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21.
This paper deals with a new occurrence of sedimentary natroalunite (Na, K) Al3, (SO4)2 (OH)6, in the caprock of a diapir of middle Miocene evaporites from the Gemsa peninsula, located on the southwestern coast of the Gulf of Suez. Field observations, petrographic examinations and stable isotope (18O, 34S) measurements on the associated authigenic phases of anhydrite and native sulphur argue for the genesis of natroalunite at a rather high temperature (i.e. higher than 75°C) by the reaction of clay minerals with sulphuric acid. The sulphuric acid was produced by the concatenation of the following reactions which are thought to increase the diagenetic temperature: bacterial reduction of sulphate evaporites, and oxidation of hydrogen sulphide to native sulphur and sulphate where aerated conditions prevailed in the pore fluids. These changes through time from reducing to oxidizing diagenetic conditions were controlled by the progressive uplift of the diapiric system toward the land surface so that the draining ground waters became progressively oxygenated. 相似文献
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Increasing pressure on the tropical environment requires a more thorough understanding of hydrological processes as part of reconciling the conflicting demands of economic development vis-à-vis sustainable land management. Using TOPMODEL, a physically based semi-distributed topohydrological model, we test its validity in modelling the stream flow dynamics (hydrograph) in a 1 ha tropical rainforest catchment in French Guiana. Another objective is through field validation of TOPMODEL to ascertain possible runoff generation mechanisms. The field validation of the temporal and spatial hydrodynamics across a rainfall–runoff event reveals that TOPMODEL may be suited for applications to this particular tropical rainforest environment; in fact, this is possibly the first successful application of such a model within the humid tropics. The main reasons why the model was successful are the presumed low hydraulic conductivities of the subsoil, coupled with the absence of an additional deep groundwater body, the contribution from which has caused difficulties in application of topographically, ‘physically’ based runoff models elsewhere in the humid tropics. © 1997 John Wiley & Sons, Ltd. 相似文献
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STEVE KERSHAW SYLVIE CRASQUIN MARIE‐BÉATRICE FOREL CARINE RANDON PIERRE‐YVES COLLIN ERDAL KOSUN SYLVAIN RICHOZ AYMON BAUD 《Sedimentology》2011,58(3):739-755
The Permian–Triassic Boundary sequence at Çürük Dag, near Antalya, Turkey, begins with a major erosion surface interpreted as being the Late Permian lowstand, on which lies ca 0·4 m of grainstone/packstone composed of ooids, peloids and bioclasts. Most ooids are superficial coats on fragments of calcite crystals presumed to be eroded from crystal fans which are no longer present. The erosion surface is smooth and shows no evidence of dissolution; the grainstone/packstone contains intraclasts of the underlying wackestone, proving erosion. Next are 15 m of microbialite comprised of interbedded stromatolites, thrombolites, plus beds of planar limestones with small‐scale erosion. The latter comprise a complex interlayering of stromatolitic, thrombolitic and peloidal fabrics and precipitated crystal fans, which form a hybrid of microbialite and inorganic carbonate, together with bioclastic debris and micrite. The Çürük Dag microbialite sequence is repetitious; the lower part is more complex, with abundant stromatolites and hybrid microbialites. Some of the stromatolites are themselves hybrids composed of peloids and crystal fans. In the upper part of the sequence stromatolites are missing and the rock is composed mostly of recrystallized thrombolites that develop upwards from tabular to domal form. The domes form directly below small breaks in microbialite growth where very thin shelly micrites and grainstones/packstones are deposited. Repetition of facies may be controlled by sea‐level change; a deepening‐up model is consistent with the evidence. Stromatolites (with abundant crystal fans) dominate in shallower water, deepening through hybrid microbialite and interlayered sediments to thrombolite, probably no more than a few tens of metres deep, followed by breaks and renewal of microbialite growth. An interpretation of open marine fully oxygenated waters for microbialite growth is consistent with ongoing parallel work that has identified Bairdioid ostracods in the microbialite, a group known to be open marine. However, other researchers have proposed low oxygen conditions for Permian–Triassic boundary facies globally, so work continues to confirm whether the Çürük Dag microbialite grew in dysoxic or normally oxygenated conditions. The principal stimulus for post‐extinction microbialites is likely to be carbonate supersaturation of the oceans. The microbialite sequence is overlain by a further 25 m of grainstone/packstone (without microbialite), followed by Early Triassic shales. Overall, microbialites form a thin aggradational sequence during an overall relative sea‐level rise, consistent with global eustatic rise following the Late Permian lowstand. 相似文献
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PIERRE F. SOLOMON J. CORNILLEAU-WEHRLIN N. CANU P. SCIME E. E. BALOGH A. FORSYTH R. J. 《Solar physics》1997,172(1-2):327-334
We present a study of whistler-mode wave generation and wave particle interaction in the vicinity of interplanetary shocks as observed by the Ulysses spacecraft. Generally the whistler-mode waves (measured in the frequency range 0.22–448 Hz) are observed downstream of the shocks where they persist for some hours. From the electron distribution functions (EDF) in the energy range 1.6 to 862 eV measured by the spacecraft, we compute the wave growth rate of the electromagnetic electron cyclotron and Landau instabilities for the case of oblique propagation of the waves with respect to the interplanetary magnetic field (IMF) B. In general, in agreement with the wave measurements, the instability grows mostly downstream of the shock fronts. Following the wave activity, velocity space diffusion of the electrons results in a marginally stable state with some sporadic fluctuations. 相似文献
