10.6084/m9.figshare.3454940.v1
Thomas H.P. Harvey
Thomas H.P.
Harvey
Mark Williams
Mark
Williams
Daniel J. Condon
Daniel J.
Condon
Philip R. Wilby
Philip R.
Wilby
David J. Siveter
David
J. Siveter
Adrian W.A. Rushton
Adrian W.A.
Rushton
Melanie J. Leng
Melanie
J. Leng
Sarah E. Gabbott
Sarah E.
Gabbott
A refined chronology for the Cambrian succession of southern Britain
Geological Society of London
2016
succession
Caerfai Bay Shales Formation dates
Ma
basal Quarry Ridge Grits
trilobite
238 U decay
Comley Sandstone Formation
Shropshire
tracer calibration
Upper Comley Sandstone Formation
Pembrokeshire
Cambrian Stages 3
Cambrian Stages 4
Geology
2016-06-21 12:27:25
Dataset
https://geolsoc.figshare.com/articles/dataset/A_refined_chronology_for_the_Cambrian_succession_of_southern_Britain/3454940
<p>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 <sup>238</sup>U 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 <sup>238</sup>U 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 <sup>238</sup>U 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.
</p>