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Description:
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The South China Sea is a region of significant importance in terms of the records
of SE Asian tectonics , including Tibetan Plateau uplift , and the onset and evolution of
the East Asian monsoon . The Mekong River has been a dominant sediment source since
at least late Miocene time and has headwaters on the eastern Tibetan Plateau .
Understanding the Pliocene to Recent stratigraphy of the paleo -Mekong Delta and
associated shelf -edge deposits aids in understanding changes in accommodation , sea
level , and sediment supply . This record might then be useful in interpreting the longterm
history of basin evolution in the Nam Con Son Basin .
Nine sequence boundaries and associated sequences are recognized along the late
Miocene to latest Pleistocene shelf in the East Nam Con Son Basin . Age constraints
were assigned to key stratigraphic horizons by correlating sequence boundaries with
published sea level curves . Accommodation in the study area is controlled by shelf -edge
compaction , rift -related thermal subsidence , non -rift -related anomalous subsidence ,Two primary sources supplied sediment to the southwestern South China Sea
during Pliocene to Recent time and likely include the paleo -Mekong Delta and a fluviodeltaic
system originating from the Sunda Shelf , such as the Molengraaff River . Changes
in thickness , area , and location of Pliocene to Recent shelf -edge delta deposits reflect
changes in accommodation and sediment supply over time , as well as progradation of
the shelf edge during Pliocene to Recent time and avulsion of the shelf edge delta .
Anomalous subsidence of LGM shelf edge deposits is estimated at approximately
40 -50 m deeper than expected . The current depth of the LGM deltaic wedge may
indicate renewed rapid tectonic subsidence during the last 18 ,000 yrs , possible
compaction effects or a combination of these .
eustatic change , and shelf edge faulting . |