SUMMARY

Some preliminary results about paleo-tsunami study in the coastal area of
Nghệ An Province

Cao Đình Triều, Ngô Gia Thắng, Bùi Anh Nam

In the coastal area of Nghệ An Province there exist "geological anomalies", especially the appearance of grounds of the Arca granosa with the Placura placenta and knolls of the Placura placenta with the Arca granosa shells. On the basis of our investigation, the new results can be made as follows:

- Knolls of the Placura placenta with the Arca granosa shells in the Quỳnh Văn and Nghi Tiến areas and grounds of the Arca granosa with the Placura placenta situated below in the Quỳnh Nghĩa and Diễn Châu plains and along the Nghi Yên coast have the age of 4,500-4,300 years.

- The appearance of the Placura placenta - Arca granosa shell grounds and knolls have not the sources from marine transgression in Holocene, tectonic movements or artificial activities.

- In the Nghệ An coastal areas occured strong paleo-earthquakes having the C¹⁴ ages of 4,500-4,300, 900-600 years (with some historic records) which are manifested by great regional slope collapse, some of which might be caused by tsunami.

- Such "geological anomalies" are: knolls of the Placura placenta with the Arca granosa shells at low hill slope (at about 10-15 m in height) and grounds of the Arca granosa (which live in the sea shore) with the Placura suggesting tsunami deposits (C¹⁴ age of 4,500-4,300 years). The highest sea level at 4,600-4,500 was marked at 3-4 m in height by the wave cut-off and layers of oysters, gastropods with rock fragments in the same level and at the same time.

- Maybe, there were 3 tsunamis happening at 4,500-4,300, 4,100-3,900 and 900-600 years in the studied area.

Người biên tập: PGS. TSKH. Nguyễn Địch Dỹ.