High palaeolatitude (Hodh, Mauritania) recovery of graptolite faunas after the Hirnantian (end Ordovician) extinction event
Underwood, Charlie J. and Deynoux, M. and Ghienne, J.F. (1998) High palaeolatitude (Hodh, Mauritania) recovery of graptolite faunas after the Hirnantian (end Ordovician) extinction event. Palaeogeography, Palaeoclimatology, Palaeoecology 142 , pp. 91-103. ISSN 0031-0182.
Marine shales directly overlying lower Hirnantian (uppermost Ordovician) glacially related sediments in Mauritania (North-West Africa) have produced a rich graptolite fauna spanning the Ordovician-Silurian boundary in an area of high palaeolatitude. The lowermost transgressive sandy shales are barren of graptolites, but overlying shales show a sudden appearance of a diverse fauna indicative of the terminal Ordovician persculptus Zone, suggesting that with improving conditions, colonisation by a relatively cold-tolerant fauna was possible. This fauna is replaced by a low diversity assemblage dominated by long ranging taxa, probably representing the basal Silurian acuminatus and atavus Zones. With the extinction of the persculptus Zone fauna, conditions were still hostile to warm water Silurian graptolites, and a Normalograptus fauna was again established. A sudden influx of fairly diverse taxa marks the base of the acinaces Zone and the establishment of a typical Lower Silurian fauna with the establishment of warmer water conditions.
|Additional Information:||C. Underwood was at the University of Liverpool when this paper was published. He is currently a Lecturer at Birkbeck.|
|Keyword(s) / Subject(s):||glaciation, graptolites, Ordovician, radiation, Silurian, West Africa|
|School:||Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences|
|Depositing User:||Charles Underwood|
|Date Deposited:||21 Mar 2005|
|Last Modified:||17 Apr 2013 12:32|
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