First Lunar Flashes Observed from Morocco (ILIAD Network): Implications for Lunar Seismology     

Mamoun Ait Moulay Larbi  Ahmed Daassou  David Baratoux  Sylvain Bouley  Zouhair Benkhaldoun  Mohamed Lazrek  Raphael Garcia  Francois Colas 《Earth, Moon, and Planets》2015,115(1-4):1-21

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Seismic stratigraphical record of Lake Levinson‐Lessing,Taymyr Peninsula: evidence for ice‐sheet dynamics and lake‐level fluctuations since the Early Weichselian     

Elodie Lebas  Sebastian Krastel  Bernd Wagner  Raphael Gromig  Grigory Fedorov  Marlene Baumer  Natalia Kostromina  Haflidi Haflidason 《Boreas: An International Journal of Quaternary Research》2019,48(2):470-487

A multi‐channel, high‐resolution seismic reflection survey using a Micro‐GI airgun was carried out in the framework of the Russian‐German project PLOT (Paleolimnological Transect) on Lake Levinson‐Lessing, Taymyr Peninsula, in 2016. In total, ~70 km of seismic reflection profiles revealed in unprecedented detail the glacial and postglacial sedimentary infill of the lake basin. Five main seismic units have been recognized and interpreted as glacial (Unit V), subglacial and proglacial (Unit IV), marine (Unit III), fluvial‐lacustrine (Unit II) and lacustrine (Unit I) sediments. Of particular significance are imbricated, south‐orientated structures present in the southernmost part of the lake basin within Unit V and a large topographic ridge recognized in front of those structures. We interpret these structures as push moraines and an end moraine, respectively, left by the glacier after its retreat. The depositional pattern of the units above the moraines documents past lake‐level fluctuations. We interpret Unit IV, Unit III and Unit I as highstand deposits, and Unit II as lowstand deposits. Gas‐charged sediments dominate the northern part of the lake basin, whilst they occur only sporadically and in limited spatial extent in the central and southern parts of the lake. In the latter areas, the seismic and echo‐sounder data suggest recent tectonic activity. Our study contributes to the reconstruction of environmental conditions in the Taymyr Peninsula directly following the Early Weichselian deglaciation and shows that deep tectonic lake basins affected by several glaciations can preserve important palaeoenvironmental records, which contributes significantly to our understanding of palaeoenvironmental changes in the Taymyr Peninsula and the central Russian Arctic.  相似文献   

Deglaciation history of Lake Ladoga (northwestern Russia) based on varved sediments     

Raphael Gromig  Bernd Wagner  Volker Wennrich  Grigory Fedorov  Larisa Savelieva  Elodie  Lebas  Sebastian Krastel  Dominik Brill  Andrei Andreev  Dmitry Subetto  Martin Melles 《Boreas: An International Journal of Quaternary Research》2019,48(2):330-348

Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP, when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP, older than previously assumed. Varve sedimentation covers the Bølling/Allerød interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselkä II moraine north of Lake Ladoga, by c. 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c. 9.5 cal. ka BP, characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c. 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c. 4.5 cal. ka BP until present.  相似文献   

OSL chronology of Lynch's Crater,the longest terrestrial record in NE-Australia     

Uwe Rieser  Raphael A.J. Wüst 《Quaternary Geochronology》2010,5(2-3):233-236

Lynch's Crater on the Atherton Tablelands in NE-Australia formed about 230,000 years ago during an explosive eruption, creating a maar more than 80 m deep. Since the eruption, the maar has been filled with lake sediments that are topped by peat material. A 64 m long core was recovered and an OSL dating project was undertaken to extend the chronology beyond 16 m depth, which according to ¹⁴C age control represents ～60 ka. The predominantly organic lake sediments contained abundant fine quartz of aeolian origin, and the Single Aliquot Regenerative Method (SAR) provided satisfactory equivalent dose (D_E) estimates. However, the determination of the dose rate proved both critical and difficult. Extremely low radionuclide contents led to cosmic radiation being the dominant dose rate contribution for most samples. The OSL chronology presented in this paper thus relies on modelling the changing cover by sediments and lake water over the burial time.  相似文献   

Challenges of modeling current very large lahars at Nevado del Huila Volcano,Colombia     

Raphael Worni  Christian Huggel  M. Stoffel  B. Pulgarín 《Bulletin of Volcanology》2012,74(2):309-324

