Selkirkoceras in South Korea and its bearing on the Cambro-Ordovician Chosen Group.
1977; Japan Academy; Volume: 53; Issue: 3 Linguagem: Inglês
10.2183/pjab.53.90
ISSN1349-2896
Autores Tópico(s)Geotourism and Geoheritage Conservation
ResumoCambro-Ordovicianstrata called the Chosen or Joseon Group in Korea are widely distributed also in North China.In describing a copious fauna from the Machiakou limestone in its uppermost part, Grabau (1922) correlated the fauna to the Black River and perhaps Trenton of North America.Accepting this opinion I considered in 1929 the Toufangkou limestone: in Liaoning to be the Black River-Trenton equivalent.Subsequently Endo (1932) correlated his Ssuyen of Manchuria to Black River, whereas Obata (1959) was of opinion that his uppermost two stages, Tangshan and Hsiaofankechuang, in North China were coeval to the Trenton.Likewise, Chen (1976) concluded the late Middle Ordovician age of his Patou suite at the top.The above chronology was, however, mainly based on the general faunal alliance, instead of any faunal element of limited geological range.In South Korea I have first correlated the Tsuibon limestone at the top to the Machiakou limestone (1929), but later in 1937 I pointed out that the occurrence of Selkirkoceras might show the Tsuibon age to extend higher than thought before.Because a new species here described is diagnostic of the genus, the chronological problem is now taken up and reconsidered.Foerste (1929) instituted this genus with two species, Selkirkoceras cuneatum and S. tyndallense from the Selkirk limestone of the Red River formation in Manitoba, Canada.Subsequently Miller and Carrier (1942) described the latter from the Bighorn limestone, Wyoming, but Flower (1957) proposed S. bighornense for Miller and Carrier's, when he added to the genus S. burnamense from the Burnam limestone, Texas.The Red River formation, Bighorn limestone and Burnam limestone are all allocated in the Richmond stage of the Cincinnatian series in the correlation table (Twenhof el et al. 1954), but it is noted in text that conflicting opinions were expressed on their dating.In discussing the Red River fauna Foerste (1929) dated the fauna at early Richmond, provided that Mohawkian relicts were contained in it.This dating was accepted by Miller and others, but Kay and Teichert insisted their Trentonian age.While Teichert (1964) main-
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