Reconstruction of paleocoastlines for the northwestern South China Sea since the Last Glacial Maximum

The range of relative sea level rise in the northwestern South China Sea since the Last Glacial Maximum was over 100 m. As a result, lowland regions including the Northeast Vietnam coast, Beibu Gulf, and South China coast experienced an evolution from land to sea. Based on the principle of reconstructing paleogeography and using recent digital elevation model, relative sea level curves, and sediment accumulation data, this paper presents a series of paleogeographic scenarios back to 20 cal. ka BP for the northwestern South China Sea. The scenarios demonstrate the entire process of coastline changes for the area of interest. During the late glacial period from 20 to 15 cal. ka BP, coastline slowly retreated, causing a land loss of only 1×10⁴ km², and thus the land-sea distribution remained nearly unchanged. Later in 15–10 cal. ka BP coastline rapidly retreated and area of land loss was up to 24×10⁴km², causing lowlands around Northeast Vietnam and South China soon to be underwater. Coastline retreat continued quite rapidly during the early Holocene. From 10 to 6 cal. ka BP land area had decreased by 9×10⁴km², and during that process the Qiongzhou Strait completely opened up. Since the mid Holocene, main controls on coastline change are from vertical crustal movements and sedimentation. Transgression was surpassed by regression, resulting in a land accretion of about 10×10⁴km². Supported by Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences (Grant No. MSGL0711), the Guangdong Natural Science Foundation (Grant No. 04001309) and Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences (Grant No. MGE2007KG04)     

Quantitatively distinguishing sediments from the Yangtze River and the Yellow River using δ Eu<Subscript>N</Subscript>-ΣREEs plot

Sediment samples were collected from the lower channel of the Yangtze River and the Yellow River and the contents of rare earth elements (REEs) were measured. In addition, some historical REEs data were collected from published literatures. Based on the δ Eu_N-ΣREEs plot, a clear boundary was found between the sediments from the two rivers. The boundary can be described as an orthogonal polynomial equation by ordinary linear regression with sediments from the Yangtze River located above the curve and sediments from the Yellow River located below the curve. To validate this method, the REEs contents of sediments collected from the estuaries of the Yangtze River and the Yellow River were measured. In addition, the REEs data of sediment Core 255 from the Yangtze River and Core YA01 from the Yellow River were collected. Results show that the samples from the Yangtze River estuary and Core 255 almost are above the curve and most samples from the Yellow River estuary and Core YA01 are below the curve in the δEu_N-ΣREEs plot. The plot and the regression equation can be used to distinguish sediments from the Yangtze River and the Yellow River intuitively and quantitatively, and to trace the sediment provenance of the eastern seas of China. The difference between the sediments from two rivers in the δEu_N-ΣREEs plot is caused by different mineral compositions and regional climate patterns of the source areas. The relationship between δEu_N and ΣREEs is changed little during the transport from the source area to the river, and from river to the sea. Thus the original information on mineral compositions and climate of the source area was preserved. Supported by National Natural Science Foundation of China (Grant Nos. 40506016, 40576032, and 90411014)     

Conditional nonlinear optimal perturbation: Applications to stability,sensitivity, and predictability