Nevado del Huila, a glacier-covered volcano in the South of Colombia’s Cordillera Central, had not experienced any historical eruptions before 2007. In 2007 and 2008, the volcano erupted with phreatic and phreatomagmatic events which produced lahars with flow volumes of up to about 300 million m³ causing severe damage to infrastructure and loss of lives. The magnitude of these lahars and the prevailing potential for similar or even larger events, poses significant hazards to local people and makes appropriate modeling a real challenge. In this study, we analyze the recent lahars to better understand the main processes and then model possible scenarios for future events. We used lahar inundation depths, travel duration, and flow deposits to constrain the dimensions of the 2007 event and applied LAHARZ and FLO-2D for lahar modeling. Measured hydrographs, geophone seismic sensor data and calculated peak discharges served as input data for the reconstruction of flow hydrographs and for calibration of the models. For model validation, results were compared with field data collected along the Páez and Simbola Rivers. Based on the results of the 2007 lahar simulation, we modeled lahar scenarios with volumes between 300 million and 1 billion m³. The approach presented here represents a feasible solution for modeling high-magnitude flows like lahars and allows an assessment of potential future events and related consequences for population centers downstream of Nevado del Huila.  相似文献   

IGNORANCE – AND LEARNING     

Raphael G. Kazmann 《Ground water》2012,50(2):168-169

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Components of rainy seasons’ variability in Equatorial East Africa: onset, cessation, rainfall frequency and intensity   总被引：1，自引：0，他引：1  

Pierre Camberlin  Vincent Moron  Raphael Okoola  Nathalie Philippon  Wilson Gitau 《Theoretical and Applied Climatology》2009,98(3-4):237-249

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The Transfiguration continental red-bed Cu–Pb–Zn–Ag deposit,Quebec Appalachians,Canada     

Alexandre Raphael Cabral  Georges Beaudoin  Bruce E. Taylor 《Mineralium Deposita》2009,44(3):285-301

The Transfiguration Cu–Pb–Zn–Ag deposit, enclosed within reduced grey sandstone, is associated with continental red beds of the Lower Silurian Robitaille Formation in the Quebec Appalachians, Canada. The Robitaille Formation rests unconformably on foliated Cambro-Ordovician rocks. The unconformity is locally cut by barite veins. The basal unit of the Robitaille Formation comprises green wacke and pebble conglomerate, which locally contain calcite nodules. The latter have microstructures characteristic of alpha-type calcretes, such as “floating” fabrics, calcite-filled fractures (crystallaria) and circumgranular cracks. Massive, grey sandstone overlies the basal green wacke and pebble conglomerate unit, which is overlain, in turn, by red, fine-grained sandstone. Mineralisation occurred underneath the red sandstone unit, chiefly in the grey sandstone unit, as disseminated and veinlet sulphides. Chalcopyrite, the most abundant Cu sulphide, replaced early pyrite. Calcrete, disseminated carbonate and vein carbonate have stable isotope ratios varying from −7.5‰ to −1.1‰ δ¹³C and from 14.7‰ to 21.3‰ δ¹⁸O. The negative δ¹³C values indicate the oxidation of organic matter in a continental environment. Sulphur isotope ratios for pyrite, chalcopyrite and galena vary from −19‰ to 25‰ δ³⁴S, as measured on mineral concentrates by a conventional SO₂ technique. Laser-assisted microanalyses (by fluorination) of S isotopes in pyrite show an analogous range in δ³⁴S values, from −21‰ to 25‰. Negative and positive δ³⁴S values are compatible with bacterial sulphate reduction (BSR) in systems open and closed with respect to sulphate. We interpret similarly high δ³⁴S values for sulphide concentrates (25.1‰) and for vein barite (26.2‰) to result from rapid and complete thermochemical reduction of pore-water sulphate. Two early to late diagenetic stages of mineralisation best explain the origin of the Transfiguration deposit. The first stage was characterised by the ponding of groundwater over the Taconian unconformity, recorded by calcrete and early pyrite formation via BSR in grey sandstone. Early pyrite contains up to 2 wt.% Pb, which is consistent with Pb fixation by sulphate-reducing bacteria. The second stage (II) is defined by the replacement of early pyrite by chalcopyrite, as well as by sulphide precipitation via either BSR or thermochemical sulphate reduction (TSR) in grey sandstone. This event resulted from the synsedimentary fault-controlled percolation and mixing of (1) an oxidising, sulphate-bearing cupriferous fluid migrating per descensum from the red-bed sequence and (2) a hydrocarbon-bearing fluid migrating per ascensum from the Cambro-Ordovician basement. Mixing between the two fluids led to sulphate reduction, causing Cu sulphide precipitation. The positive correlation between Cu and Fe³⁺/Fe²⁺ bulk rock values suggests that Fe acted as a redox agent during sulphate reduction. Stage II diagenetic fluid migration is tentatively attributed to the Late Silurian Salinic extensional event.  相似文献   

