| Based on the outcrop,logging,elements and Milancovitch cycles,the lower-order unconformities were conducted constrained by systemetic scale of unconformities in the Bamai area,Tarim Basin.On the basis of recognition of the lower-order unconformities,combined with characteristic and time of cycle,we could set up the sequence stratigraphy of high frequency,within which the nature of the unconformity surfaces and their sedimentary and diagenetic environment could be analysed.And the cores,thin slices,isotopes and inclusions could help us set up the diagenetic evolution sequence.And fanally,the law of development of the carbonate karst reservoir could be studied through the comprehensice analysis of“sequence-sediment-diagenesis" in order to set the model.The lower unconformities,such as T76?T7~8could be recognized.And both of them have the characters of peak of NGR caused by high value of U,and however,there were distinctions of them in the aspects of outcrop occurrence,resistivity,and depositional environment.From the bottom of the Lower-Middle Ordovician to the top,SQ1-SQ4 could be divided and for the lasting time of the fourth-order cycle was about 0.4-1.5Ma controlled by long eccentricity,and there were eleven fourth-order sequences.T7~8 was the typical sedimentary-diagenetic surface and T76 was the sedimentary one.Diagenesis in the sequence stratigraphy framework suggested that meteoric vadose or phreatic environment was always existing in the late stage of HST and early stage of TST,with which the condition was the same in the fourth-order sequence.Compared with that of surface of T7~8,the extent of exposure and leaching of T76 was weak and solution pores were few.The microfacies of dolomitic limestone and calcareous dolomite and sandy beach exsiting in the late stage of HST could be characterized by leaching of meteoric vadose or phreatic environment.The soloution pores of meteoric environment controlled by the surfaces of T7~8 and T76developed in the syndiagenesis. |
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