The Characters And Control Of Tectonics On Sequence Stratigraphy Of The Lower Tertiary In Jiyang Basin

This paper studies the characters and control of tectonics on sequence stratigraphy of the Lower Tertiary in Jiyang basin. Jiyang basin experienced several tectonic activities from the Archaen to now. The Lower Tertiary of the basin is a composite half-graben basin which is faulted in the north and onlapped in the south. It is controlled by three groups of extensional and extension-twisted faults. Under the control of these faults, the Lower Tertiary in Jiyang basin is characterized by 1. an intense segmentation of the structural framework; 2. multiple types of tectonics; 3. successively of structures; 4. stratification and zonation of tectonics.In this paper we used tectonic simulation method to simulate the tectonic evolvement of the Zhanhua depression. Its results reveal that the structure in which the sags and uplifts are arranged alternately was caused by intense expanding activity. Its extensional rate reached 30% to 100%. According to the development of sequence stratigraphy and the result of the extensional rate in Zhanhua depression, Jiyang basin experienced 4 times of intense extensional activities and 11 times of weak extensional activities in the early Tertiary, which controlled the development of 2nd-order and 3rd-order sequence respectively. We used the sound radiation method to study the compressing tectonics of Dongying depression in the Cenozoic. Its results display that the Dongying depression experienced 4 times of intense compressing tectonic activities and 4 powerless compressing tectonic activities after the Age of Es3, which represent the compressing tectonic activities in the end of the development of 2nd-order and 3rd-order sequence respectively. In the initial stage of each sequence the tectonic activities were extending and in the final stage the tectonic activities were compressing.By the research on the extending and compressing tectonic activities in Jiyang basin we can divide the lower Tertiary into one lst-order tectonic sequence, four 2nd-order tectonic sequences and six 3rd-order tectonic sequences, which are consistent with the sequence stratigraphy.Tectonic activities are the main factors in control of the sequences below the 3rd-order sequence of the Lower Tertiary in Jiyang basin. The activity of faults is the leading form of tectonic activity. So the activity of faults is the primary factor incontrol of the development of 1st-order, 2nd-order, and 3rd-order sequence. Thecontrolling effect of fault activity are as below: the activity of faults could create theaccumulation for the sequence development; the intensity of fault activity varied ineach stage, so it could control the thickness, shape and the superposition ofpara-sequences in each stage.