P. M. Brück, S. G. Molyneux, 2011. "Cambrian of Ireland", A Revised Correlation of the Cambrian Rocks in the British Isles, A. W. A. Rushton, P. M. Brück, S. G. Molyneux, M. Williams, N. H. Woodcock
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As discussed in Chapter 11 of this report, some authors have considered that the uppermost part of the Southern Highland Group of the Dalradian in Scotland might be Lower Palaeozoic, possibly Early Cambrian to Early Ordovician. The age of the Irish Dalradian is also not fully clear (Daly 2001). Thus, in Ireland, strata that are clearly Cambrian in age are restricted in outcrop, being con?ned to some areas of the SE (Fig. 17) in the Leinster Terrane (Murphy et al. 1991; Woodcock 2000; Holland 2001, 2009). There they comprise the Bray and Cahore groups and part of the Lower Palaeozoic Ribband Group (Figs 18 & 19). In addition, in southernmost Leinster (Fig. 20), palynological studies have now shown that the Cullenstown Formation, which is not assigned to any of these groups, is also Cambrian. In the same area, the Ballycogly Group mylonites, which occur along the boundary between the Leinster Terrane and the Precambrian basement of the Rosslare Terrane, are considered to be Cambrian (Tietzsch-Tyler & Sleeman 1994a) although there is no direct biostratigraphical evidence.
The Leinster Terrane is made up of several sub-terranes: particulars of these and the relevant references are given in Chapter 6 of this report. Within these terranes, Brack et al. (1979) grouped the Lower Palaeozoic rocks into three belts. More recent work has shown that, as far as the Ribband Group is concerned, a fourth belt can be established (McConnell et al. 1999).
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A Revised Correlation of the Cambrian Rocks in the British Isles
This work reviews the correlation of the British and Irish Cambrian with the current (though incomplete) international standard for the Cambrian. Since the earlier edition of 1972, the basal and upper limits of the Cambrian system has been internationally agreed; so this account excludes Tremadocian rocks but includes some that were formerly considered Neoproerozoic. Half of the series and stage subdivisions are internationally agreed, but for the undefined divisions of the Cambrian the standard used here makes use of data from Avalonian successions.
Since the first edition was published, almost every aspect of the Cambrian I the British Isles has been subjected to new study. Here, the plate tectonic make-up of the British Isles is reviewed, new radiometric ages and isotopic studies are summarized and the biostratigraphy is enhanced by the study of acritarchs, especially in the Irish successions