Relation between n-alkane distributions and effective coalification temperatures in some Permian shales

In Permian shales of the Sydney Basin, Australia, n-alkane distributions have been compared with effective coalification temperatures (ECTs) estimated from vitrinite reflectivities. The upper, non-marine part of the section shows evidence of progressive cracking (shift of n-alkane maximum toward shorter chains and tendency to eliminate longer chains) as depth and ECT increase; but this trend is not maintained in the underlying marine section.All samples show lack of a maximum in the longer-chain n-alkane distribution. Possible reasons discussed are (i) a cracking rate of long chains greater than their formation rate; (ii) a need for higher temperatures than the rock has so far undergone to produce a new crop of long chains; or (iii) exhaustion of the straight-chain generating potential of the kerogen. Pyrolysis experiments may be effective in testing these possibilities.The linking of ECTs to alteration stages of sediment hydrocarbons opens the possibility of comparing these stages among formations which differ in age and organic and inorganic composition, and among basins of diverse geological history.     

Stalagmites from caves in the Bahamas: Indicators of low sea level stand

Presently submerged Bahaman stalagmites can be used to date Pleistocene low sea level stands. Good precision was obtained using both ¹⁴C and ²³⁰Th-/²³⁴U-methods. The respective dates obtained were 21,900 ± 600 and 22,000 ± 350 YBP.     

Trace metal geochemistry of peat under a sanitary landfill-a reconnaissance

Core samples were taken at two sites from a peat deposit buried by a sanitary landfill operated by the city of Vancouver since the 1960s and from a third site where the same peat bed is not covered by landfill. Twenty-nine subsamples from the three cores were analyzed by a variety of techniques to determine the concentration of as many as 34 constituents. The content of heavy metals, the principal object of this investigation, is highest in the lower part of the peat succession, in which there is a significant amount of interbedded inorganic sediment, rather than in the upper clean bog peat. Individual layers as little as 2.5 cm thick can hold concentrations of heavy metals ten times that of the nearby layers. The heavy metal contents show a high positive correlation with those of iron and manganese and a very low correlation with sulfur. Iron from the landfill has been transported by downward percolating groundwater in solution or colloidal suspension into the lower layers of peat deposit where the passing heavy metals were sorbed. A comparison of the amounts of heavy metals stored in the peat alone with the amount leaving the whole landfill annually suggests that some metals, notably lead and arsenic, might be retained in the peat for very long periods, whereas other metals such as zinc and mercury might be quickly lost.     

Arecibo ALFA Array Observations in Search of Lunar Meteoroid-Strike EMPs

Earth, Moon, and Planets - We present the preliminary results of a search for transient Electromagnetic Pulses (EMP) associated with the impact of meteoroids on the lunar surface as observed with...     

Eroding islands of Gulf of Mannar,Southeast India: a consequence of long-term impact of coral mining and climate change

Natural Hazards - Lightning is one of the most widespread and deadly hazards in Bangladesh. Bangladesh has among the highest death rates of any country. The main objective of this study is to...     

Late Pleistocene chronology and environment of the “ice-free corridor” of northwestern Alberta

Pollen and macrofossil analyses of two radiocarbon-dated lake sediment cores in the upper Peace River district were used to investigate the controversial late-glacial geochronology of the “ice-free corridor.” The basal mineral-rich sediments contain reworked, radiogenically “dead” palynomorphs, as well as intrusive “modern” carbon. Analyses of the basal sediments from Boone Lake show that two ¹⁴C ages greater than 12,000 yr B.P. are spuriously old due to contamination by organic matter of Cretaceous age. The data support occlusion or near occlusion of Laurentide and Cordilleran ice in the Peace River area during the late Wisconsinan period. The sediment record began around 12.000 yr B.P. in the ice-dammed and enlarged Boone Lake. An initially open, sedge-dominated cover was invaded by sage, willow, grass, and poplar by 11,700 yr B.P., suggesting that a habitable landscape has existed in the area for at least 12 millennia. The data, however, do not support the ice-free corridor arguments of B. O. K. Reeves (1973, Arctic and Alpine Research5,1–16; 1983, In “Quaternary Coastlines and Marine Archaeology: Towards the Prehistory of Land Bridges and Continental Shelves” (P. M. Masters and N. C. Fleming, Eds.), pp. 389–411. Academic Press. New York), who suggests that ice occlusion did not occur in the Peace River Valley during the last 55,000 yr.     

Three-dimensional carbon dioxide-induced strain distribution within a confined bituminous coal

Sequestration of carbon dioxide in unmineable coal seams is an option to reduce carbon dioxide emissions. It is well known that the interaction of carbon dioxide with unconfined coal induces swelling. This paper contributes three-dimensional strain distribution in confined coal at microstructural level using high-resolution X-ray computerized tomography data and image analysis. Swelling and compression/compaction of regions in the coal matrix occurs with CO₂ uptake. Normal strain varies between ? 1.15% and 0.93%, ? 3.11% and 0.94%, ? 0.43% and 0.30% along x, y and z axes respectively. Volumetric strain varies between ? 4.25% and 1.25%. The positive strains reported are consistent with typical range for unconstrained swelling. However, the average volumetric strains value (? 0.34%) reflect overall volume reduction. Overall swelling is apparently influenced by the confining stresses. The magnitudes of normal strains are heterogeneous and anisotropic. The swelling vs. compression/compaction observed after CO₂ uptake is localized and likely lithotype dependant.     

Satellite/Aerial Image Compression Using Adaptive Block Truncation Coding Technique

Satellite/aerial images taken from high altitude contain large amount of pixels to store accurate information. These high resolution images require large storage capacity and more transmission time. Applying an efficient compression technique on these images can reduce high storage capacity requirement and transmission time. In this paper block truncation coding (BTC) based color image compression technique for aerial/satellite images is proposed. High degree of correlation among the RGB planes of a color image can be reduced by converting these planes into HSV planes. Each of the H and S planes are encoded using BTC with quad clustering and V plane is encoded with BTC based bi-clustering or tri-clustering depending on the edge information present in the plane. The effectivity of the proposed method is validated by comparing it with the conventional BTC and its variant methods. Experimental analysis indicate that the proposed method is superior to other state of the art methods both in terms of visual quality and quantitative metrics.     

r-Process abundance universality and actinide cosmochronology

We review recent observational and theoretical results concerning the presence of actinide nuclei on the surfaces of old halo stars and their use as an age determinant. We present model calculations which show that the observed universality of abundances for 56<Z<75 elements in these stars does not necessarily imply a unique astrophysical site for the r-process. Neither does it imply a universality of abundances of nuclei outside of this range. In particular, we show that a variety of astrophysical r-process models can be constructed which reproduce the same observed universal r-process curve for 56<Z<75 nuclei, yet have vastly different abundances for Z≥75 and possibly Z<56 as well. This introduces an uncertainty into the use of the Th/Eu chronometer as a means to estimate the ages of the metal deficient stars. We do find, however, that the U/Th ratio is a robust chronometer. This is because the initial production ratio of U to Th is almost independent of the astrophysical nucleosynthesis environment. The largest remaining uncertainties in the U/Th initial production ratio are due to the input nuclear physics models.     

RETRACTED ARTICLE: Aspect Sensitivity Considerations in Interpreting Radar Meteor Range-Spread Trail Echo Durations

Earth, Moon, and Planets -