Nakdong Formation

Nakdong Formation
Stratigraphic range: Hauterivian-Aptian ~127–118 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Shindong Group
Underlies	Hasandong Formation
Overlies	Unconformity
Thickness	~2,100 meters
Lithology
Primary	Conglomerate, Shale, sandstone
Location
Coordinates	35°36′N 128°12′E / 35.6°N 128.2°E / 35.6; 128.2
Approximate paleocoordinates	41°06′N 133°48′E / 41.1°N 133.8°E / 41.1; 133.8
Region	Gyeongsang Province
Country	South Korea
Type section
Named for	Nakdong, Sangju
Named by	Tateiwa, 1929
Nakdong Formation (South Korea)

The Nakdong Formation (Also known as the Nagdong Formation) (Korean: 낙동층; Hanja: 洛東層; RR: Nakdong-cheung) is an Lower Cretaceous (Hauterivian to Aptian) geologic formation in South Korea. It has been dated from the Hauteravian to the Aptian, between 127 Ma and 118.0 ± 2.6 Ma. It is also the lowermost formation-level stratigraphic unit of the Gyeongsang Supergroup. Plant fossils from the Nakdong Formation overlap with the floral assemblage of the older Myogok Formation and show a 'mixed type' of the Tetori-Type and the Ryoseki-Type flora present in this formation. Based on bivalve fossil records, it correlates with molluscan faunas of the Japanese Kitadani Formation and Sebayashi Formation.

Geology

The Nakdong Formation could be distinguished from the overlying Hasandong Formation by absence of red beds in the entire formation.

Based on facies shown in outcrops, the depositional setting of the formation has been changed from lower to upper: (A): Alluvial plain with tributaries, (B): Low sinuous channel system with bars, and (C): Sinuous channel system with splays and floodplains. The channel system of the upper Nakdong Formation is continuously extended to the Hasandong Formation.

Meanwhile, pond deposits are restricted in the formation, represented by dark gray shaly mudstone intervened between fluvial sandy deposits, showing a concave lower contact and planar upper contact, up to 2 meters thick. Ferns and bivalve fossils are occasionally from these sediments. Based on these characteristics, pond deposits of the Nakdong Formation represent small-sized channels or small ponds deposited over the floodplains. No evaporites or stromatolites have been recorded there.

Fossil content

Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.

See also

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with indeterminate dinosaur fossils

Footnotes

References

• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.

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