Geochemical evidence for initiation of the modern Mekong Delta in the southwestern South China Sea after 8 Ma

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doi: 10.1016/j.chemgeo.2017.01.008
Author(s): Liu, Chang; Clift, Peter D.; Murray, Richard W.; Blusztajn, Jerzy; Ireland, Thomas; Wan Shiming; Ding Weiwei
Author Affiliation(s): Primary:
Louisiana State University, Department of Geology and Geophysics, Baton Rouge, LA, United States
Other:
Boston University, United States
Woods Hole Oceanographic Institution, United States
Chinese Academy of Sciences, Institute of Oceanology, China
State Oceanic Administration, China
Volume Title: Chemical Geology
Source: Chemical Geology, Vol.451, p.38-54. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541 CODEN: CHGEAD
Note: In English. Includes appendices. 107 refs.; illus., incl. 3 tables, sketch map
Summary: Sedimentary records in the southwestern South China Sea reflect the evolving erosion and drainage systems that have operated in Southeast Asia during the Neogene. Analyses of the chemistry and clay mineral composition of sediments from International Ocean Discovery Program (IODP) Site U1433 allow us to examine these processes over the last 17 Ma. Sediment older than 8 Ma was deposited relatively slowly. Sr and Nd isotopes indicate a variable provenance with sequences of less and more altered material accompanied by strong changes in the proportion of smectite. Sediment flux was probably from Indochina, as well as from a more primitive volcanic source, most likely the Palawan ophiolite and/or Luzon. Sediments younger than 8 Ma show a more stable Sr and Nd isotope character, indicating sources close to those seen in the modern Mekong River, although with some influx from smaller rivers draining the Indochina margin especially from 4 to 8 Ma. Our data are consistent with seismic estimates for an onset to the Mekong in its present location after 8 Ma, following an avulsion from the Gulf of Thailand.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 02 Geochemistry; 23 Surficial Geology, Geomorphology; Alkaline earth metals; Asia; Avulsion; Cenozoic; Chemical composition; Clay minerals; Deltas; Expedition 349; Far East; Fluvial features; Fluvial sedimentation; Gulf of Thailand; IODP Site U1433; International Ocean Discovery Program; Isotope ratios; Isotopes; Landform evolution; Major elements; Mekong Delta; Metals; Mineral composition; Miocene; Neodymium; Neogene; North Pacific; Northwest Pacific; Pacific Ocean; Provenance; Rare earths; Sedimentation; Sediments; Sheet silicates; Silicates; Smectite; South China Sea; Southwestern South China Sea; Sr-87/Sr-86; Stable isotopes; Strontium; Tertiary; Trace elements; Upper Miocene; Vietnam; West Pacific
Coordinates: N125508 N125508 E1150251 E1150250
N083000 N102000 E1065500 E1044000
Record ID: 2017041337
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands