Predicting landslide sliding distance based on energy dissipation and mass point kinematics

Natural Hazards - Based on classical mechanics and the law of energy conservation, we present a model for predicting landslide sliding distance. We conceptualize landslide movement as the movement...     

Biostratigraphy and depositional facies of the Cretaceous-Tertiary boundary strata in Amakusa-Shimojima,Kyushu, Western Japan

The Upper Himenoura Subgroup exposed in the island of Amakusa-Shimojima, Kyushu, Japan shows an example of the terminal Cretaceous stratigraphic record in the circum Pacific region. This sequence is a part of the Upper Cretaceous intra-arc basins of southwest Japan. Four cycles of upward coarse-graded facies are recognized. Each cycle consists of a basinal mud facies in the lower part and a tide-dominated shallow marine to brackish coarse clastic facies in the upper part. Biostratigraphic correlation chiefly based on ammonites, inocerami and trigoniids indicates that this sequence is Campanian to Maastrichtian in age. The occurrence of the above three fossils decreases upward and is terminated at the top of the sequence, being replaced by a molluscan assemblage similar to the Danian. This suggests that the sedimentation may have continued to the very end of the Cretaceous period and possibly to the beginning of the Tertiary.     

Using amphibole phenocrysts to track vapor transfer during magma crystallization and transport: An example from Mount St. Helens,Washington

In order to evaluate and further constrain models for volatile movement and vapor enrichment of magma stored at shallow levels, amphibole phenocrysts from 2004–2005 Mount St. Helens dacite were analyzed for major and selected trace elements (Li, Cu, Zn, Mn, and REE) and Li isotopes. Several recent studies have examined fluid-mobile trace element abundances in phencryst phases and melt inclusions as a means of tracking volatile movement within subvolcanic magmatic systems, and high Li contents in plagioclase phenocrysts from 1980 and 2004 Mount St. Helens dacites have been interpreted as evidence that shallow magma was fluxed by a Li-bearing vapor phase prior to eruption.     

Ocean tide loading (OTL) displacements from global and local grids: comparisons to GPS estimates over the shelf of Brittany, France

In this paper we examine OTL displacements detected by GPS stations of a dedicated campaign and validate ocean tide models. Our area of study is the continental shelf of Brittany and Cotentin in France. Brittany is one of the few places in the world where tides provoke loading displacements of ∼10–12 cm vertically and a few cm horizontally. Ocean tide models suffer from important discrepancies in this region. Seven global and regional ocean tide models were tested: FES2004 corrected for K2, TPXO.7.0, TPXO.6.2, GOT00.2, CSR4.0, NAO.99b and the most recent regional grids of the North East Atlantic (NEA2004). These gridded amplitudes and phases of ocean tides were convolved in order to get the predicted OTL displacements using two different algorithms. Data over a period of 3.5 months of 8 GPS campaign stations located on the north coast of Brittany are used, in order to evaluate the geographical distribution of the OTL effect. We have modified and implemented new algorithms in our GPS software, GINS 7.1. GPS OTL constituents are estimated based on 1-day batch solutions. We compare the observed GPS OTL constituents of M₂, S₂, N₂ and K₁ waves with the selected ocean tide models on global and regional grids. Large phase-lag and amplitude discrepancies over 20° and 1.5 cm in the vertical direction in the semi-diurnal band of M₂ between predictions and GPS/models are detected in the Bay of Mont St-Michel. From a least squares spectral analysis of the GPS time-series, significant harmonic peaks in the integer multiples of the orbital periods of the GPS satellites are observed, indicating the existence of multipath effects in the GPS OTL constituents. The GPS OTL observations agree best with FES2004, NEA2004, GOT00.2 and CSR4.0 tide models.     

