Middle cambrian trilobites and biostratigraphy of the daegi formation (Taebaek Group) in the Seokgaejae section, Taebaeksan Basin, Korea

2007 ◽  
Vol 11 (4) ◽  
pp. 279-296 ◽  
Author(s):  
Imseong Kang ◽  
Duck K. Choi
Keyword(s):  
Middle Cambrian ◽  
Taebaeksan Basin ◽  
Taebaek Group

Late middle Cambrian (Cambrian Series 3) trilobite faunas from the lowermost part of the Sesong Formation, Korea and their correlation with North China

2013 ◽  
Vol 87 (6) ◽  
pp. 991-1003 ◽  
Author(s):  
Tae-Yoon Park ◽  
Ji-Hoon Kihm ◽  
Duck K. Choi
Keyword(s):  
North China ◽  
Abrupt Change ◽  
Middle Cambrian ◽  
Taebaeksan Basin ◽  
Late Cambrian ◽  
Lowermost Part ◽  
Taebaek Group

The Sesong Formation is a member of the Taebaek Group, Korea, which extends from late Cambrian Series 3 to middle Furongian in age. Recent studies on the trilobites of the Sesong Formation have contributed significantly to the revision of the biostratigraphy. However, trilobites in the lower part of the formation, which may include the “Stephanocare Zone”, have remained essentially overlooked since the establishment of the biozone, making it difficult to correlate with the equivalent biozones of North China. Here we report trilobite faunas from the lower part of the Sesong Formation in two different sections, the Seokgaejae and the Jikdong sections, which yield two species of Jiulongshania among other species. Species of Jiulongshania have been known to occur successively in North China, so are useful for detailed correlation. Specimens of Stephanocare richthofeni are fragmentary and rarely occur in association with Jiulongshania regularis, while Jiulongshania species occur throughout the studied intervals. Accordingly, it is reasonable to extend the previously established Jiulongshania Zone of the uppermost part of the underlying Daegi Formation into the lower part of the Sesong Formation. By doing so, the Jiulongshania Zone is correlated with the Blackwelderia Zone of North China with confidence. The lowermost part of the Sesong Formation in the Jikdong section yields a fauna including J. regularis, which implies that the boundary between the Daegi and Sesong formations is diachronous within the Taebaeksan Basin. The Daegi/Sesong formation boundary in Korea is comparable to the Zhangxia/Gushan boundary in North China in that it displays an abrupt change from a carbonate-dominant facies to a shale-dominant facies. The correlation employing the Jiulongshania species indicates that the facies shift occurred significantly earlier in Shandong, North China than in the Taebaeksan Basin, Korea.

Taebaek Group (Cambrian-Ordovician) in the Seokgaejae section, Taebaeksan Basin: a refined lower Paleozoic stratigraphy in Korea

2004 ◽  
Vol 8 (2) ◽  
pp. 125-151 ◽  
Author(s):  
Duck K. Choi ◽  
Sung Kwun Chough ◽  
Yi Kyun Kwon ◽  
Seung-Bae Lee ◽  
Jusun Woo ◽  
...  
Keyword(s):  
Lower Paleozoic ◽  
Taebaeksan Basin ◽  
Taebaek Group

Dikelocephalid trilobites from theEosaukiafauna (Upper Furongian) of the Taebaek Group, Korea

2011 ◽  
Vol 85 (2) ◽  
pp. 279-297 ◽  
Author(s):  
Seung-Bae Lee ◽  
Duck K. Choi
Keyword(s):  
South China ◽  
North China ◽  
Generic Concept ◽  
Upper Cambrian ◽  
Taebaeksan Basin ◽  
Biostratigraphic Correlation ◽  
Lowermost Part ◽  
Taebaek Group

TheEosaukiafauna is proposed for the upper Furongian trilobite assemblage from the interval spanning from the upper part of the Hwajeol Formation to the lowermost part of the Dongjeom Formation in the Taebaek Group, Taebaeksan Basin, Korea. It is characterized by the dominance of dikelocephalid trilobites comprisingEosaukia micropora, E. bella, E. acuta, Mictosaukiacf.M. globosa, andTaebaeksaukia spinatan. gen. n. sp. Taxonomic reappraisal of the genusMictosaukiathat has been employed as an upper Cambrian index taxon in eastern Gondwana reveals that more than half of the species ofMictosaukiabelong inEosaukia.This study clarifies the generic concept ofEosaukia, which provides a more reliable biostratigraphic correlation for the upper Furongian strata in eastern Gondwanan regions. TheEosaukiafauna is correlated with the“Mictosaukia”faunas from the upper Fengshanian of North China, upper Taoyuanian of South China, and upper Payntonian of Australia.

