programme tuesday, july, 31 - Université de Caen Basse Normandie

Tidalites 2012, 8th International Conference on tidal environments, Caen, France – Abstract book
RAPID INFILLING OF MACROTIDAL ESTUARY DURING EARLY HOLOCENE IN
YEOCHARI TIDAL FLAT, GYEONGGI BAY, WEST COAST OF KOREA
Kyungsik CHOI, Jae Hoon JUNG, Joo Hee JO
FACULTY OF EARTH SYSTEMS AND ENVIRONMENTAL SCIENCES, CHONNAM NATIONAL
UNIVERSITY, 300 Yongbong-Dong, Buk-Gu, 500-757, Gwangju, Korea, tidalchoi@hotmail.com
Recent drilling campaign unveiled up to 12 m thick tidal rhythmites (TR) in the lower part of
Holocene successions at Yeochari tidal flat, west coast of Korea (Figure top). Various tidal
rhythms are encoded in the TR, which include diurnal inequality, synodic neap-spring cycle,
fortnightly inequality, and semi-annual cycle (Figure down). Reduced number of laminae in a
neap-spring tidal cycle, accentuated anomalistic cycle, fine-grained nature and close association
with organic-rich muds are all suggestive of upper intertidal origin of the TR. Abnormally thick
neap-spring tidal cycles are interpreted to be associated with monsoon discharge period.
Recurrence of TR bounded by organic-rich muds indicates that base-level has been fluctuated
during the deposition of the TR. Sedimentation rate inferred from the TR ranges from 1.7
cm/month to 10 cm/month with the maximum annual rate reaching up to 0.3 m. Stratigraphic
analysis with AMS dating indicates that TR-deposition occurred in the topographic lows between
main channels during early Holocene (10~8 ka) when sea-level rose at the maximum rate of 2 cm
per year. Given the stable tectonic condition of study area, the generation of accommodation
space due to the rapid base-level rise combined with antecedent topography that effectively
facilitated protection from storms seems to have played a key role in the creation and
preservation of unusually thick and delicate tidal records during Holocene transgression.
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