The last glacial period came to an abrupt end about 19,000 years ago (19 ka) when sea levels rose rapidly, reaching a maximum of about 4.5 m above present levels in the early Holocene about 8 ka. At this time the shoreline of the South China Sea almost reached Phnom Penh and cores recovered from near Angkor Borei contained sediments deposited under the influence of tides, and salt marsh and mangrove swamp deposits. Sediments deposited in the Tonle Sap Great Lake about this time (7.9–7.3 ka) also show indications of marine influence, suggesting a connection to the South China Sea. Although the hydraulic relationships between the Mekong and the Tonle Sap Great Lake systems during the Holocene are not well understood, it is clear that between 9,000 and 7,500 years ago the confluence of the Tonle Sap and the Mekong was in proximity to the South China Sea.