Conditional nonlinear optimal perturbation (CNOP) is a nonlinear generalization of linear singular vector (LSV) and features the largest nonlinear evolution at prediction time for the initial perturbations in a given constraint. It was proposed initially for predicting the limitation of predictability of weather or climate. Then CNOP has been applied to the studies of the problems related to predictability for weather and climate. In this paper, we focus on reviewing the recent advances of CNOP’s applications, which involves the ones of CNOP in problems of ENSO amplitude asymmetry, block onset, and the sensitivity analysis of ecosystem and ocean’s circulations, etc. Especially, CNOP has been primarily used to construct the initial perturbation fields of ensemble forecasting, and to determine the sensitive area of target observation for precipitations. These works extend CNOP’s applications to investigating the nonlinear dynamical behaviors of atmospheric or oceanic systems, even a coupled system, and studying the problem of the transition between the equilibrium states. These contributions not only attack the particular physical problems, but also show the superiority of CNOP to LSV in revealing the effect of nonlinear physical processes. Consequently, CNOP represents the optimal precursors for a weather or climate event; in predictability studies, CNOP stands for the initial error that has the largest negative effect on prediction; and in sensitivity analysis, CNOP is the most unstable (sensitive) mode. In multi-equilibrium state regime, CNOP is the initial perturbation that induces the transition between equilibriums most probably. Furthermore, CNOP has been used to construct ensemble perturbation fields in ensemble forecast studies and to identify sensitive area of target observation. CNOP theory has become more and more substantial. It is expected that CNOP also serves to improve the predictability of the realistic predictions for weather and climate events plays an increasingly important role in exploring the nonlinear dynamics of atmospheric, oceanic and coupled atmosphere-ocean system. Supported by National Basic Research Program of China (Grant Nos. 2006CB403606, 2007CB411800), National Natural Science Foundation of China (Grant Nos. 40830955, 40675030, 40505013), Institute of Atmospheric Physics, Chinese Academy of Sciences (Grant No. IAP07202), and LASG State Key Laboratory Special Fund     

The metallogenic mechanism of the sandstone-type copper deposits in the Chuxiong Basin,Yunnan Province

The sandstone-type Cu deposits in the Chuxiong Basin occur in the Cretaceous Gaofengsi Formation and the Maotoushan Formation and the orebodies are stratoid and lenticular in form, structurally controlled by their stratigraphical position. Ore structures are dominated by impregnated and striped ones. In addition, it has been observed that copper mineralization is controlled by water-discharge and deformation structures. Orebodies are commonly seen on the gently inclined limbs of the anticline, with the involution front. Copper mineralization shows a distinct zonation. S, Pb isotope and REE data suggest that the copper would stem from the country rocks and the sulfur largely from the lower strata. During diagenesis oxidized Cu-bearing brines derived from the upper parts and reduced brines from the lower parts are involved in metallogenetic reactions in the stress neutral plane, which is the key to the formation of copper deposits in the Chuxiong Basin.     

Fossil carotenoids and paleolimnology of meromictic Mahoney Lake,British Columbia,Canada

Vertical distribution of fossil carotenoids in a sediment core from meromictic Mahoney Lake was studied. Besides okenone and demethylated okenone, lutein and zeaxanthin and-carotene isomers were identified. No carotenoids typical for purple nonsulfur or green sulfur bacteria were detected. The ratio of zeaxanthin to lutein (above 1:1 in all samples) indicates a dominance of cyanobacteria over green algae in the phytoplankton assemblages of the past. Okenone, which is found exclusively in Chromatiaceae, was the dominating carotenoid in all sediment zones.The oldest sediment layers containing okenone were deposited 11 000 years ago. Between 9000 and 7000 and since 3000 years b.p., Chromatiaceae reached a considerable biomass in the lake. Vertical changes in okenone concentration were not related to changes of paleotemperatures. In contrast, okenone concentrations decreased during periods of volcanic ash input. During most of the lake history, however, mean okenone concentrations were positively correlated with sedimentation rates. This indicates that vertical changes of okenone concentration in the sediment reflect past changes of purple sulfur bacterial biomass in the lake.According to these results, the past limnology of Mahoney Lake resembled that of the present with a sulfide-containing monimolimnion and a well-developed population of okenone-bearing purple sulfur bacteria.     

From subduction to transform motion: a seabeam survey of the Hellenic trench system

Preliminary results of a multi-narrow beam survey of the Hellenic trench system, in the Eastern Mediterranean, are presented. The southwestern Ionian branch is divided in small basins, partly filled with Pleistocene sediments. The morphology suggests that the basins are deformed by a compressional stress acting roughly perpendicularly to the trench along N50°E. This direction is the direction of the regional slip vector of the shallow thrust-type earthquakes. The structure of the southeastern Pliny-Strabo branch is quite different. Narrow en-e´chelon slots, oriented N40°E, have been mapped within the main troughs oriented N60°E. The regional earthquake slip vector is also oriented along N40°E. We conclude that the Hellenic trench system is an active subduction system, dominated by thrust along the Ionian branch and by transform motion along the Pliny-Strabo branch.     

