Original paper
Evidence for Givetian stage in the Mauritanian Adrar (West Africa): biostratigraphical data and palaeogeographic implications
Racheboeuf, Patrick R.; Girard, Catherine; Lethiers, Francis; Derycke, Claire; Herrera, Zarela A.; Trompette, Roland
published: 5/31/2001
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ArtNo.: ESP026003802004
Abstract
A palaeontological study of Devonian samples from the Mauritanian Adrar allows for the first time to establish the development of Givetian deposits in this part of western Africa, owing to abundant microfossils (ostracods, conodonts, vertebrate microremains). Above the Llandovery to Ludlow Silurian deposits, locally dated by graptolites, the first Devonian faunal elements recognized belong to the Polygnathus varcus zone of conodonts of the Givetian stage. Some of the highest samples may possibly belonging to the Frasnian stage. Biogeographic relationships with both the NE American Realm and the Old World Realm as well as the significance of palaeotethysian faunal elements are discussed. A new palaeogeographic scheme implying a rising of the western part of the W African shield (due to a collision) is used to explain the depositional gap between Upper Silurian and Middle Devonian deposits. Such a collision between North America and West Africa precedes the incoming of North American Givetian benthic faunal elements in the Mauritanian Adrar. The Givetian (lower Polygnathus varcus zone) part of the first Devonian faunas above the basal coarse sandy transgressive Devonian deposits strongly suggests a positive eustatic movement responsible for the North American Taghanic Onlap.