Effects of Intracratonic Strike-slip Fault on the Differentiation of Carbonate Microfacies: A Case Study of a Permian Platform Margin in the Sichuan Basin(SW China)

In intracratnoic basins, the effect of strike-slip faults on sedimentary microfacies is generally underestimated due to their small scale. Based on the integration of core, well logs, and three-dimensional seismic data, this study presents a comprehensive analysis of the Permian carbonate platform and strike-slip faults in the southwestern Kaijiang-Liangping trough of the Sichuan Basin. The relationship between strike-slip faults and Permian carbonate microfacies is investigated. The results reveals the existence of a NW-trending strike-slip fault zone along the platform margin, exhibiting clear segmentation. The western side of the study area exhibits a rimmed platform margin characterized by type I reefs, which corresponds to the presence of a large-scale strike-slip fault zone. In contrast, the eastern side is characterized by a norimmed and weak rimmed platform margin, accompanied by type II reefs, which align with smaller strike-slip fault zones. It was found that the strike-slip fault had some effects on the platform and reef-shoal complex of the Permain Changxing Formation. First, the platform was divided by strike-slip fault into three segments to show rimmed, week rimmed and norimmed platform. Second, reef-shoal complex devolped along the faulted high position in the strike-slip fault zone, and separated by faulted depression. Third, strike-slip faults can offset or migrated the reef-shoal complex and platform margin. Additionally, the thickness of the platform margin varies across strike-slip fault zone, which is related to the activity of strike-slip faults. The strike-slip faults affect the microfacies by controlling the pre-depositional paleotopography. This case suggests that the strike-slip faults play a crucial role in the diversity and distribution of carbonate microfacies in the intracratonic basin.

Sediment pattern&rate of bathymetric changes due to construction of breakwater extension at Nowshahr port

Erosion,scour and sedimentation are the most common phenomena which should be considered in the design of marine structures.Seas and oceans are dynamic environments,hence studying them in more details,gathering more information about their bathymetric changes and pursuing their historical evolution could be beneficial in the efficient design of marine structures such as:jetties,groins and breakwaters.To achieve this goal one desperately needs to know about currents and waves and the effects of their interactions as well as the rate of sedimentation(Net Gain),and erosion(Net Loss)in the field.On the other hand,to obtain a sufficient depth to facilitate marine traffics in the harbors the rate of sediment deposition must be calculated,offering effective annual dredging programs.In this research the pool of Nowshahr port and some parts to the east and west were modeled.Sediment transport direction was compatible with the counter-clock-wise circulation of the Sothern part of Caspian Sea.Wind data,water surface elevation,and hydrographic points from the bathymetric surveys applied in the hydrodynamic module of Mike 21 and the output of the hydrodynamic module(HD)were used as inputs for sediment transport module(ST).The result of the ST module shows that the main direction considering dominant waves is from northwest of the Caspian Sea to the southeast.Also,net rate of sediment transfer is from west to east.By approaching to the main breakwater arms from the west side sediment transport rate decreases which means deposition occurs behind the western arm.