Agents of low temperature ocean crust alteration     

Hubert Staudigel  Karlis Muehlenbachs  Stephen H. Richardson  Stanley R. Hart 《Contributions to Mineralogy and Petrology》1981,77(2):150-157

¹⁸O and⁸⁷Sr/⁸⁶Sr isotopic data from smectites, calcites, and whole rocks, together with published isotopic age determinations, alkali element concentration data and petrographic observations suggest a sequential model of ocean floor alteration. The early stage lasts about 3 m.y. and is characterized by palagonite and smectite formation, and solutions with a large basaltic component, increasing with temperature which varies from 15° to 80° C at DSDP site 418A. Most carbonates are depositedafter this stage from solutions with a negligible basaltic Sr component and temperatures of 15° to 40° C. Water of seawater Sr and O isotopic composition is shown to percolate to at least 500 m into the basaltic basement. No evidence was found for continuing exchange of strontium or oxygen after 3 m.y.Lamont-Doherty Geological Observatory Contribution number 3199  相似文献   

Das Problem des hypothetischen „Pazifischen Kontinentes“ gesehen von der chilenischen Pazifikküste     

Priv.-Doz. Dr. Hubert Miller 《International Journal of Earth Sciences》1970,59(3):927-938

Zusammenfassung Die verbreitet in den Pazifik hinausweisenden Strukturlinien der prämesozoischen Orogene Chiles fordern die ehemalige Existenz sialischer Kruste jenseits der heutigen Küste an Stellen, wo derzeit nur dünne, simatische Kruste vorhanden ist. Fünf Möglichkeiten des Verschwindens dieser kontinentalen Kruste werden diskutiert. Aus der ruhigen Lagerung der känozoischen Sedimente vor der heutigen Küste wird geschlossen, daß der wesentliche Teil der Umwandlung von kontinentaler Kruste in ozeanische seit längerer Zeit beendet ist.

---

From the structural trends of the pre-Mesozoic orogenes pointing toward the Pacific, the existence of a former sialic (continental) crust, then beyond the modern coast of Chile, may be inferred. This inference applies in places where at present only a thin simatic crust is encountered. Five modes of disappearance of this sialic (continental) crust are discussed. The rather undisturbed position of the Cenozoic sediments off the present coast indicates that the main transformation of continental crust in oceanic crust has stopped some time ago.

---

Résumé Les directions structurales des anciens orogènes exigent l'existence d'une écorce sialique au-delà de la côte actuelle du Chili, à des endroits où il ne se trouve à present qu'une mince croûte simatique. Dans le present article cinq explications pour la disparition de cette écorce continentale sont discutées. La position peu disloquée des sediments cénozoiques, au-delà de la côte actuelle, montre que la partie essentielle de la transformation de la croûte continentale en une crôute océanique est terminée depuis longtemps.

---

- , - . . , , .

  相似文献   

Unravelling the microfacies signatures of parasequences using computer-optimized similarity matrices     

Guy H. Spence  Annie Arnaud-Vanneau†  Hubert Arnaud†  Maurice E. Tucker‡ 《Sedimentology》2004,51(6):1243-1271

The microfacies of a Lower Cretaceous carbonate drillcore from Oman are characterized using optimizing matrices of Jaccard's similarity coefficients of community. Other than systems tract boundaries, there is no obvious evidence of individual parasequences in the core. However, diagnostic patterns in microfossil distribution identify environmental gradients recording changes in water depth. These gradients are used to define individual parasequences, parasequence sets, stacking patterns and key surfaces. The patterns suggest that deposition was controlled by successive fourth‐ to fifth‐order (high‐frequency) relative sea‐level cycles superimposed on an underlying third‐order relative sea‐level rise. Although the correlation of these depositional subunits to systematic changes in water depth and the rate of carbonate accumulation alone is not incontrovertible proof of such a sea‐level control, concurrent multiorder relative sea‐level cyclicity provides by far the most likely explanation. A microfacies deposited when the water depth was shallowing is characterized by a relay of microfossils with affinities that shallow upwards. Conversely, a microfacies that records a gradual increase in water depth has a relay of microfossils with affinities that deepen upwards. Microfacies characterized by an assemblage of microfossils with similar affinities record deposition when the benthic environmental conditions remained stable, either because of an equilibrium between shallow water carbonate deposition and rising sea level, or in deeper water where sediment composition was relatively insensitive to changes of water depth. Microfacies characterized by mixed affinity assemblages record syndepositional reworking. During periods of embedded multiorder sea‐level changes, individual parasequences within systems tracts are shown to record more complex environmental gradients than simply the repetition of successive shallowing‐up units as traditionally represented in carbonate sequence stratigraphic models. The microfacies of an individual parasequence may shallow up, or may record both deepening‐up and shallowing‐up depositional phases, as well as periods of sedimentation when benthic environments remained stable. Individual parasequence boundaries may be submarine or subaerial unconformities, or be conformable, as part of a predictable stratigraphic pattern related to the temporal position of an individual parasequence within the underlying third‐order cycle of relative sea‐level change. The hitherto ubiquitous use of assemblages to describe carbonate microfacies, coupled with the widespread use of the metre‐scale shallowing‐up template to identify parasequences, may have led to such complexities previously being overlooked.  相似文献   

