Modeling long-period noise in kinematic GPS applications

We develop and test an algorithm for modeling and removing elevation error in kinematic GPS trajectories in the context of a kinematic GPS survey of the salar de Uyuni, Bolivia. Noise in the kinematic trajectory ranges over 15 cm and is highly autocorrelated, resulting in significant contamination of the topographic signal. We solve for a noise model using crossover differences at trajectory intersections as constraints in a least-squares inversion. Validation of the model using multiple realizations of synthetic/simulated noise shows an average decrease in root-mean-square-error (RMSE) by a factor of four. Applying the model to data from the salar de Uyuni survey, we find that crossover differences drop by a factor of eight (from an RMSE of 5.6 to 0.7 cm), and previously obscured topographic features are revealed in a plan view of the corrected trajectory. We believe that this algorithm can be successfully adapted to other survey methods that employ kinematic GPS for positioning.     

Tonian Tectonic-Strata Regions and their Geological Significance in China

The continent of China developed through the coalescence of three major cratons(North China, Tarim and Yangtze) and continental micro-blocks through the processes of oceanic crust disappearance and acceretionary-collision of continental crusts. The strata of the Chinese continental landmass are subdivided into 12 tectonic-strata regions. Based on the composition of geological features among the three main cratons, continental micro-blocks and other major global cratons, their affinities can be preliminarily deduced during the Tonian period, using evidence from sedimentary successions, paleobiogeography, tectonic and magmatic events. The Yangtze and Tarim cratons show that they have close affinities during the assembly-dispersal milestone of the Rodinia Supercontinent. The sedimentary record and magmatic age populations in the blocks suggest that there was a widespread, intensive magmatic event that resulted from a subduction process during ～1000–820 Ma, related to continental rifting around the Yangtze and Tarim cratons. However, they differ greatly from the North China Craton. The continental micro-blocks in the Panthalassic Ocean could have some missing connection with the North China Craton that persisted until the Middle-Late Devonian. In contrast, the Alxa Block showed a strong affinity with the Tarim Craton. The revised Tonian paleogeography of the Rodinia Supercontinent is a good demonstration of how to show the relationship between the main cratons and the continental micro-blocks.     

The Variance of Mango‘s Light—Hydrocarbon Parameter K

The analyses of light hydrocarbons in oils from the Tarim Basin show that the Mango‘s parameter K is about unity except those oils trapped in the eastern part of the Tazhong (Central Tarim)Fault Uplift,The regular variance of K may indicates the accumulation and admixture of the oil populations in the eastern part of the Tazhong Fault Uplift.     

The relationship between total dissolved carbon dioxide and its stable carbon isotope ratio in aquatic sediments

A model is constructed to predict the stable carbon isotope ratio of the total dissolved CO₂ in aquatic sediments and laboratory reactors. The major parameters of the model are the fractionation between CO₂ and CH₄ as well as the intra-molecular fractionation of acetate, the relative production of CH₄ from CO₂ reduction versus acetate fermentation, the net production ratio of CO₂ to CH₄ and the stable carbon isotope ratio of the source organic carbon. The model is fitted to published data and to date from the littoral sediments of Lake Memphremagog, Quebec, Canada. The inclusion of the intra-molecular fractionation factor of acetate in the model provides a good fit to the data; without this factor, the values of the other parameters necessary for a good fit appear unreasonable.     

Unburned coal as a source of hydrocarbons in surface sediments

The isolation and quantification of the various sources of trace levels of hydrocarbons in environmental samples is a difficult analytical task. Based on the hydrocarbon concentrations found in non-polluted surface sediment and an estimate of the amounts of coal particles found in similar areas we conclude that unburned coal can be a significant source of sediment hydrocarbons in the coastal marine environment.     

Electron paramagnetic resonance spectroscopy: A suggested approach to trace metal analysis in marine environments

Electron paramagnetic resonance (EPR) spectroscopy analysis of marine samples from different environments appears to differentiate between adsorbed and structural Mn (II) and Fe (III) sites in the sediment. This suggests that EPR may provide a means of distinguishing different environmental influences on sediment. Acid extract solutions from sediment samples exhibit clearly defined EPR spectra due to Mn(II), Ti(III), Fe(III), and VO(IV), which are amenable to qualitative and quantitative analysis at concentrations below one part per million. Spectra of several shellfish vary considerably, both between species, and within a species, depending on sampling localities. Resonances from Mn(II), Mo(V), and Fe(III) can be obtained. Mn(II) is substituted for Ca(II) in the calcite structure of some shells. The low detection limits, small sample size, required and identification of oxidation states by EPR complement other analytical techniques and may prove useful in marine systems.     

