Discussion of the reply by RL Romer and U. Kroner on "Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf"

作者：Schofield David I^*; Waldron John W F; White Chris E; Barr Sandra M

来源：Canadian Journal of Earth Sciences, 2012, 49(11): 1372-1377.

DOI：10.1139/E2012-049

In their article 'Reply to the discussion by J.W.F. Waldron and C. E. White on "Geochemical signature of Ordovician Mn-rich sedimentary rocks on the Avalonian shelf"', R. L. Romer and U. Kroner reinterpret geochronological data presented by J.W.F. Waldron, D. I. Schofield, C. E. White, and S. M. Barr to imply an Ordovician, not a Cambrian, depositional age for the succession of the Harlech Dome, North Wales, and Meguma Supergroup, Nova Scotia. However, an extensive history of biostratigraphic and geological survey data refutes this interpretation and shows that the rocks are unequivocally Cambrian. Waldron et al. used the U-Pb zircon laser-ablation - multicollector - inductively coupled plasma - mass spectrometry technique primarily to provide information on sediment provenance and not depositional age. Investigation of anomalously young Pb-206/U-238 ages showed evidence of Pb loss. These data provide little constraint on depositional age and cannot be used to infer that the Harlech Grits Group is Ordovician.

• 出版日期2012-11