Relative sea-level changes during the holocene in Bangladesh

Towhida Rashid, Shigeyuki Suzuki, Hiroshi Sato, M. H. Monsur, S. K. Saha

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

This paper presents a reconstruction of the Holocene paleo-environment in the central part of Bangladesh in relation to relative sea-level changes 200 km north of the present coastline. Lithofacies characteristics, mangal peat, diatoms and paleophysiographical evidence were considered to reconstruct the past position and C-14 ages were used to determine the time of formation of the relative sea level during the Holocene. With standard reference datum, the required m.s.l. at the surface of five sections was calculated. The relative sea-level (RSL) curve suggests that Bangladesh experienced two mid-Holocene RSL transgressions punctuated by regressions. The curve shows an RSL highstand at approximately 7500 cal BP, although the height of this highstand could not be determined because the transgressive phase was observed in a bioturbated sand flat facies. The curve shows a regression of approximately 6500 cal BP, and the RSL was considerably lower, perhaps 1-2 m, than the present m.s.l. The abundant marine diatoms and mangrove pollens indicate the highest RSL transgression in Bangladesh at approximately 6000 cal BP, being at least 4.5 to 5 m higher than the modern m.s.l. After this phase, the relative sea level started to fall, and consequently, a freshwater peat developed at approximately 5980-5700 cal BP. The abundant mangrove pollens in the salt-marsh succession shows the regression at approximately 5500 cal BP, when it was 1-2 m higher than the modern sea level. The curve indicates that at approximately 5000 cal BP and onwards, the RSL started to fall towards its present position, and the present shoreline of Bangladesh was established at approximately 1500 cal BP and has not noticeably migrated inland since.

Original languageEnglish
Pages (from-to)136-150
Number of pages15
JournalJournal of Asian Earth Sciences
Volume64
DOIs
Publication statusPublished - 2013

Fingerprint

sea level change
Holocene
sea level
highstand
transgression
mangrove
peat
diatom
pollen
lithofacies
saltmarsh
shoreline
coast

Keywords

  • Bangladesh
  • Diatom
  • Facies
  • Highstand
  • Holocene
  • Pollen
  • Relative sea-level

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Geology

Cite this

Relative sea-level changes during the holocene in Bangladesh. / Rashid, Towhida; Suzuki, Shigeyuki; Sato, Hiroshi; Monsur, M. H.; Saha, S. K.

In: Journal of Asian Earth Sciences, Vol. 64, 2013, p. 136-150.

Research output: Contribution to journalArticle

Rashid, Towhida ; Suzuki, Shigeyuki ; Sato, Hiroshi ; Monsur, M. H. ; Saha, S. K. / Relative sea-level changes during the holocene in Bangladesh. In: Journal of Asian Earth Sciences. 2013 ; Vol. 64. pp. 136-150.
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AB - This paper presents a reconstruction of the Holocene paleo-environment in the central part of Bangladesh in relation to relative sea-level changes 200 km north of the present coastline. Lithofacies characteristics, mangal peat, diatoms and paleophysiographical evidence were considered to reconstruct the past position and C-14 ages were used to determine the time of formation of the relative sea level during the Holocene. With standard reference datum, the required m.s.l. at the surface of five sections was calculated. The relative sea-level (RSL) curve suggests that Bangladesh experienced two mid-Holocene RSL transgressions punctuated by regressions. The curve shows an RSL highstand at approximately 7500 cal BP, although the height of this highstand could not be determined because the transgressive phase was observed in a bioturbated sand flat facies. The curve shows a regression of approximately 6500 cal BP, and the RSL was considerably lower, perhaps 1-2 m, than the present m.s.l. The abundant marine diatoms and mangrove pollens indicate the highest RSL transgression in Bangladesh at approximately 6000 cal BP, being at least 4.5 to 5 m higher than the modern m.s.l. After this phase, the relative sea level started to fall, and consequently, a freshwater peat developed at approximately 5980-5700 cal BP. The abundant mangrove pollens in the salt-marsh succession shows the regression at approximately 5500 cal BP, when it was 1-2 m higher than the modern sea level. The curve indicates that at approximately 5000 cal BP and onwards, the RSL started to fall towards its present position, and the present shoreline of Bangladesh was established at approximately 1500 cal BP and has not noticeably migrated inland since.

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