Diatom Responses to Holocene Environmental Changes in the Tiền Delta - Mekong River System
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Abstract
Abstract: The environmental changes in the Tiền delta during the Holocene were revealed by diatom investigation of 3 deep boreholes along the coastal zone of the Mekong delta, Vietnam. The data shows that the studied area was transformed from a terrestrial condition to coastal area at about 8000 years BP. The dominance of marine diatoms species from 40m to 15m in the borehole LKBT2, from 36.5m to 18m in the borehole LKTB3 and from 20m to 14 m in the borehole LKTB1 indicates that studied area at about 5000-7000 years BP was dominated by marine environment such as lagoon or estuary. This change is a result of the Flandrian transgression. The sandy bar or supratidal flat characterized by the strong decrease of diatoms in number of species and individuals shows a regression time at about 4000 years BP. The dominance of diatoms in the uppermost part in the 3 boreholes shows a coastal environment in the late Holocene.
Keywords:Diatoms, environmental changes, Holocene, Tiền delta, coastal environment.References
[2] Van Lap Nguyen, Thi Kim Oanh Ta., Masaaki Tateishi, ,2000. Late Holocene depositional environments and coastal evolution of the Mekong delta, Southern Vietnam. J. Asian Earth Sci. 18, 427-439.
[3] Van Lap Nguyen, Thi Kim Oanh Ta., Masaaki Tateishi,, Iwao Kobayashi, Masatomo Umitsu, Yoshiki Saito, 2005. Late Quaternary depositional sequences in the Mekong delta, Vietnam. In: Chen, Z.Y.,Saito,Y.,Goodbred Jr,S.L.(Eds.), Mega- deltas of Asia Geological Evolution.
[4] Van Lap Nguyen., Thi Kim Oanh Ta, Yoshiki Saito, 2010. Early Holocene initiation of the Mekong delta, Vietnam, and the response to Holocene sea-level changes detected from DT1 borehole analyses. Sedimentary Geology, 230 (2010) 146-155.
[5] Thi Kim Oanh Ta, Van Lap Nguyen, Masaaki Tateishi, Iwao Kobayashi, Yoshiki Saito, 2001. Sedimentary facies, diatom and foraminifer assemblages in a late Pleistocene–Holocene incised-valley sequence from the Mekong delta, Bentre Province, Southern Vietnam: the BT2 core. J. Asian Earth Sci. 20, 83-94.
[6] Thi Kim Oanh Ta., Van Lap Nguyen., Masaaki Tateishi, Iwao Kobayashi, Yoshiki Saito, Toshio Nakamura 2002a. Sediment facies and Late Holocene progradation of the Mekong delta in Bentre province, southern Vietnam: an example of evolution from a tide-dominated to a tide- and wave-dominated delta. Sed. Geol. 152, 313-325.
[7] Susumu Tanabe, Yoshiki Saito, Yoshio Sato, Yuichiro Suzuki, Sin Sinsakul, Suwat Tiyapairach, Niran Chaimanee, 2003. Stratigraphy and Holocene evolution of the mud-dominated Chao Phraya delta, Thailand. Quaternary Science Reviews 22 (2003) 789-807.
[8] Ulrike Proske, Till J.J. Hanebuth, Hermann Behling, Van Lap Nguyen, Thi Kim Oanh Ta and Bui Phat Diem, 2010. The palaeoenvironmental development of the northeastern Vietnamese Mekong River Delta since the mid Holocene. The Holocene published online 27 July 2010.
[9] Hustedt, F., 1959. Die Kieselalgen Deutschlands, O ¨ sterreichs undder Schweiz, 2 Teil. Koeltz Scientific Books, Koenigstein. English translation, 1985, 918 pp.
[10] Jouse, 1977. Atlas of microorganisms in bottom sediments of the oceans. Diatoms, radiolarian, silicoflagellates and coccoliths. Publishing house “Nauka”. Moscow. (In Russia).
[11] F. E. Round, R. M. Crawford, D. G. Mann, 1990. The Diatoms: biology and morphology of genera. Cambridge University press. 747p.
[12] Trương Ngọc An, 1993. Planktonic diatom in the Bien Dong, Vietnam. Publishing House of Science and Technology(in Vietnamese).
[13] McQuoid M.R., Nordberg K., 2003. The diatom Paralia sulcata as an environmental indicator species in coastal sediments. Estuarine, Coastal and Shelf Science, 56 (2003) p.339-354.
[14] Hasle, G. R., & Syvertsen, E. E. (1996). Marine diatoms. In C. R. Lakes. Encyclopedia of Quaternary Science. Editor-in- chief Scott A. Elias. Vol. 1, p. 514-523, Elsevier