Geochemistry of Some Marine Fe–Mn Nodules and Crusts with Respect to Pt Contents     

Alexandre Raphael Cabral  Carl‐Diedrich Sattler  Bernd Lehmann  Harilaos Tsikos 《Resource Geology》2009,59(4):400-406

Bulk chemical analyses for Pt and Pd in marine Fe–Mn nodules and crusts from different provenances are presented, together with a wide range of elements. Platinum contents vary from 70–328 ppb, whereas Pd contents extend from 0.6–4.7 ppb only. Bromine and Pb show strong positive correlations with Pt. Lead is remarkably enriched in Fe–Mn precipitates over seawater, but Br is a conservative‐type element in seawater and shows no enrichment in Fe–Mn precipitates. Hence, the Pt–Br–Pb element association combines two elements, Br and Pb, of extremely contrasting enrichment factors in Fe–Mn precipitates.  相似文献   

When will it end? Long-lived intracontinental reactivation in central Australia     

Raphael Quentin de Gromard  Christopher L.Kirkland  Heather M.Howard  Michael T.D.Wingate  Fred Jourdan  Brent I.A.Mc Innes  Martin Daniík  Noreen J.Evans  Bradley J.McDonald  R.Hugh Smithies 《地学前缘(英文版)》2019,10(1):149-164

The post-Mesoproterozoic tectonometamorphic history of the Musgrave Province, central Australia, has previously been solely attributed to intracontinental compressional deformation during the 580 -520 Ma Petermann Orogeny. However, our new structurally controlled multi-mineral geochronology results,from two north-trending transects, indicate protracted reactivation of the Australian continental interior over ca. 715 million years. The earliest events are identified in the hinterland of the orogen along the western transect. The first tectonothermal event, at ca. 715 Ma, is indicated by40 Ar/39 Ar muscovite and U e Pb titanite ages. Another previously unrecognised tectonometamorphic event is dated at ca. 630 Ma by Ue Pb analyses of metamorphic zircon rims. This event was followed by continuous cooling and exhumation of the hinterland and core of the orogen along numerous faults, including the Woodroffe Thrust,from ca. 625 Ma to 565 Ma as indicated by muscovite, biotite, and hornblende40 Ar/39 Ar cooling ages. We therefore propose that the Petermann Orogeny commenced as early as ca. 630 Ma. Along the eastern transect,40 Ar/39 Ar muscovite and zircon(Ue Th)/He data indicate exhumation of the foreland fold and thrust system to shallow crustal levels between ca. 550 Ma and 520 Ma, while the core of the orogen was undergoing exhumation to mid-crustal levels and cooling below 600-660℃. Subsequent cooling to 150 -220℃ of the core of the orogen occurred between ca. 480 Ma and 400 Ma(zircon [Ue Th]/He data)during reactivation of the Woodroffe Thrust, coincident with the 450 -300 Ma Alice Springs Orogeny.Exhumation of the footwall of the Woodroffe Thrust to shallow depths occurred at ca. 200 Ma. More recent tectonic activity is also evident as on the 21 May, 2016(Sydney date), a magnitude 6.1 earthquake occurred, and the resolved focal mechanism indicates that compressive stress and exhumation along the Woodroffe Thrust is continuing to the present day. Overall, these results demonstrate repeated amagmatic reactivation of the continental interior of Australia for ca. 715 million years, including at least 600 million years of reactivation along the Woodroffe Thrust alone. Estimated cooling rates agree with previously reported rates and suggest slow cooling of 0.9 -7.0℃/Ma in the core of the Petermann Orogen between ca. 570 Ma and 400 Ma. The long-lived, amagmatic, intracontinental reactivation of central Australia is a remarkable example of stress transmission, strain localization and cratonization-hindering processes that highlights the complexity of Continental Tectonics with regards to the rigid-plate paradigm of Plate Tectonics.  相似文献