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 10.1144/0016-76492010-031Full text not available from this repository.
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.
|Uncontrolled Keywords:||2011AREP; IA62;|
|Subjects:||04 - Palaeobiology|
|Divisions:||04 - Palaeobiology|
|Journal or Publication Title:||Journal of the Geological Society|
|Page Range:||pp. 705-716|
|Depositing User:||Sarah Humbert|
|Date Deposited:||29 Jan 2011 13:05|
|Last Modified:||23 Jul 2013 10:00|
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