Hasil untuk "Geology"

W. B. Harland, A. Cox, R. Armstrong

J. Veizer, J. Veizer, F. Mackenzie

M. Taner, F. Koehler, R. Sheriff

R. Horton

R. Schmidt, K. Housen

Robert F. Butler

P. Coney, D. Jones, J. Monger

P. A. Ziegler

N. Price, J. Cosgrove

J. O. Amaefule, M. Altunbay, D. Tiab et al.

R. Galbraith, G. Laslett

B. Burchfiel, Zhiliang Chen, K. Hodges et al.

G. Partyka, J. Gridley, John A. Lopez

V. Cloutier, R. Lefebvre, R. Therrien et al.

Weidong Sun, Xing Ding, Yanhua Hu et al.

Tianfu Xu, E. Sonnenthal, N. Spycher et al.

YAN Xusheng1, 2 , WANG Qiong1, 2 , SU Wei1, 2, YE Weimin1, 2, ZHANG Fengshou1, 2, LIU Yichun1, 2

To investigate the swelling properties and microstructure evolution of compacted bentonite in an annular technological void under different temperatures, swelling pressure tests are conducted on compacted bentonite in an annular technological void. After technological void is closed, water content, dry density and microstructures is determined, respectively. Results show that the swelling pressure time-history curve shows a single-peak pattern, initially rising to the peak before falling and stabilizing. The dynamic equilibrium of the "wedge" force, formed by the thickening of bound water film, laminar cleavage, pore collapse and thickening of diffusion double layers, dominates the force states from the vertical lateral limit to the constant volume. Higher temperatures intensify the increase water content and decrease dry density from the interior to the exterior. The swelling behavior is enhanced by the increase in montmorillonite expansive coefficient and water molecule diffusive coefficient with temperature, leading to more inter-assemblage pores being occupied by the swollen matrix. At higher temperatures, more water molecules entered the interlayers, causing higher hydration reactions, lamellar cleavage, and pore collapse, which reduced the total void ratio and enhanced the swelling properties.

Yanyan Chen, C. Zou, M. Mastalerz et al.

Fourier transform infrared spectroscopy (FTIR) can provide crucial information on the molecular structure of organic and inorganic components and has been used extensively for chemical characterization of geological samples in the past few decades. In this paper, recent applications of FTIR in the geological sciences are reviewed. Particularly, its use in the characterization of geochemistry and thermal maturation of organic matter in coal and shale is addressed. These investigations demonstrate that the employment of high-resolution micro-FTIR imaging enables visualization and mapping of the distributions of organic matter and minerals on a micrometer scale in geological samples, and promotes an advanced understanding of heterogeneity of organic rich coal and shale. Additionally, micro-FTIR is particularly suitable for in situ, non-destructive characterization of minute microfossils, small fluid and melt inclusions within crystals, and volatiles in glasses and minerals. This technique can also assist in the chemotaxonomic classification of macrofossils such as plant fossils. These features, barely accessible with other analytical techniques, may provide fundamental information on paleoclimate, depositional environment, and the evolution of geological (e.g., volcanic and magmatic) systems.

M. V. Rodkin, M. Yu. Andreeva

The task was set on investigation of the possibility of constructing a new algorithm for earthquake prediction based on a set of precursor effects that had been reliably identified from the world data as a result of constructing the generalized vicinity of a strong earthquake from a scaled combination of the data on a large number of foreshock and aftershock areas of individual strong earthquakes. In relation to the Kamchatka-Northern Kurils region, the first-stage solution of this task lies in clarification of the regional character of the averaged precursor effects on the basis of the most complete and homogeneous regional catalogue. There has been a later onset of anomalous changes in the intensity of flow of events and in the slope of the recurrence diagram for intermediate-depth earthquakes. The deep-seated earthquakes show a dominant trend of increased rather than decreased depth of weak events in the vicinity of strong events. The specified features of the averaged precursor behavior will be used as typical patterns to predict different-depth earthquakes in the Kuril-Kamchatka region.

Boivin Simon, Lathuilière Bernard, Martini Rossana

Each new coral-bearing outcrop found in Lower Jurassic strata is useful to understand the evolution of corals between the end-Triassic mass extinction and the Toarcian anoxic event. Here we provide new taxonomic data on corals issued from fieldwork on four outcrops from the region of Amellagou, in the High Atlas Mountains, Morocco. A set of 157 coral specimens have been collected from a small biostrome, a giant reef and two olistholiths, spanning from Hettangian − Sinemurian time interval to early Pliensbachian. These corals are distributed in 14 families, 22 genera and 27 species. Among these species, two are new: Lepidophyllia (Heterastraea) microcalix sp. nov., represented enough to allow a population study and Paracuifia castellum sp. nov. The study extends the last appearance datum of several genera known only in the Triassic till now, namely: Parastraeomorpha, Araiophyllum, Paracuifia, Pinacophyllum and, possibly, Paravolzeia. For this reason, the severity of the end-Triassic mass extinction is questioned in comparison to the extinction events that happened around the Pliensbachian-Toarcian boundary. For this reason, moreover, the phyletic discontinuity between some Triassic and Jurassic taxa is also addressed. Some Lazarus taxa known from Triassic and Pliensbachian remain absent in Hettangian and now, at a lesser degree, in Sinemurian. That is why we assume that the absence of these taxa is only due to the poor preservation of coral environments during these times. This study also changes our view on the first appearance datum of several genera that were known in Jurassic strata, namely: Proleptophyllia, Vallimeandropsis and, possibly, Lochmaeosmilia. A special attention is given to the distribution of colonial arrangements and points to the important proportion of cerioid and solitary corals. Additionally, the study highlights the existence of significant proportions of thamnasterioid and meandroid forms. The presence of corals with such a level of integration, together with the occurrence of two species that show platy to ramose transition in their colony shape, namely Hispaniastraea murciana and Chrondrocoenia clavellata, stresses the effectiveness of a photosymbiosis in these Early Jurassic coral communities. Lastly, the proportion of solitary specimens increased over time, revealing the uniqueness of coral assemblages during the Pliensbachian.