Earth:Jangdong Formation
| Jangdong Formation Stratigraphic range: latest Cenomanian-earliest Turonian 94 Ma | |
|---|---|
| File:Hwasun Seoyuri Tracksite.webp Geological map (a), Columnar section (b), Photographs of Hwasun Seoyuri Tracksite (c), and Pterosaur track-bearing horizon (d) | |
| Type | Geological formation |
| Underlies | Yeonhwari Formation(North) Jeokbyeok Formation(South) |
| Overlies | Manwolsan Tuff |
| Thickness | Up to 800m |
| Lithology | |
| Primary | Mudstone, Sandstone |
| Other | Tuff |
| Location | |
| Coordinates | [ ⚑ ] : 35°06′N 127°03′E / 35.10°N 127.05°E |
| Region | South Jeolla Province |
| Country | South Korea |
| Type section | |
| Named for | Jangdong, Hwasun |
| Named by | Kim and Park, 1966[1] |
  Jangdong Formation (South Korea) | |
The Jangdong Formation (Jangdong Tuff in some older literatures; Korean: 장동층; Hanja: 壯東層) is an Upper Cretaceous geologic formation in South Korea. It is part of the Neungju Basin, one of the nonmarine sedimentary basins formed in South Korea during the Cretaceous period. Over 1,500 dinosaur tracks have been discovered from the Hwasun Seoyuri Tracksite, which is part of the formation and designated as a Natural Monument of the Republic of Korea.
Geology
Among the Cretaceous sediments of the Neungju Basin, the Jangdong Formation is predominantly composed of silty mudstones and fine sandstones interbedded with pyroclastic materials, representing active volcanism in this area.[1][2]
The Jangdong Formation shows lithological variety depending on the region.[2] The lithology of the southern part of the formation is mainly composed of conglomerates, sandstones, silty mudstones, and pyroclastic breccia, and the facies association suggests an alluvial plain setting for this area. Whereas the lithology of the central and northern part of the formation is composed mainly of fine-grained sandstone to mudstone and dark gray siltstone to mudstone, with sedimentary features including mudcracks, ripples, evaporite casts and dinosaur tracks,[3] and the facies association suggests a marginal playa lake setting of this area.[2]
The age of the Jangdong Formation was initially suggested as latest Late Cretaceous (71-66 MA) based on K-Ar geochronology for volcanic clasts in the formation[4], but U-Pb ages from the Manwolsan Tuff which underlies the Jangdong Formation, and tuff bed in the middle of the Jangdong Formation shows 96 Ma and 94 Ma, indicating the age of the Jangdong Formation dates back to the boundary of Cenomanian-Turonian.[2]
Fossil records
Aside from diverse dinosaur and pterosaur tracks, and invertebrate traces associated with pterosaur tracks, a few carbonized wood and spinicaudata fossils have been found.[5]
Dinosaur and pterosaur tracks
Among 1,500 dinosaur footprints from 5 horizons at the Hwasun Seoyuri Tracksite, over 60 trackways made by theropods, sauropods, and ornithopods have been identified. Unlike other tracksites in Korea, nearly 88% of the tracks at this site are made by theropods.[6][7] The lack of bird footprints from the site possibly shows regional dominance of pterosaurs in this area.[5]
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
|---|---|---|---|---|---|---|
| cf. Magnoavipes | cf. M. isp. | Hwasun Seoyuri Tracksite | 16-22 cm long. Has wide digit diversification (80–90°).[7] Slipped footprints[8] and a trackway showing acceleration[9] have been reported in the L1 horizon. | |||
| Theropod type B | indeterminate | 20-28 cm long. Has wide digit diversification (50–60°). Similar to Ornithomimipus and Xiangxipus[7] | ||||
| Theropod type C | indeterminate | 40-55 cm long. Has wide digit diversification (50°).[7] | ||||
| Ornithopodichnus | O. isp. | L2 and L4 horizons | 12~80 cm long. Several trackways by small trackmakers in L2 show possible gregarious behavior.[10] | |||
| cf. Brontopodus | cf. B. isp. | L1, L4 and L5 horizons | Pes-only trackway from L4 present, which represents manus tracks that were overprinted by the pes.[10] | |||
| Pteraichnus | P. isp. | At least from three different horizons, all at least 20 meters above the L5 horizon. | 362 footprints | Different tracks attributed to various trackmakers, including dsungaripteroids[11], and small or juvenile azhdarchids or yet-to-be-reported group of pterosaurs.[5] |
See also
- List of dinosaur-bearing rock formations
References
- ↑ 1.0 1.1 Kim, Bong Kyun; Park, Byong Kwon (December 31, 1966). Geological Report of the Dongbok sheet (1:50,000). Seoul: Geological Survey of Korea. p. 33.
