| The atmospheric flow field is an important component of climate. It could not only provide information for global circulation models, but also act as an important controller for depositional processes as a geologic agent. However, paleowind fields are less well studied because ancient winds were ephemeral and often left little trace of their passing. A large amounts of beach-bar complexes, which are closely associated with paleowind field during their formation and became petroleum exploration targets these years, were preversed in Paleogene shore-shallow lake environments in east China. By investigating how wind-waves control the formation of beach-bar complexes, the study of paleowind field is introduced in this dissertation, by using core data, well-log data and seismic data and taking the upper 4th member of Shahejie Formation in Eocene Dongying Depression as an example. It is proposed that the formation of beach-bar complexes is controlled by the wind-source-basin system. The main achievements are as follows:(1) A “wind-sources-basin” geological model was proposed. In the “wind-source-basin” system, the wind field, including the consequent climate condition, is the primary control of structure and texture of depositional bodies, while the provenance provides the basic constraints in material to be supplied, and the tectonic setting/evolution of the basin determines the position, extent and scale of depositional bodies. These controlling factors, which are mutually interacting, form a unified system, and determine the spatial and temporal extent of sedimentary systems. The model proposed here can serve as a novel tool for hydrocarbon reservoir prediction.(2) Sequence stratigraphy and depositional systems of the upper forth member of Shahejie Formation(Es41) in Dongying Depression were summarized and studied. The Es41 Formation was classified as a classic third-order sequence, i.e., a lowstand systems tract(LST), a transgressive systems tract(TST) and a highstand systems tract(HST). The precision of the stratigraphy was as high as parasequence in certain areas. Therefore, an isochronal stratigraphic frame was established for further studying the “wind(climate)-source-basin” system. A total of 7 depositional systems, namely fan-deltas, subaqueous gravity flow deposits, deltas, clastic beach-bar complexes, storm deposits, carbonate beach-bar complexes and fine-grained deposits, were identified based on previous research results as well as available subsurface data obtained by core drilling and borehole logging in this ancient basin.(3) The genetic model of beach-bar complexes was proposed. Based on the relationships between wave shoaling processes and sediment transportation, several terms distinguish different beach and bar deposits were given. Bars formed at the breaker zone, surf zone and swash zone are called outer bar(or breaking bar), inner bar and coastal bar, respectively, while beaches formed at the shoaling zone, reformed wave zone and swash zone are called outer beach, inter-bar beach and coastal beach, respectively. Overall, bar deposits are surrounded by beach deposits in a plane view. The beach-bar complex acts as a full response of the total “wind-sources-basin” system.(4) Quantitative reconstruction of paleowind field by innovative using beach-bar complexes was proposed. ①The strike and asymmetry in transverse section of a breaking bar can be used to determine ancient wind direction based on the self-organizational model. ② The thicknesses of lacustrine breaking bars and/or gravelly coastal bars can be used to accurately determine ancient wind strength. In addition to acting as a direct controlling factor to depositional processes, paleowind field may control paleoclimate conditions such as temperature and humidity. These methods could not only provide new perspectives on delineating paleowind as well as paleoclimate conditions, but also serve as a tool for beach-bar complexes studies about their formation and prediction. |
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