Organic matter enrichment in the first member of the Xiagou formation of the lower Cretaceous in the Jiuquan Basin, China

The sources and enrichment of organic matter in a sediment core in the first member of the Xiagou Formation(K_1g^1) from the Chang 2-2 borehole of the Jiuquan Basin,NW China,have been examined using Rock-Eval,maceral,carbon isotopes and biomarker data.This data indicates that highly variable organic matter sources and preservation conditions in response to climate change.TOC content,HI,and δ^(13)C value were strongly correlated with the abundance of gammacerane,woody organic matter content,steranes/hopanes ratio,and C_(29) sterane content.This correlation demonstrates the importance that the control of the salinity of the depositional environment and organic matter sources can have upon the enrichment,type,and carbon isotopic composition of organic matter.In the Jiuquan Basin's relatively high temperature and arid climate,high salinity lakes with high primary productivity of algae,planktons,and bacteria,and good organic matter preservation conditions(anoxic bottom water) resulted in the enrichment of isotopically-light algae-bacterial organic matter.In the Jiuquan Basin's regions with a relatively low temperature and wet climate,fresh lakes with low primary productivity of algae,planktons,and bacteria received significant terrigenous high plants input,resulting in the deposition of a low abundance of isotopically heavier terrestrial organic matter.

Landslide and Basin Self-organized Criticality in the Lushan Hot Spring Area

Defining a basin under a critical state （or a self-organized criticality） that has the potential to initiate landslides, debris flows, and subsequent sediment disasters, is a key issue for disaster prevention. The Lushan Hot Spring area in Nantou County, Taiwan, suffered serious sediment disasters after typhoons Sinlaku and Jangmi in aoo8, and following Typhoon Morakot in 2009. The basin＇s internal slope instability after the typhoons brought rain was examined using the landslide frequency-area distribution. The critical state indices attributed to landslide frequency-area distribution are discussed and the marginally unstable characteristics of the study area indicated. The landslides were interpreted from Spot 5 images before and after disastrous events. The results of the analysis show that the power-law landslide frequency-area curves in the basin for different rainfall-induced events tend to coincide with a single line. The temporal trend of the rainfall- induced landslide frequency-area distribution shows 1If noise and scale invariance. A trend exists for landslide frequency-area distribution in log-log space for larger landslides controlled by the historical maximum accumulated rainfall brought by typhoons. The unstable state of the basin, including landslides, breached dams, and debris flows, are parts of the basin＇s self-organizing processes. The critical state of landslide frequency-area distribution could be estimated by a critical exponent of 1.0. The distribution could be used for future estimation of the potential landslide magnitude for disaster mitigation and to identify the current state of a basin for management.

香草美食

可以吃进肚子的植物,其实不单只有常吃的蔬菜如大白菜、莴苣等等那么简单,其实还有不少香草、鲜花,都是国际厨师们爱用的煮食素材。这些植物通常都带有特别的草香,食物加上以它们来做香料或调味料,都变得充满自然风味,令人仿如置身春日的原野！

Primary dolostone related to the Cretaceous lacustrine hydrothermal sedimentation in Qingxi sag, Jiuquan Basin on the northern Tibetan Plateau

Based on comprehensive studies in petrography, petrofabric analysis and geochemistry, this paper describes a unique and rare laminated micritic ferruginous primary dolostone crystallized and precipitated from the alkaline hot brine under the conditions of the Mesozoic faulted lake basin. The main rock-forming mineral of this dolostone is ferruginous dolomite with a micritic structure. This dolomite mostly exhibits laminae of 0.1-1 mm thick and is often discovered with other minerals, such as albite, analcite, barite and dickite, which have at least two types of interbedded laminae. Petrogeochemistry reveals that this dolostone contains a large number of typomorphic elements of hydrothermal sedimentation, including Sb, Ba, Sr, Mn, and V. In addition, the LREE is in relatively high concentrations and possesses the typical REE distribution pattern with negative Eu anomaly. Oxygen isotope values （C^ISOpDB） range from 5.89%~ to 14.15%o with an average of 9.69%0. The ratio of 87Sr/86Sr is between 0.711648 and 0.719546, with an average of 0.714718. These data indicate that the depositional environment is a stable, blocked, anoxic low-lying hot brine pool in the bottom of deep lake controlled by basement faults. The hydrothermal fluid is the alkaline hot brine formed by the combination of the infiltration lake water and mantle-derived magmatic water, consisting of many ions, including Ca2＋, Mg2＋ and Fe2＋. Under the driving flow power of magmatic heat, gravity and compaction, the hy- drothermal fluid overcame the overburden pressure and hydrostatic pressure of the lake water body, and boiled to explosion, and then the explosion shattered the original laminated micritic ferruginous primary dolostone near the vent and then formed a new type of dolostone called shattered ＂hydroexplosion breccias＂. In the low-lying, unperturbed hot brine pool, far from the vent, the laminated micritic ferruginous primary dolostone was quickly crystallized and chemicals precipitated from the hy- drotherm. This study of special rocks contributes to research into the causes of the formation of lacustrine carbonate rocks and dolostone. In particular, it provides new examples and research insights for future studies of the lacustrine dolomite from the similar Mesozoic and Cenozoic basins in China.