Effect of eutrophication on species composition and growth of freshwater mussels(Mollusca,Unionidae) in Lake Hallwil (Aargau,Switzerland)     

Hubert E. Arter 《Aquatic Sciences - Research Across Boundaries》1989,51(2):87-99

Species composition, relative abundance and life history of unionid mussels are compared between 1982–86 and 1915–19 in Lake Hallwil and the outflowing brook. The recent samples of unionid mussels were collected by divers, whereas the older ones were from a shell collection. The motivation for the comparison was that the trophic degree of the lake has changed since the beginning of the century from mesotrophic to highly eutrophic. The effects of this increased trophic degree of the lake on the life cycle of unionid mussels is discussed. Predictions are made about species composition and life history in the context of the ongoing lake restoration by the authorities.  相似文献   

Le passage Ordovicien–Silurien et la partie inférieure du Silurien (Sud-Est du Massif armoricain, France)The Ordovician–Silurian transition and the lower part of the Silurian (southeastern Armorican Massif, France)     

Jos Manuel Piarra  Michel Robardet  Ahmed Bourahrouh  Florentin Paris  Zlia Pereira  Jean Le Menn  Rmy Gourvennec  Toms Oliveira  Hubert Lardeux 《Comptes Rendus Geoscience》2002,334(16)

A new section in the Silurian graptolitic ‘phtanites’ (black cherts) of Les Fresnaies at Chalonnes-sur-Loire (SE Armorican Massif) shows for the first time that these rocks (1) succeed conformably to Uppermost Ordovician (Hirnantian) glaciomarine deposits and (2) contain successive graptolite assemblages that characterise the base of the Silurian, the whole Rhuddanian and Aeronian stages and the lower part of the Telychian. To cite this article: J.M. Piçarra et al., C. R. Geoscience 334 (2002) 1177–1183.  相似文献   

The segmentation procedure as a tool for discrete modeling of hydrometeorological regimes   总被引：1，自引：1，他引：0  

P. Hubert 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(4-5):297-304

  相似文献   

Ecohydrological modelling with EcH2O‐iso to quantify forest and grassland effects on water partitioning and flux ages     

Audrey Douinot  Doerthe Tetzlaff  Marco Maneta  Sylvain Kuppel  Hubert Schulte‐Bisping  Chris Soulsby 《水文研究》2019,33(16):2174-2191

We used the new process‐based, tracer‐aided ecohydrological model EcH₂O‐iso to assess the effects of vegetation cover on water balance partitioning and associated flux ages under temperate deciduous beech forest (F) and grassland (G) at an intensively monitored site in Northern Germany. Unique, multicriteria calibration, based on measured components of energy balance, hydrological function and biomass accumulation, resulted in good simulations reproducing measured soil surface temperatures, soil water content, transpiration, and biomass production. Model results showed the forest “used” more water than the grassland; of 620 mm average annual precipitation, losses were higher through interception (29% under F, 16% for G) and combined soil evaporation and transpiration (59% F, 47% G). Consequently, groundwater (GW) recharge was enhanced under grassland at 37% (~225 mm) of precipitation compared with 12% (~73 mm) for forest. The model tracked the ages of water in different storage compartments and associated fluxes. In shallow soil horizons, the average ages of soil water fluxes and evaporation were similar in both plots (~1.5 months), though transpiration and GW recharge were older under forest (~6 months compared with ~3 months for transpiration, and ~12 months compared with ~10 months for GW). Flux tracking using measured chloride data as a conservative tracer provided independent support for the modelling results, though highlighted effects of uncertainties in forest partitioning of evaporation and transpiration. By tracking storage—flux—age interactions under different land covers, EcH₂O‐iso could quantify the effects of vegetation on water partitioning and age distributions. Given the likelihood of drier, warmer summers, such models can help assess the implications of land use for water resource availability to inform debates over building landscape resilience to climate change. Better conceptualization of soil water mixing processes and improved calibration data on leaf area index and root distribution appear obvious respective modelling and data needs for improved simulations.  相似文献