A refined chronology for the Cambrian succession of southern Britain.

Harvey, T. H. P. and Williams, M. and Condon, D. J. and Wilby, P. R. and Siveter, D. J. and Rushton, A. W. A. and Leng, M. J. and Gabbott, S. E. (2011) A refined chronology for the Cambrian succession of southern Britain. Journal of the Geological Society, 168 (3). pp. 705-716. DOI 10.1144/0016-76492010-031

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Abstract

Abstract: Three dated (U–Pb, zircon) ash beds from biostratigraphically constrained Avalonian successions of Shropshire (England) and Pembrokeshire (Wales) delimit the traditional ‘Lower'–‘Middle' Cambrian boundary and resolve a problematic regional correlation. In Shropshire, a date of 514.45 ± 0.36 [0.81 including tracer calibration and 238U decay constant errors] Ma from near the top of the Lower Comley Sandstone Formation provides a maximum age for the boundary between Cambrian Stages 3 and 4, and a date of 509.10 ± 0.22 [0.77 including tracer calibration and 238U decay constant errors] Ma from the basal Quarry Ridge Grits, Upper Comley Sandstone Formation, provides a minimum age for the boundary between Cambrian Stages 4 and 5 (and thus Series 2 and 3). These dates offer a calibration of early metazoan evolution by directly constraining the age of the intervening Comley Limestones, which contain diverse small shelly fossils in addition to trilobites, and also a key early occurrence of exceptional, three-dimensionally preserved arthropods. In Pembrokeshire, an ash bed from the Caerfai Bay Shales Formation dates to 519.30 ± 0.23 [0.77 including tracer calibration and 238U decay constant errors] Ma, equivalent to a horizon low in the Lower Comley Sandstone Formation of Shropshire, possibly around the level at which trilobites make their first local appearance.

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA62;
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Journal of the Geological Society
Volume: 168
Page Range: pp. 705-716
Identification Number: 10.1144/0016-76492010-031
Depositing User: Sarah Humbert
Date Deposited: 29 Jan 2011 13:05
Last Modified: 23 Jul 2013 10:00
URI: http://eprints.esc.cam.ac.uk/id/eprint/1992

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