Sedimentary Characteristic Of The Beach-bar In The Es4 Formation In Shubei Area,West Sag Of Liaohe Depression

By the study of the tectonic conditions and the depositional environment in the Es4 formation in west of Liaohe Depression and compared with the Dongying Depression.It was predicted that the beach-bar sands deposited in this area.Based on the theoretical knowledge of the sequence stratigraphy,sedimentology and logging geology,and the investigation of the modern beach-bar sands.The data of the well log,the cores and the seism were analyzed.And then the new awareness of the sequence stratigraphy and the sedimentary characteristic in this area were achieved as fllows.1.Based on the principles and methods of the sequence stratigraphy,the ?logR and the seismic data,the high precision sequence stratigraphic was established.The Es4 was divided into two third-order sequences,SQ1 and SQ2.The SQ1 consisting of three systems tracts,i.e.a LST,a TST and an HST.And a LST and a TST were included in the SQ2 in the Es4 formation.And then,the parasequence set and the subsequence were analyzed.2.By the analysis of the sedimentary structure and the well log data.Beach-bar sands were recognized for the first time in Shubei and surrounding areas during SQ2.The distribution and evolution characteristic of the beach-bar sands were studied in parasequence set.In the plane,the beach sands were widely distributed,the bar sands were arranged two columns and they distributed on both sides of the buried hill.In vertical,the forms of the sands were successive development,but the area was reduced with the depth of the water increased.3.By the investigation of the modern beach-bar sands,it could be determined that the control factors of the beach-bar include palaeogeomorphology,palaeowater depth,palaeowind and sediment source.These factors could be calculated by well log data,the seismic data,the cores and the slice analysis.And their influence to the distribution of the beach-bar sands was analyzed:the palaeogeomorphology determined the phylogenetic position of the beach-bar;the sediment source determined the degree of the beach-bar;the palaeowater depth not only reflected the change of the accommodation space,but also determined the type of the sediments;the palaeowind determined the hydrodynamic conditions and then determined the distribution characteristics of the beach-bar sands.