- ↑ 2.0 2.1 2.2 2.3 Lee, Hyojong; Sim, Min Sub; Choi, Taejin (1 December 2019). "Stratigraphic evolution of the northern part of the Cretaceous Neungju Basin, South Korea". Geosciences Journal 23 (6): 849–865. doi:10.1007/s12303-019-0019-6. Bibcode: 2019GescJ..23..849L.
- ↑ Paik, In Sung; Huh, Min; So, Yoon Hwan; Lee, Jeong Eun; Kim, Hyun Joo (April 2007). "Traces of evaporites in Upper Cretaceous lacustrine deposits of Korea: Origin and paleoenvironmental implications". Journal of Asian Earth Sciences 30 (1): 93–107. doi:10.1016/j.jseaes.2006.07.013. Bibcode: 2007JAESc..30...93P.
- ↑ Kim, Cheong Bin; Kang, Seong Seung (29 December 2012). "K-Ar Ages of Cretaceous Fossil Sites, Seoyuri, Hwasun, Southern Korea". Journal of the Korean Earth Science Society 33 (7): 618–626. doi:10.5467/JKESS.2012.33.7.618.
- ↑ 5.0 5.1 5.2 Jung, Jongyun; Huh, Min (July 2024). "New Pterosaur Tracks from the Hwasun Seoyuri Tracksite (Turonian) of South Korea: Implications for their Ecological Niche and Habitat". Palaeogeography, Palaeoclimatology, Palaeoecology 645. doi:10.1016/j.palaeo.2024.112218. Bibcode: 2024PPP...64512218J.
- ↑ Huh, Min; Paik, In-Sung; Chung, Chull-Hwan; Hwang, Koo-Geun; Kim, Bo-Sung (31 December 2003). "Theropod tracks from Seoyuri in Hwasun, Jeollanamdo, Korea: occurrence and paleontological significance.". Journal of the Geological Society of Korea 39 (4): 461–478. doi:10.14770/jgsk.2003.39.4.461. Bibcode: 2003JGSK...39..461H.
- ↑ 7.0 7.1 7.2 7.3 Huh, Min; Paik, In Sung; Lockley, Martin G.; Hwang, Koo Geun; Kim, Bo Seong; Kwak, Se Keon (February 2006). "Well-preserved theropod tracks from the Upper Cretaceous of Hwasun County, southwestern South Korea, and their paleobiological implications". Cretaceous Research 27 (1): 123–138. doi:10.1016/j.cretres.2005.10.003. Bibcode: 2006CrRes..27..123H.
- ↑ Hwang, Koo-Geun; Huh, Min; Paik, In-Sung (31 March 2006). "A unique trackway of small theropod from Seoyu-ri, Hwasun-gun, Jeollanam province". Journal of the Geological Society of Korea 42 (1): 69–78. doi:10.14770/jgsk.2006.42.1.69. Bibcode: 2006JGSK...42...69H.
- ↑ Kim, Bo Seong; Huh, Min (1 July 2010). "Analysis of the acceleration phase of a theropod dinosaur based on a Cretaceous trackway from Korea". Palaeogeography, Palaeoclimatology, Palaeoecology 293 (1): 1–8. doi:10.1016/j.palaeo.2010.04.020. Bibcode: 2010PPP...293....1K.
- ↑ 10.0 10.1 Lockley, Martin G.; Huh, Min; Kim, Bo Sung (January 2012). "Ornithopodichnus and Pes-Only Sauropod Trackways from the Hwasun Tracksite, Cretaceous of Korea". Ichnos 19 (1–2): 93–100. doi:10.1080/10420940.2011.625726. Bibcode: 2012Ichno..19...93L.
- ↑ Jung, Jongyun; Huh, Min; Unwin, David M.; Smyth, Robert S. H.; Hwang, Koo-Geun; Kim, Hyun-Joo; Choi, Byung-Do; Xing, Lida (23 June 2022). "Evidence for a mixed-age group in a pterosaur footprint assemblage from the early Upper Cretaceous of Korea". Scientific Reports 12 (1). doi:10.1038/s41598-022-14966-5. PMID 35739247. Bibcode: 2022NatSR..1210707J.
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