machari formation
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2015 ◽  
Vol 89 (3) ◽  
pp. 377-384 ◽  
Author(s):  
Paul S. Hong ◽  
Duck K. Choi

AbstractThis paper reports the successive occurrence of Ptychagnostus sinicus Lu, 1957 and Ptychagnostus atavus (Tullberg, 1880) from the lower part of the Machari Formation, Yeongwol Group, Korea. Morphometric approaches of using the landmark and principal component analyses make it possible to differentiate P. sinicus from P. atavus with clarity: pygidia of P. sinicus have a relatively narrow M1, a transverse F2, and a weakly developed M2 tubercle, whereas those of P. atavus are characterized by a broadly arching M1, a chevron-shaped F2, and a prominent M2 tubercle. Recognition of P. atavus, for the first time in Korea, allows the determination of the base of the Drumian Stage in Korea and aids correlation with other parts of the world.


Geobios ◽  
2008 ◽  
Vol 41 (2) ◽  
pp. 183-204 ◽  
Author(s):  
Duck K. Choi ◽  
Eun-Young Kim ◽  
Jeong Gu Lee

Geobios ◽  
2004 ◽  
Vol 37 (2) ◽  
pp. 159-189 ◽  
Author(s):  
Duck K Choi ◽  
Jeong Gu Lee ◽  
Baek Cheor Sheen

2003 ◽  
Vol 77 (5) ◽  
pp. 895-907 ◽  
Author(s):  
Paul S. Hong ◽  
Jeong Gu Lee ◽  
Duck K. Choi

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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