Basical characteristics of fluid geologic process of interlayer oxidation zone sandstone-type uranium deposit

This paper reveals the physicochemical properties such as component, formulation, genesis, tem-perature, pH, Eh, salinity and pressure of all main alteration fluid of interlayer oxidation zone sand-stone-type uranium deposits after studying the geologic process and geochemistry of internal typical sandstone-type uranium deposits such as Shihongtan deposit in the Turpan-Hami basin, 512 deposit in the Yili basin, Dongsheng deposit in the Ordos basin. The composition of fluid can be divided into two parts based on the analysis of inclusion: one can be affirmed as atmospheric water with ordinary temperature epigenesist according to the character of hydrogen and oxygen isotope of inclusion, the other is natural gas containing gaseous hydrocarbon like CH₄, and CO₂ as well as a little H₂S, CO, H₂, N₂ and so on, it always contains a small quantity of hydrocarbon liquid in petroliferous basins. The fluid property of oxidation alteration zone is always oxidation alkaline, and neutrality or weak acid-weak alkaline and reducibility during the metallizing process, but at secondary reduction or deoxidization zone it becomes strong reduction alkaline. Oxygenic groundwater in the fluid is the activate and mig-ratory medium of uranium element, but the gaseous hydrocarbon like CH₄ as well as H₂, H₂S, CO from natural gas is the important sedimentary reducer of uranium mineral; the transformation of pH,Eh in fluid environment is the main reason for the formation of uranium metallization.     

Coal facies evolution of the main minable coal-bed in the Heidaigou Mine,Jungar Coalfield,Inner Mongolia,northern China

The No. 6 Coal-bed from the Heidaigou Mine, Jungar Coalfield, Inner Mongolia is a super-large Ga deposit. The dominant carrier of Ga is boehmite in coal. The study of coal facies may provide genetic enrichment information of Ga and its carrier (boehmite) in the Ga deposit. On the basis of study on coal petrology and mineralogy, it was found that the No. 6 Coal-bed from the Heidaigou Mine of Jungar was enriched in inertinites and the microlitho-types were dominated by clarodurite. The maceral morphological features and association indicate that the coal-bed was formed in a dry sedimentary environment or in a periodic dry sedimentary environment caused by the alternating variations of groundwater level. The optimum conditions for the enrichment of Ga and its particular carrier (boehmite) were dominated by four transitional conditions: (1) the upper delta plain which was the transitional zone between alluvial and lower delta plains, (2) the transitional zone between the dry and wet forest swamps, being slightly apt to the dry one, (3) the transitional tree density between the thick and loose ones, and (4) the low moor that was the transitional zone between two high moors during peat accumulation.     

A New Approach for Border Detection of the Dumluca (Turkey) Iron Ore Area: Wavelet Cellular Neural Networks

Anomaly analysis is used for various geophysics applications such as determination of geophysical structure's location and border detections. Besides the classical geophysical techniques, artificial intelligence based image processing algorithms have been found attractive for geophysical anomaly analysis. Recently, cellular neural networks (CNN) have been applied to geophysical data and satisfactory results are reported. CNN provides fast and parallel computational capability for geophysical image processing applications due to its filtering structure. The behavior of CNN is defined by two template matrices that are adjusted by a properly supervised learning algorithm. After training stage for geophysical data, Bouguer anomaly maps can be processed and analyzed sequentially. In this paper, CNN learning and processing capability have been improved, combining Wavelet functions and backpropagation learning algorithms. The new architecture is denoted as Wavelet-Cellular Neural networks (Wave-CNN) and it is employed to analyze Bouguer anomaly maps which are important to extract useful information in geophysics. At first, Wave-CNN performance is tested on synthetic geophysical data, which are created by a computer environment. Then, Bouguer anomaly maps of the Dumluca iron ore field have been analyzed and results are reported in comparison to real drilling results.