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PIERRE LASALLE WILLIAM W. SHILTS 《Boreas: An International Journal of Quaternary Research》1993,22(1):25-37
Occurrences of Balanus hameri-bearing diamicts described in this paper and pertinent ( Balanus plates and pelecypods shells) 14 C dates suggest that there was glacial activity in the Champlain Sea basin between 11,000 BP and 10,400 BP and that this activity can be ascribed to a climatic cooling episode correlative with the Younger Dryas of the late-glacial sequence of northeastern Europe. 相似文献
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JEAN‐JACQUES CORNÉE JEAN‐LÈN LÉTICÉE PHILIPPE MÜNCH FRÉDÉRIC QUILLÉVÉRÉ JEAN‐FRÉDÉRIC LEBRUN PIERRE MOISSETTE JUAN‐CARLOS BRAGA MIHAELA MELINTE‐DOBRINESCU LYVANE DE MIN JULIEN OUDET AURAN RANDRIANASOLO 《Sedimentology》2012,59(5):1426-1451
Pliocene and Pleistocene deposits from Grande‐Terre (Guadeloupe archipelago, French Lesser Antilles) provide a remarkable example of an isolated carbonate system built in an active margin setting, with sedimentation controlled by both rapid sea‐level changes and tectonic movements. Based on new field, sedimentological and palaeontological analyses, these deposits have been organized into four sedimentary sequences (S1 to S4) separated by three subaerial erosion surfaces (SB0, SB1 and SB2). Sequences S1 and S2 (‘Calcaires inférieurs à rhodolithes’) deposited during the Late Zanclean to Early Gelasian (planktonic foraminiferal Zones PL2 to PL5) in low subsidence conditions, on a distally steepened ramp dipping eastward. Red algal‐rich deposits, which dominate the western part of Grande‐Terre, change to planktonic foraminifer‐rich deposits eastward. Vertical movements of tens of metres were responsible for the formation of SB0 and SB1. Sequence S3 (‘Formation volcano‐sédimentaire’, ‘Calcaires supérieurs à rhodolithes’ and ‘Calcaires à Agaricia’) was deposited during the Late Piacenzian to Early Calabrian (Zones PL5 to PT1a) on a distally steepened, red algal‐dominated ramp that changes upward into a homoclinal, coral‐dominated ramp. Deposition of Sequence S3 occurred during a eustatic cycle in quiet tectonic conditions. Its uppermost boundary, the major erosion surface SB2, is related to the Cala1 eustatic sea‐level fall. Finally, Sequence S4 (‘Calcaires à Acropora’) probably formed during the Calabrian, developing as a coral‐dominated platform during a eustatic cycle in quiet tectonic conditions. The final emergence of the island could then have occurred in Late Calabrian times. 相似文献
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Seismic evidence of up to 200 m lake‐level change in Southern Patagonia since Marine Isotope Stage 4
ANDREA CATALINA GEBHARDT CHRISTIAN OHLENDORF FRANK NIESSEN MARC DE BATIST FLAVIO S. ANSELMETTI DANIEL ARIZTEGUI PIERRE KLIEM STEFAN WASTEGÅRD BERND ZOLITSCHKA 《Sedimentology》2012,59(3):1087-1100
Maar lake Laguna Potrok Aike is located north of the Strait of Magellan (south‐eastern Patagonia). Seismic reflection profiles revealed a highly dynamic palaeoclimate history. Dunes were identified in the eastern part of the lake at approximately 30 to 80 m below the lake floor, overlying older lacustrine strata, and suggest that the region experienced dry conditions probably combined with strong westerly winds. It is quite likely that this can be linked to a major dust event recorded in the Antarctic ice cores during Marine Isotope Stage 4. The dunes are overlain by a series of palaeo‐shorelines indicating a stepwise water‐level evolution of a new lake established after this dry period, and thus a change towards wetter conditions. After the initial, rapid and stepwise lake‐level rise, the basin became deeper and wider, and sediments deposited on the lake shoulder at approximately 33 m below present‐day lake level point towards a long period of lake‐level highstand between roughly 53·5 ka cal. bp and 30 ka cal. bp with a maximum lake level some 200 m higher than the desiccation horizon. This highstand was then followed by a regressional phase of uncertain age, although it must have happened some time between approximately 30 ka cal. bp and 6750 yrs cal. bp . Dryer conditions during the Mid‐Holocene are evidenced by a dropping lake level, resulting in a basin‐wide erosional unconformity on the lake shoulder. A second stepwise transgression between ca 5·8 to 5·4 ka cal. bp and ca 4·7 to 4 ka cal. bp with palaeo‐shorelines deposited on the lake shoulder unconformity again indicates a change towards wetter conditions. 相似文献
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Does the invisible hand have a green thumb? Incentives, linkages, and the creation of wealth out of industrial waste in Victorian England 总被引:1,自引:0,他引:1
PIERRE DESROCHERS 《The Geographical journal》2009,175(1):3-16
'Loop closing', that is, the creation of waste recycling linkages between different industries, has been hailed as a means of simultaneously achieving improved economic and environmental performance. As a result of the widespread assumption that traditional market incentives and institutions are not conducive to such an outcome, however, there remains a fair amount of scepticism as to what the capacity of business self-interest to promote this behaviour actually is. This article challenges the dominant negative perspective by discussing by-product development in one of the most market-oriented societies in human history, Victorian England. Building on nineteenth and early twentieth century writings on the topic, as well as a more detailed analysis of the development of valuable by-products from highly problematic iron and coal gas production residuals, a case is made that the search for increased profitability within the context of private property rights often simultaneously promoted economic and environmental progress in the long run, as well as on different geographical scales. 相似文献