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Pan X.,Zhejiang University | Pan X.,Australian National University | Pan X.,Zhejiang Institute of Hydrogeology and Engineering Geology | Shen Z.,Zhejiang University | And 3 more authors.

Magma flow directions for 6 Late Cretaceous mafic dyke swarms exposed in coastal southeastern China (SE China) were analyzed using anisotropy of magnetic susceptibility (AMS) and field evidence. Normal AMS fabrics are predominant. The AMS of the dyke swarms originates mainly from the distribution anisotropy of intersertal magnetite that crystallized during late stage magma flow or after the magma cooled. The AMS fabrics record tectonic stress combined with magma flow. Sub-vertical to vertical magma flow is inferred from symmetrical imbricated magnetic foliations of dyke walls and field evidence for 5 dyke swarms. The inferred (sub-) vertical flow directions also indicate that the magma chambers were probably just beneath the sampled locations. Low anisotropy degree, different orientations of principal AMS axes, and asymmetrical magnetic foliations of normal fabrics oblique to dyke walls indicate syntectonic emplacement of the Late Cretaceous dyke swarms under an extensional tectonic regime caused by Paleo-Pacific plate subduction. © 2014 Elsevier B.V. Source

Wang Y.,CAS Nanjing Institute of Geography and Limnology | Long H.,CAS Nanjing Institute of Geography and Limnology | Yi L.,Chinese Academy of Sciences | Yang L.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | And 2 more authors.
Quaternary Geochronology

Sedimentary records from the inner-shelf of the East China Sea (ECS) are unique for the reconstruction of post-glacial palaeoclimate and sea-level changes. So far, the chronology of sediment succession from this region has mainly been based on radiocarbon dating, which might be problematic due to reworked deposition or old carbon contamination. In this study we tested the applicability of optically stimulated luminescence (OSL) dating to a drilling core (ECS-DZ1) taken from the northern ESC. A total of 20 OSL samples and two radiocarbon samples were collected from the upper 58m of this core. The results indicate the likely sufficient reset of OSL signal of fine-grained (4-11μm) quartz before burial, and thus reliable chronology for the studied core sediments. For one sample, however, the extracted coarse-grained (100-200μm) quartz overestimated the deposition age significantly, presumably resulting from partial bleaching prior to deposition. The fine-grained quartz ages are generally consistent with the stratigraphical order, and the reliability of these OSL ages are further validated by two selective robust 14C dates. The chronological framework of core ECS-DZ1 reveals striking sedimentation-rate changes. By comparison with other chronostratigraphical records, we infer that post-glacial deposition history (since ~15 ka) of the study site is likely related to regional sea-level rise and delta-estuary environment evolution, as well as strengthened human activities and/or coastal currents. © 2015 Elsevier B.V. Source

Yi L.,CAS Institute of Geology and Geophysics | Yi L.,Chinese Academy of Sciences | Ye X.,Zhejiang Institute of Hydrogeology and Engineering Geology | Chen J.,Zhejiang Institute of Hydrogeology and Engineering Geology | And 6 more authors.
Quaternary International

Owing to the large and increasing population density in low-lying coastal regions, even small changes in sea level can have substantial societal and economic impacts. Alternations of terrestrial and marine sediments deposited in coastal areas or continental shelves are important and effective indicators of sea-level changes, and thus, have been widely studied in the marginal seas of China over the past 30 years. However, sea-level change results from not only eustatic factors but also tectonic activity. The Zhe-Min (or Zhejiang-Fujian) Uplift (ZMU) was such an important factor in geomorphology, and formed a barrier preventing entry of sea water into the northern marginal seas of China, but its Quaternary history is poorly known. In this study, a new borehole (ECS-DZ1) was drilled in the Zhoushan Islands, northern East China Sea to obtain information on the evolution of the ZMU during the Quaternary. Information from paleomagnetic and luminescence dating was combined with data on sedimentary changes. The main results are: (1) constrained by luminescence ages, the upper sedimentary units were extrapolated to have been deposited since ~0.2 Ma; (2) paleomagnetic results suggest that the ECS-DZ1 borehole sequence spans from the pre-Olduvai Matuyama reverse chron to the Brunhes normal chron, approximately constraining the age of the basal sedimentary unit to ~2.0 Ma; (3) a significant hiatus or erosion between two major sedimentary units possibly occurred between the late Early Pleistocene and Middle Pleistocene. As the Zhoushan Islands are within the ZMU and considering previous transgression studies around this region, it is inferred that the ZMU subsided at ~2.0 Ma, allowing sea water to invade northward in the Yellow Sea basin. The ZMU might have been uplifted again no later than 1.0Ma, causing a sedimentary hiatus or lacustrine development. After ~0.2 Ma, the ZMU subsided completely, allowing large transgressions to develop across the northern marginal seas of China in the context of global sea-level changes. © 2014 Elsevier Ltd and INQUA. Source

Yang Y.,Hohai University | Yang L.,Zhejiang Institute of Hydrogeology and Engineering Geology | Cai D.,Jiangsu Police Institute
Proceedings - International Conference on Natural Computation

The optimal design of groundwater remediation systems are often subject to uncertain hydrogeological parameters and multiple uncertain objectives, involving minimization of remediation cost, and minimization of contaminant mass remaining in the aquifer. To design a robust and reliable groundwater remediation system, the stochastic simulations (Monte Carlo simulation) with multiple realizations of uncertain parameters, which are generated by Sequential Gaussian Simulation (SGSIM), are applied to tackle the uncertainty analysis of an synthetic remediation site. In the present study, we propose a probabilistic multi-objective evolutionary algorithm, named probabilistic improved niched Pareto genetic algorithm (PINPGA). PINPGA was improved by using stochastic simulation for objection function evaluations and incorporating probabilistic Pareto ranking and niche technique into INPGA for multi-objective selection operator. The proposed algorithm is then applied to the synthetic groundwater remediation test case. The performances of the methodology generating the reliability of the Pareto-optimal solution are assessed and compared using Monte Carlo analysis. The optimization results indicate that using such an uncertainty-based multi-objective optimization scheme can give reliable solution to groundwater remediation design, giving decision makers a practical and robust optimization tool. © 2015 IEEE. Source

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