Although the mouth of the Yellow River has fluctuated widely north and south of the Shandong peninsula within the historical record, the Yangtze has remained largely static. Based on studies of sedimentation rates, however, it is unlikely that the present discharge site predates the late Miocene (c. 11 Ma).[53] Prior to this, its headwaters drained south into the Gulf of Tonkin along or near the course of the present Red River.