Singularity and Nonnormality in the Classification of Compositional Data

Geologists may want to classify compositional data and express the classification as a map. Regionalized classification is a tool that can be used for this purpose, but it incorporates discriminant analysis, which requires the computation and inversion of a covariance matrix. Covariance matrices of compositional data always will be singular (noninvertible) because of the unit-sum constraint. Fortunately, discriminant analyses can be calculated using a pseudo-inverse of the singular covariance matrix; this is done automatically by some statistical packages such as SAS. Granulometric data from the Darss Sill region of the Baltic Sea is used to explore how the pseudo-inversion procedure influences discriminant analysis results, comparing the algorithm used by SAS to the more conventional Moore–Penrose algorithm. Logratio transforms have been recommended to overcome problems associated with analysis of compositional data, including singularity. A regionalized classification of the Darss Sill data after logratio transformation is different only slightly from one based on raw granulometric data, suggesting that closure problems do not influence severely regionalized classification of compositional data.     

Crystal features of supergene gold at Hannan South,Western Australia

Deep weathering of basalt-hosted sulphidic gold mineralisation has resulted in remobilisation of the gold and the formation of a supergene deposit. The deposit occurs beneath an ephemeral lake system and is at least partially saturated by highly saline groundwater. A general downward movement of an iron redox front associated with the weathering has controlled the distribution of the gold and its morphology. It is unusual in that the high fineness gold crystals formed are coarse and well-preserved. Small octahedra, up to 50 μm, are the most abundant form of gold crystals but large, up to 3 mm, octahedral plates are common. Crystal morphology variations described here suggest that the gold is initially precipitated as euhedral octahedra and plates. Subsequent dissolution and recrystallisation associated with fluctuations in the chemical environment above the redox front has led to the development of the more common irregular dendritic or wire gold forms observed in other supergene deposits.     

Characterization of groundwater chemistry under the influence of lithologic and anthropogenic factors along a climatic gradient in Upper Cauvery basin, South India

Hydrogeological and climatic effect on chemical behavior of groundwater along a climatic gradient is studied along a river basin. ‘Semi-arid’ (500–800 mm of mean annual rainfall), ‘sub-humid’ (800–1,200 mm/year) and ‘humid’ (1,200–1,500 mm/year) are the climatic zones chosen along the granito-gneissic plains of Kabini basin in South India for the present analysis. Data on groundwater chemistry is initially checked for its quality using NICB ratio (<±5 %), EC versus TZ+ (~0.85 correlation), EC versus TDS and EC versus TH analysis. Groundwater in the three climatic zones is ‘hard’ to ‘very hard’ in terms of Ca–Mg hardness. Polluted wells are identified (>40 % of pollution) and eliminated for the characterization. Piper’s diagram with mean concentrations indicates the evolution of CaNaHCO₃ (semi-arid) from CaHCO₃ (humid zone) along the climatic gradient. Carbonates dominate other anions and strong acids exceeded weak acids in the region. Mule Hole SEW, an experimental watershed in sub-humid zone, is characterized initially using hydrogeochemistry and is observed to be a replica of entire sub-humid zone (with 25 wells). Extension of the studies for the entire basin (120 wells) showed a chemical gradient along the climatic gradient with sub-humid zone bridging semi-arid and humid zones. Ca/Na molar ratio varies by more than 100 times from semi-arid to humid zones. Semi-arid zone is more silicaceous than sub-humid while humid zone is more carbonaceous (Ca/Cl ~14). Along the climatic gradient, groundwater is undersaturated (humid), saturated (sub-humid) and slightly supersaturated (semi-arid) with calcite and dolomite. Concentration–depth profiles are in support of the geological stratification i.e., ~18 m of saprolite and ~25 m of fracture rock with parent gneiss beneath. All the wells are classified into four groups based on groundwater fluctuations and further into ‘deep’ and ‘shallow’ based on the depth to groundwater. Higher the fluctuations, larger is its impact on groundwater chemistry. Actual seasonal patterns are identified using ‘recharge–discharge’ concept based on rainfall intensity instead of traditional monsoon–non-monsoon concept. Non-pumped wells have low Na/Cl and Ca/Cl ratios in recharge period than in discharge period (Dilution). Few other wells, which are subjected to pumping, still exhibit dilution chemistry though water level fluctuations are high due to annual recharge. Other wells which do not receive sufficient rainfall and are constantly pumped showed high concentrations in recharge period rather than in discharge period (Anti-dilution). In summary, recharge–discharge concept demarcates the pumped wells from natural deep wells thus, characterizing the basin.