Origin of multiple flat tables on Caiwei Guyots in West Pacific

Multi-beam bathymetric data suggests a special topographic feature on the Caiwei Guyots in the West Pacific. The sub-bottom profile data obtained in 2015 by R/V "HAI YANG LIU HAO" suggests that there are several flat tables developed on the top of guyots at the water depths ranging 1350-1735m. The difference in water depth between the flat tables is around 300-450m. Sub-bottom profile suggests that the sediment on the top of guyots is 35-100m thick. Taking the sediment thickness out of consideration, the water depth difference between flat table basements still exceeds 200m, which means that the difference of sediment thickness is not the main reason causing the multi-tables. Through comparison of topographic features among the Caiwei Guyots, Ganquan terrace and Yongshu Reef in the South China Sea, it is discovered that the relative sea-level change is not the main reason to cause the multi-tables either. Carbonate deposits are found in the fringes of the tables, which indicates that the guyots were close to the sea level when the flat top was formed. It is then deduced that the multi-tables are probably generated by vertical tectonic movement within the region of Caiwei Guyots. According to topographic features and local geological background, there are probably two northwest normal faults in the Caiwei Guyots, which caused vertical tectonic movement and the formation of multi-tables. One of the faults dips to northeast and the other to southwest.