Mid-Miocene Unconformity

The Mid-Miocene Unconformity (MMU) is recognized throughout the South China Sea passive margin. It marks the end of rifting that created the marginal basin. It is understood to represent the break-up unconformity when active rifting gave way to sea-floor spreading in the contiguous southwest extension of the abyssal plain. Anomalies are not constrained in this part of the abyssal plain because the oceanic domain is very narrow and the magnetic anomalies not well expressed. However, magnetic anomaly 5c, whose age is estimated at 16.6 Ma, has been identified 300 km NE of the wedge-shaped SW extension of the oceanic area (Huchon et al., 2001). There is no direct drilling evidence of the age of the MMU.