Understanding distribution and abundance of metals with space and time in estuarine mudflat sedimentary environment

Spatial and depth-wise distribution of sediment components, organic carbon and selected metals (Fe, Mn, Al, Ni, Cr, Co, Zn and Pb) is studied across upper and middle tidal flats from lower and middle estuarine regions of Kundalika Estuary, central west coast of India. Silt and clay form the major components in lower and middle estuary, respectively. Sand, silt, clay and organic carbon showed band-type distribution along the estuary. The sediment deposition over the years took place in varying hydrodynamic conditions in lower and middle estuarine regions. Upper flats of the lower estuary represent mud while middle flats of the lower estuary facilitated the deposition of sandy mud. Correlation results indicated the importance of clay and organic carbon in removal and trapping of metals at lower and middle estuary, respectively. Factor analysis indicated that the distribution of metals is largely controlled by Fe–Mn oxyhydroxides and organic carbon. The middle flats of the lower estuary showed an anthropogenic source for Ni, Cr and Co while middle flats of the middle estuary showed a mainly lithogenic source.     

An Aerosol Model of the Marine and Coastal Atmospheric Surface Layer

We present a microphysical model for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01–100 µm particles. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of ASDF and its dependence on meteorological parameters, height above sea level (H), fetch (X), wind speed (U) and relative humidity (RH), are investigated. At present, the model covers the ranges H = 0–25 m, U?=?3–18 km s^?1, X?≤?120 km and RH?=?40–98%.

The latest version of the Marine Aerosol Extinction Profiles model (MaexPro) is described and applied to the computation and analysis of the spectral profiles of aerosol extinction coefficients α(λ) in the wavelength band λ?=?0.2–12 µm. MaexPro is based on the aforementioned aerosol model assuming spherically shaped aerosol particles and the well-known Mie theory.

The spectral profiles of α(λ) calculated by MaexPro are in good agreement with observational data and the numerical results obtained from the Navy Aerosol Model (NAM) and the Advanced Navy Aerosol Model (ANAM). Moreover, MaexPro was found to be an accurate and reliable tool for investigating the optical properties of atmospheric aerosols.     

Incoherent radiation from relativistic electrons with power energetic spectrum

It is shown that an incoherent high-frequency radiation from an ensemble of relativistic particles with the power energy distribution is described by a certain general expression which covers practically all the cases of particle radiation in random electromagnetic fields of cosmic radiation sources.     

Effect of sampling and linkage on fault length and length–displacement relationship

The power-law exponent (n) in the equation: D=cL ⁿ , with D = maximum displacement and L = fault length, would be affected by deviations of fault trace length. (1) Assuming n=1, numerical simulations on the effect of sampling and linkage on fault length and length–displacement relationship are done in this paper. The results show that: (a) uniform relative deviations, which means all faults within a dataset have the same relative deviation, do not affect the value of n; (b) deviations of the fault length due to unresolved fault tip decrease the values of n and the deviations of n increase with the increasing length deviations; (c) fault linkage and observed dimensions either increase or decrease the value of n depending on the distribution of deviations within a dataset; (d) mixed deviations of the fault lengths are either negative or positive and cause the values of n to either decrease or increase; (e) a dataset combined from two or more datasets with different values of c and orders of magnitude also cause the values of n to deviate. (2) Data including 19 datasets and spanning more than eight orders of fault length magnitudes (10⁻²–10⁵ m) collected from the published literature indicate that the values of n range from 0.55 to 1.5, the average value being 1.0813, and the peak value of n _d (double regression) is 1.0–1.1. Based on above results from the simulations and published data, we propose that the relationship between the maximum displacement and fault length in a single tectonic environment with uniform mechanical properties is linear, and the value of n deviated from 1 is mainly caused by the sampling and linkage effects.     

Petrology of ultramafic and mafic xenoliths in picrite of Kahoolawe Island,Hawaii

A picrite lava (22 wt% MgO; 35 vol.% ol) along the western shore of the1.3–1.4 Ma Kahoolawe tholeiitic shield, Hawaii, contains small xenoliths of harzburgite, lherzolite, norite, and wehrlite. The various rock types have textures where either orthopyroxene, clinopyroxene, or plagioclase is in a poikilitic relationship with olivine. The Mg#s of the olivine, orthopyroxene, and clinopyroxene in this xenolith suite range between 86 and 82; spinel Mg#s range from 60 to 49, and plagioclase is An_75–80. A ⁸⁷Sr/⁸⁶Sr ratio for one ol-norite xenolith is 0.70444. In comparison, the host picrite has olivine phenocrysts with an average Mg# of 86.2 (range 87.5–84.5), and a whole-rock ⁸⁷Sr/⁸⁶Sr ratio of 0.70426. Textural and isotopic information together with mineral compositions indicate that the xenoliths are related to Kahoolawe tholeiitic magmatism, but are not crystallization products of the magma represented by their host picrite. Rather, the xenoliths are crystalline products of earlier primitive liquids (FeO/MgO ranging 1 to 1.3) at 5–9 kbar in the cumulate environment of a magma reservoir or conduit system. The presence of ultramafic xenoliths in picrite but not in typical Kahoolawe tholeiitic lava (6–9 wt% MgO) is consistent with replenishment of reservoirs by dense Mg-rich magma emplaced beneath resident, less dense tholeiitic magma. Mg-rich magmas have proximity to reservoir cumulate zones and are therefore more likely than fractionated residual liquids to entrain fragments of cumulate rock.     

Marine geology in the environs of Bouvet Island and the South Atlantic triple juction

It is suggested that Bouvet Island is the surface manifestation of a mantle plume which has resulted in the creation of a chain of seamounts in the South Atlantic and a general shoaling of the region.The strike of two newly defined large fracture zones borth and south of the Bouvet Island pedestal have been utilized to determine a pole of rotation at 12.5°S, 12.5°W for the Africa-Antarctica motion. A pole at 75°S, 13°E has been calculated for the South America-Antarctica motion. At the triple junction the South America-Africa relative motion is 3.3 cm yr^-1 (whole rate) at 075°. The Africa-Antarctica motion is 1.7 cm yr^-1 at 065° and the South America-Antarctica motion is 1.6 cm yr^-1 at 085.