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U-Pb (LA-ICP-MS) dating of detrital zircons from Cambrian clastic rocks in Avalonia; erosion of a Neoproterozoic arc along the northern Gondwanan margin

J. Brendan Murphy, Javier Fernandez-Suarez, Teresa E. Jeffries and Robin A. Strachan
U-Pb (LA-ICP-MS) dating of detrital zircons from Cambrian clastic rocks in Avalonia; erosion of a Neoproterozoic arc along the northern Gondwanan margin
Journal of the Geological Society of London (March 2004) 161 (2): 243-254

Abstract

Most Neoproterozoic and Early Palaeozoic tectonic syntheses place Avalonia and related peri-Gondwanan terranes facing an open ocean along the northern margin of Gondwana, thereby providing important constraints for palaeocontinental reconstructions during that time interval. However, the precise location of Avalonia along the margin and its position relative to other peri-Gondwanan terranes is controversial. We present laser ablation-inductively coupled plasma mass spectrometry U-Pb data for detrital zircons from Cambrian clastic rocks in two localities in Avalonia: the Antigonish Highlands of Nova Scotia (62 analyses) and the British Midlands (55 analyses). The data from both samples are very similar, and taken together indicate an overwhelming dominance of Neoproterozoic (c. 580-680 Ma) or Early Cambrian source rocks with minor older Neoproterozoic clusters at c. 710 Ma or of Mesoproterozoic age, three Palaeoproterozoic zircons and one Archaean zircon. The zircons can all be derived from local Avalonian sources. The Neoproterozoic zircons are attributed to erosion of the underlying Avalonian arc. Mesoproterozoic and Palaeoproterozoic zircons of similar ages are also found in Avalonian Neoproterozoic clastic rocks and their presence in the Cambrian clastic rocks could represent recycling of Neoproterozoic strata and do not necessarily imply the presence of Mesoproterozoic or Palaeoproterozoic basement rocks within their respective drainage basins. Comparison with the data from the Neoproterozoic arc-related clastic sequences suggests significant differences between their respective drainage systems. Whereas the Neoproterozoic data require extensive drainage systems, the Cambrian data can be attributed to localized drainage systems. The change in drainage patterns could reflect rifting and isolation of Avalonia from Amazonia between c. 585 and 540 Ma. Alternatively, it might reflect the creation of topographical barriers along the northern Gondwanan margin, in a manner analogous to the Cenozoic rise of the Andes or the creation of the Basin-and-Range topography in the Western USA.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 161
Serial Issue: 2
Title: U-Pb (LA-ICP-MS) dating of detrital zircons from Cambrian clastic rocks in Avalonia; erosion of a Neoproterozoic arc along the northern Gondwanan margin
Affiliation: Saint Francis Xavier University, Department of Earth Sciences, Antigonish, NS, Canada
Pages: 243-254
Published: 200403
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 71
Accession Number: 2004-029049
Categories: GeochronologySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: IGCP Project No. 453
Illustration Description: illus. incl. sect., 2 tables, geol. sketch maps
N45°22'00" - N45°53'60", W62°15'00" - W61°25'60"
Secondary Affiliation: Universidad Complutense, ESP, SpainNatural History Museum, GBR, United KingdomUniversity of Portsmouth, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200409
Program Name: IGCPInternational Geological Correlation Programme
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