On the analysis of the high-resolution sequence stratigraphy and coal accumulating law of jurassic in Ordos Basin

The strata of Jurassic was divided into three tectonic sequences and eight se- quences of third rank,according to the developing feature of the tectonic inconformity and the transforming feature of the depositional system tracts.Also the identification and the division of the base-level cycle of different period were carried through.Therefore three cycles of super period,eight cycles of long period,twenty-four cycles of middle period and some cycles of short period were identified.From the overall character of the coal-accu- mulation in the Mesozoic,we can see that the Yan'an formation is of the best nature of coal bearing.When the coal bearing systems of Jurassic were depositing,the Ordos area is the coal accumulating basin of terrene of large scale and located in the same tectonic unit.But the local structure of different part and the paleolandform are different in the basin which resulted in the difference of the depositional environment.So the layer number and the distribution of the thickness of the coal beds are different in the different part of the ba- sin.The coal-accumulating action migrated regularly along with the development,evolve- ment and migration of the depositional systems.The layer numbers of the coal beds, which can be mined,are more in the north and west fringe of the basin,whose distributing area is extensive,and they are more steady in the landscape orientation,also the total thickness is great.Therefore the nature of coal bearing and the coal-accumulating action of different part changed obviously in the space in Ordos area.

Accumulation Laws of Nitrogen and Phosphorus in Wetland Plants

To study the accumulation regularity of nitrogen and phosphorus in typical constructive plants in coastal wetland,samples of Suaeda glauca(Bunge) Bunge,Phragmites austrahs and Tamarix chinensis Lour,were taken from the Yellow River Delta National Coast Wetland Nature Reserve,nitrogen and phosphorus content in plants was measured and analyzed.The results showed that ① nitrogen and phosphorus content in different wetland plants is correlated;② different species in the same place and the same species in different spaces show different accumulation regularity of nitrogen and phosphorus;③ nitrogen and phosphorus content in plants is closely related to nitrogen and phosphorus content in the habitat;④ nitrogen content in T.chinensis Lour,is the highest,the mean is 11.63 g/kg,and phosphorus content in S glauca(Bunge) Bunge is the highest,the mean is 1.38 g/kg;⑤ nitrogen content in the 3 species:T.chinensis Lour.> S.glauca(Bunge) Bunge > P.australis;⑥ nitrogen content in aboveground parts of all plants is significantly higher than that in underground parts,and phosphorus content in aboveground parts of all plants except S.glauca(Bunge) Bunge is significantly higher than that in underground parts;⑦ nitrogen content in the 3 species in the study area is significantly higher than phosphorus content in these species.