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Reply: Stratigraphy, facies architecture and tectonic implications of the Upper Devonian to Lower Carboniferous Campwyn Volcanics of the northern New England Fold Belt. [Discussion by Henderson RA, Fergusson C]

By S.E. Bryan, R.J. Holcombe, C.R. Fielding and A. Cook


Henderson and Fergusson present several points of disagreement based on their earlier work (Fergusson et al. 1994) and emphasise the major differences between the two studies. Although not explicitly stated previously, we believe that paper to be fundamentally flawed in terms of basic lithological identification, stratigraphy and facies architecture. The main issue is one of contradictory volcanic rock-type identification, in which we maintain that many of the units described as mafic by Fergusson et al. (1994) are in fact silicic. We also found that at least some of the mafic to intermediate ‘volcanic’ components described belonged to younger intrusive dyke suites, some of which now have geochronologic control. These observational data underpin the respective interpretations on the volcanic sequence and architecture. A secondary ‘data’ issue arises in the sedimentology of the sequences; our more extensive palaeocurrent datasets are strongly at variance to those presented in Fergusson et al. (1994). Likewise, differences in tectonic models reflect these opposed datasets. A further issue raised, but which is not critical to the main thrust of the argument, is that of biostratigraphic control for the Campwyn Volcanics. However, we now have further constraints from U/Pb zircon geochronology (Bryan et al. in press)

Topics: earth
Year: 2004
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