMIP5 projets. We have shown that not only are these models different in their simulations of the PI climate, but also in their simulations of the climatic anomalies for the MH and LGM. In the Part 2 of this paper, we first examine whether palaeo-data can help discriminate between the model performances. This is indeed the case for the African monsoon for the MH or for North America south of the Laurentide ice sheet, the South Atlantic or the southern Indian ocean for the LGM. For the LGM, off-line vegetation modelling appears to offer good opportunities to distinguish climate model results because glacial vegetation proves to be very sensitive to even small differences in LGM climate. For other cases such as the LGM North Atlantic or the LGM equatorial Pacific, the large uncertainty on the SST reconstructions, prevents model discrimination. We have examined the use of other proxy-data for model evaluation, which has become possible with the inclusion of the biogeochemistry morel PISCES in the IPSL_CM5A model. We show a broad agreement of the LGM–PI export production changes with reconstructions. These changes are related to the mixed layer depth in most regions and to sea-ice variations in the high latitudes. We have also modelled foraminifer abundances with the FORAMCLIM model and shown that the changes in foraminifer abundance in the equatorial Pacific are mainly forced by changes in SSTs, hence confirming the SST-foraminifer abundance relationship. Yet, this is not the case in all regions in the North Atlantic, where food availability can have a strong impact of foraminifer abundances. Further work will be needed to exhaustively examine the role of factors other than climate in piloting changes in palaeo-indicators.  相似文献   

Relative impacts of insolation changes, meltwater fluxes and ice sheets on African and Asian monsoons during the Holocene     

Charline Marzin  Pascale Braconnot  Masa Kageyama 《Climate Dynamics》2013,41(9-10):2267-2286

In order to better understand the evolution of the Afro-Asian monsoon in the early Holocene, we investigate the impact on boreal summer monsoon characteristics of (1) a freshwater flux in the North Atlantic from the surrounding melting ice sheets and (2) a remnant ice sheet over North America and Europe. Sensitivity experiments run with the IPSL_CM4 model show that both the meltwater flux and the remnant ice sheets induce a cooling of similar amplitude of the North Atlantic leading to a southward shift of the Inter-Tropical Convergence Zone over the tropical Atlantic and to a reduction of the African monsoon. The two perturbations have different impacts in the Asian sector. The meltwater flux results in a weakening of the Indian monsoon and no change in the East Asian monsoon, whereas the remnant ice sheets induce a strengthening of the Indian monsoon and a strong weakening of the East Asian monsoon. Despite the similar coolings in the Atlantic Ocean, the ocean heat transport is reduced only in the meltwater flux experiment, which induces slight differences between the two experiments in the role of the surface latent heat flux in the tropical energetics. In the meltwater experiment, the southward shift of the subtropical jet acts to cool the upper atmosphere over the Tibetan Plateau and hence to weaken the Indian monsoon. In the ice sheet experiment this effect is overwhelmed by the changes in extratropical stationary waves induced by the ice sheets, which are associated with a larger cooling over the Eurasian continent than in the meltwater experiment. However these sensitivity experiments suggest that insolation is the dominant factor explaining the relative changes of the African, Indian and East Asian monsoons from the early to the mid-Holocene.  相似文献   

Book Review: Th. Henning (ed.): Astromineralogy: Lecture Notes in Physics,vol. 609, Edited by ISBN: Springer,New York, 2003, Hardback 291 pages,ISBN: 3-540-44323-1, Price: 66.95 Euro, 62$     

Ehrenfreund  Pascale 《Earth, Moon, and Planets》2003,93(3):236-236

Earth, Moon, and Planets -  相似文献   

Monitoring of UTC(k)’s using PPP and IGS real-time products     

Pascale Defraigne  Wim Aerts  Eric Pottiaux 《GPS Solutions》2015,19(1):165-172

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Neogene tectonostratigraphic history of the southern Neuquén basin (39°–40°30′S,Argentina): implications for foreland basin evolution          下载免费PDF全文

Damien Huyghe  Cédric Bonnel  Bertrand Nivière  Bertrand Fasentieux  Yves Hervouët 《Basin Research》2015,27(5):613-635

Although the Neuquén basin in Argentina forms a key transitional domain between the south‐central Andes and the Patagonian Andes, its Cenozoic history is poorly documented. We focus on the sedimentologic and tectonic evolution of the southern part of this basin, at 39–40°30′S, based on study of 14 sedimentary sections. We provide evidence that this basin underwent alternating erosion and deposition of reworked volcaniclastic material in continental and fluvial settings during the Neogene. In particular, basement uplift of the Sañico Massif, due to Late Miocene–Pliocene intensification of tectonic activity, led to sediment partitioning in the basin. During this interval, sedimentation was restricted to the internal domain and the Collon Cura basin evolved towards an endorheic intermontane basin. From stratigraphic interpretation, this basin remained isolated 7–11 Myr. Nevertheless, ephemeral gateways seem to have existed, because we observe a thin succession downstream of the Sañico Massif contemporaneous with the Collon Cura basin‐fill sequence. Comparisons of stratigraphic, paleoenvironmental and tectonic features of the southern Neuquén basin with other foreland basins of South America allow us to classify it as a broken foreland with the development of an intermontane basin from Late Miocene to Late Pliocene. This implies a thick‐skinned structural style for this basin, with reactivation of basement faults responsible for exhumation of the Sañico Massif. Comparison of several broken forelands of South America allows us to propose two categories of intermontane basins according to their structural setting: subsiding or uplifted basins, which has strong implications on their excavation histories.  相似文献