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This paper reports the analysis on cores and rock slices, data on seismic and logging activities, characteristics of core samples, and the paleogeographic background of the Yingcheng Formation of the Xujiaweizi faulted depression in the Songliao Basin. The results show that some of the volcanic rocks were formed during subaquatic eruptions. These subaqueous volcanic rocks are further characterized by the interbedded black mudstone and tuffite, the presence of double-layer perlite enclosing aphyric or sparsely phyric rhyolite, the presence of a bentonite layer, and the coefficient of oxidation (FeO/FeO). The types of rocks are volcanic breccia, lava breccias, perlite, rhyolite, tuff and sedimentary tuff. The subaquatic eruptions are distributed mainly in Wangjiatun, Shengping, Xuxi, Xuzhong, and Xudong. The XS-1 area is the most typical. The organic abundance of overburden mud rocks within the volcanic rocks of the Yingcheng Formation indicates that these rocks represent high-quality source rocks. The analysis also shows that continental subaquatic volcanic eruptions provide a rich supply of minerals and energies for the lake basin and increase the organic matter content in the water. Moreover, the water differentiation provides a good reducing environment for the conservation of organic matter, and is beneficial for the formation of high-quality source rocks. Finally, we propose a hypothesis to describe the mode of subaquatic eruptions and the formation of high-quality source rocks. [ABSTRACT FROM AUTHOR]

By using crater impact morphological theory and mathematics modeling, the paper studies the cratering process and morphological features of the Xiuyan Crater in Northeast China based on remote sensing imagery, digital elevation model (DEM) and drilling and measuring data. The results show that: 1) Simulated calculation indicates the diameter of the transient crater was 1406±12 m and the depth was 497±4 m. The diameter of the final crater was 1758±15 m and the depth was 374.5±3.5 m; the thickness of the breccia lens was 188.5±0.5 m. The data is basically the same as previous drilling data. 2) Preliminary determination of the size of Xiuyan impactor: The diameter at about 55 m for an iron meteorite, and about 115 m for a stony meteorite. 3) The depth-to-diameter ratio is 0.143, similar to the typical simple crater. The circularity index of the Xiuyan Crater is 0.884, indicating erosion and degradation. 4) The distribution pattern of radial fractures has priority in NW-SE and WNW-ESE and these fractures control the development and evolution of drainage inside the crater. [ABSTRACT FROM AUTHOR]

Assessments of the impacts of land use and land cover changes (LUCC) on the terrestrial carbon budget, atmospheric CO concentration, and CO-related climatic change are important to understand the environmental effects of LUCC and provide information about the effects of historical carbon emissions. Using regional land cover reconstructions from historical records, with a bookkeeping model, we estimated the carbon sink changes caused by historical cropland expansion in Northeast China during the past 300 years. The conclusions are as follows: (1) There was a dramatic land reclamation of cropland during the past 300 years in Northeast China. Approximately 26% of the natural land was cultivated, and 38% of the grassland and 20% of the forest and shrubland were converted to cropland. (2) The carbon emission induced by cropland expansion between 1683 and 1980 was 1.06-2.55 Pg C, and the estimation from the moderate scenario was 1.45 Pg C. The carbon emissions of the soil carbon pool was larger than that from the vegetation carbon pool and comprised more than 2/3 of the total carbon emissions. (3) The carbon emissions of the three provinces in Northeast China were different. Heilongjiang Province had the largest carbon emissions, and Jilin Province had the second largest emissions. (4) The primary source of carbon emissions was forest reclamation (taking 60% of the total emissions in the moderate scenario), the secondary source was grassland cultivation (taking 27%), and the tertiary sources were shrubland and wetland reclamation (taking 13%). Examination on the data accuracy revealed that the high-resolution regional land cover data allowed the carbon budget to be evaluated at the county level and improved the precision of the results. The carbon emission estimation in this study was lower than those in previous studies because of the improved land use data quality and various types of land use change considered. [ABSTRACT FROM AUTHOR]

Trends of the tropical cyclones (TCs) influence on China and its four subregions, namely the South China (SC), East China (EC), Northeast China (NEC), and China's inland area (CI), are detected by applying quantile regression to the CMA-STI tropical cyclone best track and related severe wind and precipitation observation datasets. The results indicate that in the past 50 years, the number of TCs affecting China and its four subregions has remained steady, except that the frequency in extremely active years has decreased not only in China as a whole, but also in NEC. In addition, TC activity is found to have weakened over the northwest South China Sea, Guangdong, and Shandong Peninsula. However, the most important changes in seasonality are found in the first quartiles of the number of days of TCs affecting CI. While the extreme values of sustained winds all have decreasing trends, the extreme values of wind gusts are completely different not only among different orders of extreme values, but also among different subregions. However, the trends of extreme TC rainfall, namely the maximum storm precipitation and the maximum 1-h precipitation, are not significant. [ABSTRACT FROM AUTHOR]