ammonites
North slope of the local road 919, Gyeongsan City, close to Daegu City (Cretaceous of South Korea)

Where: South Korea (35.9° N, 128.6° E: paleocoordinates 45.4° N, 122.3° E)

• coordinate based on nearby landmark

• small collection-level geographic resolution

When: Geoncheonri Formation (Hayang Group), Albian (112.0 - 99.6 Ma)

• From the Albian, Lower Cretaceous, of the Geoncheonri Formation in Gyeongsan City near Daegu Metropolitan City, South Korea.

•The Geoncheonri Formation (ca. 800 m thick) is the uppermost formation of the Hayang Group, belonging to the Gyeongsang Supergroup. The Gyeongsang Supergroup is widely distributed in the south-eastern part of the Korean Peninsula, mainly within the Gyeongsang Basin, which is the largest sedimentary basin of the Korea. It is divided into the Shindong and Hayang Groups, mainly comprised of thick siliciclastic sequences of alluvial, fluvial and lacustrine sediments, and the Yuchon Group characterized by the dominance of volcanic rocks (Chang, 1975). The Hayang Group consists of Chilgok, Silla, Hakbong, Haman, Banyawol, Songnaedong, Chaeyaksan, and Geoncheonri formations in ascending order. The Geoncheonri Formation is conformably underlain by the Chaeyaksan Formation and overlain by the Jusasan Formation, the lowermost of the Yucheon Group... Since plant fossils were first reported in the Geoncheonri Formation in 1925, a series of paleontological study has been made with molluscs, spores and pollen, charophytes, and dinosaur footprints. Plant fossils from the Geoncheonri Formation were correlated with the Monobegawa Group and the Gyliak Series (Lower to ‘‘middle’’ Cretaceous) in Japan (Tateiwa, 1925, 1929). Yang (1978) noted that the co-occurrence of a pelecypod Trigonioides (s. s.) paucisulcatus in the Geonchonri Formation and in the Gyliakian Goshonoura Group (Cenomaian to Turonian) of Japan (Ota, 1959). However, primitive angiosperm pollen (Retimonocolpites peroreticulatus, R. sp. A, R. sp. B., and Tricolpites sp.) and other palynological features suggest that the age of the Geoncheonri Formation is Aptian to Albian (Choi, 1985, 1989). The charophytes from the Geoncheonri Formation also indicate Aptian to Albian age (Choi, 1987).

Environment/lithology: lacustrine - small; gray mudstone and siltstone

• It was in the dark gray mudstone of the lower part of the Geoncheonri Formation. ...The Geoncheonri Formation consists predominantly of dark gray interlaminated to thinly interbedded fine sandstone to siltstone and thinly laminated mudstone associated with calcareous silty mudstone, indicating shallow lacustrine deposits (Paik et al., 2000).

Size class: macrofossils

Collected by Ki-Hong Chang in 1971

Collection methods: surface (in situ), mechanical,

• KIGAM VP (Korea Institute of Geoscience and Mineral Resources, Vertebrate Paleontology Catalogue Number)

Primary reference: Y. -N. Lee. 2009. The first Mesozoic turtle from South Korea. Cretaceous Research 30:1287-1292 [R. Benson/R. Benson] more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 127741: authorized by Roger Benson, entered by Roger Benson on 23.05.2012