Model systems for anatexis of pelitic rocks

Subsolidus and melting reactions involving calcic plagioclase in pelitic assemblages in the K-Na-Ca model system occur at higher temperatures than their K-Na counterparts. For the most calcic plagioclase compositions observed in high-grade pelitic rocks (An₂₅-An₄₀) the equilibria are rarely extended by more than 30 ° C above those in KA1O₂-NaAlO₂-Al₂O₃-SiO₂-H₂O, although all discontinuities in facies inferred for the K-Na system are continuously displaced when they involve Ca-bearing plagioclase. The maximum pressure-temperature overlap between muscovite dehydration and initial melting reactions occurs in the pressure range of 4–6 kbar between about 640 ° and 720 ° C. This provides optimum conditions for anatectic melt generation in felsic rocks of the appropriate compositions progressively metamorphosed in kyanite-sillimanite facies series. Progressive regional metamorphism at pressures of 2–4 kbar, corresponding to andalusite-sillimanite facies series, shows little overlap between muscovite dehydration and initial melting reactions. Consequently anatectic melt generation in andalusite-sillimanite facies series would require the participation of biotite in dehydration-melting reactions. Felsic intrusive rock in andalusite-sillimanite terranes could have risen upward from their anatectic sites in high grade kyanite-sillimanite facies series at depth. Many andalusite-sillimanite facies series terranes culminating in migmatites could represent upward movement of kyanite-sillimanite facies series rocks to shallower depths with uplift rates faster than cooling rates.     

Freshwater reserves of mid-atlantic coast barrier Islands

A multiple regression model was constructed for the purpose of predicting barrier island hydrology from easily measureable island characteristics. The model was developed using data obtained from 17 sites on the Outer Banks of North Carolina. The accuracy of the model for predicting key hydrologic variables was evaluated by statistical and graphic procedures. In general, agreement between observed and predicted values of the hydrologic variables was very good, suggesting that the quantity of potable water at various island sites can be estimated without resorting to extensive field investigations. The model was then applied to Assateague Island, a barrier island located off the coasts of Maryland and Virginia. Results indicate that the original model developed for the Outer Banks may be applied to other barrier islands but that errors involved may necessitate corrections in detailed studies. Correction for bias in predictions for Assateague was shown to be possible with limited field data from surface resistivity surveys.     

Pu and137Cs in coastal sediments

Analyses are presented of¹³⁷Cs,²³⁸Pu, and^239,240Pu, in relation to depth in sediment, in 21 gravity cores. These cores span the ranges of times 1964–1975, and of water depths 12–2000 m; they come from three distinct sedimentation areas off the northeast coast of the United States. Although the ranges of total sediment inventories of^239,240Pu and of¹³⁷Cs from the various areas hardly overlap, the range of ratios of the inventories of these two nuclides is probably the same in all the areas. In the shallow-water cores the^239,240Pu/¹³⁷Cs ratio regularly diminishes with depth in the core, and a tendency is seen for curves of this function to have similar slopes in each area; ratios of²³⁸Pu/^239,240Pu show no change with depth in these shallow-water cores. In the deeper-water cores, the^239,240Pu/¹³⁷Cs ratio shows no systematic change with depth, but sometimes the²³⁸Pu/^239,240Pu ratio shows a minimum at the sediment surface, and is much higher deeper in the cores. We believe that these phenomena can be explained in terms of a complicated bioturbational process moving the nuclides, together, down into the sediments, of chemical resolubilization, at depth, of plutonium only, and of its subsequent upward translocation in the interstitial solution. Some re-immobilization of plutonium near the sediment surface is implied, and a mechanism is suggested for this, based on displacement of plutonium from organic complexes by the increasing concentrations, in upper layers of the sediment, of re-oxidized dissolved iron.