First record of Lower Silurian conodonts from South America: biostratigraphic and palaeobiogeographic implications of Llandovery conodonts in the Precordillera of Argentina
A collection of conodonts, including Dapsilodus obliquicostatus (Branson & Mehl), Distomodus cf. kentuckyensis Branson & Branson, Ozarkodina oldhamensis (Rexroad), and Panderodus sp., has been obtained from brachiopod coquinas in the lower part of the La Chilca Formation in the Precordillera...
| Published in: | Geological Magazine |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Cambridge University Press (CUP)
1999
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1017/s0016756899002290 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756899002290 |
| Summary: | A collection of conodonts, including Dapsilodus obliquicostatus (Branson & Mehl), Distomodus cf. kentuckyensis Branson & Branson, Ozarkodina oldhamensis (Rexroad), and Panderodus sp., has been obtained from brachiopod coquinas in the lower part of the La Chilca Formation in the Precordillera of west-central Argentina. This conodont fauna, the first to be recorded from the Llandovery in South America, can be referred to the D. kentuckyensis Biozone, and is interpreted to represent an interval in the middle Rhuddanian to lower Aeronian stages. This age assignment is supported by graptolite data from the lower third of the La Chilca Formation beneath the conodont-bearing interval. The brachiopods associated with the conodonts belong to the Afro-South American Realm, but include a high percentage of North Atlantic and cosmopolitan genera. The conodont taxa present are widespread in the tropical zone (Laurentia, Baltica, etc.). This suggests that the pronounced conodont faunal provicialism in the Upper Ordovician had disappeared in the Lower Silurian, where high- and low-latitude conodont faunas appear to be closely similar. |
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