Ontogeny of the Ptychaspidid TrilobiteQuadraticephalus elongatusKobayashi, 1935 from the Furongian (Late Cambrian) Hwajeol Formation, Korea

2013 ◽  
Vol 87 (3) ◽  
pp. 379-390 ◽  
Author(s):  
Ji-Hoon Kihm ◽  
Tae-Yoon Park ◽  
Duck K. Choi
Keyword(s):  
Developmental Stage ◽  
Morphological Changes ◽  
Equilibrium Phase ◽  
Special Focus ◽  
Taebaeksan Basin ◽  
Late Cambrian ◽  
Frontal Part ◽  
Accumulation Phase ◽  
Taebaek Group ◽  
Number Of Segments

The development of the trilobite pygidium involves both an articulation process at the frontal part and the formation of new segments at the rear end, and hence the development of the meraspid pygidium entails complicated morphological changes. This study deals with the ontogeny of the Furongian (late Cambrian) ptychaspidid trilobite,Quadraticephalus elongatus(Kobayashi, 1935), from the Hwajeol Formation of the Taebaek Group, Taebaeksan Basin, Korea, with a special focus on the segmentation process during the meraspid pygidial development. Compared to the ontogeny of a ptychaspidid trilobite,Asioptychaspis subglobosa(Sun, 1924), which is assumed to be an ancestral species ofQ. elongatus, the convexity of the cranidium ofQ. elongatusincreased in a slower rate; the yoked free cheek ofQ. elongatussplits to form a ventral median suture in a later developmental stage; and, a rim-like ridge, which disappeared in the early holaspid pygidium ofA. subglobosa, was maintained in the late holaspid period ofQ. elongatus. These morphological changes with growth imply that paedomorphosis was involved in the evolution ofQ. elongatus. Eleven stages are recognized for the meraspid pygidial development, which began with an accumulation phase during which the number of segments increased from three to seven, followed by an equilibrium phase with seven segments, and ended up with a depletion phase during which the number of segments within the pygidium decreased to four. During the depletion phase, the pygidial length did not increase or even slightly decreased. The onset of the epimorphic phase, in which the total number of trunk segments does not increase anymore, precedes the onset of the holaspid period, demonstrating that the developmental mode ofQ. elongatusis protomeric.

Trilobites of thePseudokoldinioidiaFauna (Uppermost Cambrian) from the Taebaek Group, Taebaeksan Basin, Korea

2007 ◽  
Vol 81 (6) ◽  
pp. 1454-1465 ◽  
Author(s):  
Seung-Bae Lee ◽  
Duck K. Choi
Keyword(s):  
Species Diversity ◽  
South America ◽  
South China ◽  
North China ◽  
Eastern Asia ◽  
Taebaeksan Basin ◽  
Cambrian Trilobite ◽  
Taebaek Group

ThePseudokoldinioidiaFauna is a newly documented uppermost Cambrian trilobite assemblage from the Dongjeom Formation of the Taebaek Group, Taebaeksan Basin, Korea. It is characterized by low species diversity comprising six trilobite taxa:Micragnostus chiushuensis, Koldinioidia typicalis, leiostegiid genus and species indeterminate,Pseudokoldinioidia perpetis, Onychopyge borealis, and pilekiid genus and species indeterminate. Of these, special attention has been paid toPseudokoldinioidia perpetis, which was originally assigned toMissisquoia, an index fossil for the uppermost Cambrian in Laurentia.Pseudokoldinioidiais restricted to eastern Asia, whereasMissisquoiais confined to Laurentia. The appearance of thePseudokoldinioidiaFauna is interpreted as contemporaneous with the base of the‘Missisquoia’ perpetisZone of North China, which in turn is correlated with the base of theMissisquoia typicalisSubzone of Laurentia. The associatedKoldinioidiaandOnychopygemake it possible to compare thePseudokoldinioidiaFauna of Korea and North China with the latest Cambrian trilobite assemblages of South China, Australia, South America, and Mexico, and also suggests an interesting biogeographic connection among these areas in the latest Cambrian.

Trilobites from the Lejopyge armata Zone (upper Middle Cambrian) of the Machari Formation, Yongwol Group, Korea

2003 ◽  
Vol 77 (5) ◽  
pp. 895-907 ◽  
Author(s):  
Paul S. Hong ◽  
Jeong Gu Lee ◽  
Duck K. Choi
Keyword(s):  
Reference Point ◽  
Middle Cambrian ◽  
Taebaeksan Basin ◽  
Machari Formation ◽  
Stratigraphic Interval

Acid-resistant specimens of trilobites were recovered from the dissolved residues of lime mudstone collected from the lower part of the Machari Formation, Yongwol Group, Taebaeksan Basin, Korea. One of the samples yields a trilobite assemblage comprising Lejopyge armata (Linnarsson, 1869), Lisogoragnostus coreanicus n. sp., agnostid genus and species indeterminate, ammagnostid genus and species indeterminate, clavagnostid genus and species indeterminate, Cyclolorenzella sp., and Eoshengia? sp. The stratigraphic interval yielding the trilobite assemblage is herein designated as the Lejopyge armata Zone, which is correlated well with the upper Middle Cambrian biozones established elsewhere. This provides the first biostratigraphic reference point for the upper Middle Cambrian sequence of the Yongwol Group and fills partially the biostratigraphic gap between the Tonkinella (middle Middle Cambrian) and the Glyptagnostus stolidotus (uppermost Middle Cambrian) zones in the Machari Formation.

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