Structural interpretation of the eastern Notre Dame Bay area, Newfoundland: regional post-Middle Silurian thrusting and asymmetrical folding: Discussion
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Trent, England, and was a true son of the district known as the Potteries, made internationally famous by the ceramics industry (Royal Doulton, Wedgwood), by the novels of Arnold Bennett and by the skills of its greatest footballing progeny, Sir Stanley Matthews. Ron was himself a considerable football (soccer) talent, cricketer (England Schoolboys) and accomplished rock-band drummer. In his late teens, he was torn between 'signing forms' with his beloved Stoke City F.C., signing a record deal with EMI (the 'Beatles' label) or going to university. It was his mother's wise head who argued convincingly that he should take the academic path. Ron's choice of university was Liverpool, where he excelled in the Department of Geology. He attained a first-class honors degree in geology in 1971 and was awarded the Department's P.G.H. Boswell Prize in sedimentology. Ron stayed at Liverpool for his doctoral research under the supervision of Dr. Patrick J. Brenchley. Ron's thesis, completed in the then quick time of three years, was entitled 'Geology of the south Berwyn Hills, North Wales, with particular reference to Upper Ordovician marine benthic communities' (Pickerill 1974). The Lower Palaeozoic of North Wales and the Berwyn Hills, in particular, were the first of three geographic regions in which Ron's scholarly application made its mark. Ron and Pat formed a strong student-supervisor team. Pat was a geologist with unusually broad interests in Lower Palaeozoic geology and who was the consummate field man (Donovan et al. 2011), features he shared with Ron. Pat's friends will remember him for his smile, his wise council and his deep insight, which counterbalanced Ron's sometimes more mercurial approach. There was a tale told in Liverpool of Ron and Pat appearing in 'The Stag's Head', which was round the corner from the Department of Geology (but, sadly, since demolished), just after 5.00 p.m., opening time. One found a table, pulled out an A4 pad of paper and started to write; the other bought two pints of bitter. As they supped the first taste of bitter, the writer passed the pad on to the bringer of sustenance, who carried on the writing. Backward and forward the pad of paper went, more (and more) pints were bought (and consumed), and by closing time Ron and Pat had the first handwritten draft of a joint research paper. Ron told another tale of those same times. The major Pickerill and Brenchley (1979) examination of the paleoecology of the Caradoc of the Berwyn Hills received a critical review, by a referee who did not recognize their abilities as systematists, noting that they were neither a Whittington nor a Cooper. It was Pat who calmed the pugnacious Ron down when he wanted to ask the editor who the referee was referring towas it Dick Whittington, the legendary Lord Mayor of London, and the boxer Henry Cooper?!
Trent, England, and was a true son of the district known as the Potteries, made internationally famous by the ceramics industry (Royal Doulton, Wedgwood), by the novels of Arnold Bennett and by the skills of its greatest footballing progeny, Sir Stanley Matthews. Ron was himself a considerable football (soccer) talent, cricketer (England Schoolboys) and accomplished rock-band drummer. In his late teens, he was torn between 'signing forms' with his beloved Stoke City F.C., signing a record deal with EMI (the 'Beatles' label) or going to university. It was his mother's wise head who argued convincingly that he should take the academic path. Ron's choice of university was Liverpool, where he excelled in the Department of Geology. He attained a first-class honors degree in geology in 1971 and was awarded the Department's P.G.H. Boswell Prize in sedimentology. Ron stayed at Liverpool for his doctoral research under the supervision of Dr. Patrick J. Brenchley. Ron's thesis, completed in the then quick time of three years, was entitled 'Geology of the south Berwyn Hills, North Wales, with particular reference to Upper Ordovician marine benthic communities' (Pickerill 1974). The Lower Palaeozoic of North Wales and the Berwyn Hills, in particular, were the first of three geographic regions in which Ron's scholarly application made its mark. Ron and Pat formed a strong student-supervisor team. Pat was a geologist with unusually broad interests in Lower Palaeozoic geology and who was the consummate field man (Donovan et al. 2011), features he shared with Ron. Pat's friends will remember him for his smile, his wise council and his deep insight, which counterbalanced Ron's sometimes more mercurial approach. There was a tale told in Liverpool of Ron and Pat appearing in 'The Stag's Head', which was round the corner from the Department of Geology (but, sadly, since demolished), just after 5.00 p.m., opening time. One found a table, pulled out an A4 pad of paper and started to write; the other bought two pints of bitter. As they supped the first taste of bitter, the writer passed the pad on to the bringer of sustenance, who carried on the writing. Backward and forward the pad of paper went, more (and more) pints were bought (and consumed), and by closing time Ron and Pat had the first handwritten draft of a joint research paper. Ron told another tale of those same times. The major Pickerill and Brenchley (1979) examination of the paleoecology of the Caradoc of the Berwyn Hills received a critical review, by a referee who did not recognize their abilities as systematists, noting that they were neither a Whittington nor a Cooper. It was Pat who calmed the pugnacious Ron down when he wanted to ask the editor who the referee was referring towas it Dick Whittington, the legendary Lord Mayor of London, and the boxer Henry Cooper?!
Summary The Upper Ordovician (late Caradoc-Ashgill) Point Leamington Formation is essentially composed of fine-grained, thin-bedded turbidites that accumulated in a deep marine environment below wave-base. Immediately underlying, and apparently conformable with the formation, there are about 120 m of red, red-green and grey bioturbated cherts overlain by late Llandeilo-early Caradoc black shales—these argillaceous, ‘pelagic’, sediments conformably overlie about 800 m of mafic pillow lavas and flows of the Lawrence Head Volcanics (middle Exploits Group). The Point Leamington Formation, up to 2200 m thick, together with the mainly fine-grained, thin-bedded turbidities, contain locally abundant wet-sediment deformation in horizons up to tens of metres thick, although most of the thickest horizons appear to represent multiple events. Conglomerate-filled gullies, channels and canyons occur within the finer grained Point Leamington Formation facies-associations. The formation is overlain, gradationally, by the deep-water conglomeratic Goldson Formation, interpreted as submarine canyon deposits; with the Ordovician-Silurian boundary occurring towards the top of the Point Leamington Formation or towards the base of the Goldson Formation, based on the presence of lower Llandovery corals in limestone boulders within an olistostrome near the gradational boundary between these formations. Wet-sediment deformation occurs as: (i) coherent folded layers; (ii) semi-coherent folded layers; (iii) chaotic balled or brecciated sediments; (iv) boudinaged layers; (v) faulted layers, involving normal, reverse and thrust faults, and best seen on a micro- to meso-scopic scale. Clastic dykes, other liquefaction and fluidization structures, together with convolute lamination, also occur either isolated from, or in association with, the above listed wet-sediment deformation styles. The wet-sediment deformation generally appears to be related to gravity-controlled slope failure, in surface to near-surface mass failure or at unspecified depth of burial, on a margin with a regional south to south-eastward downslope dip, although some folds may be interpreted as thrust-related (tectonic) deformation in wet sediments. The overall stratigraphy, sedimentology and structure suggests Upper Ordovician to Lower Silurian deep marine sedimentation in small fault-bounded and fault-controlled basins, some of which contained relatively coarse-grained, small-diameter, submarine fans. Regional considerations are consistent with the succession having accumulated in a thrust imbricate system, active during sedimentation, with new evidence to indicate Ashgill-Llandovery volcanism and magmatism that can be related to initial subduction followed by possible crustal extension. Sometime during the Ashgill, subduction appears to have ceased as all the intervening oceanic crust was consumed and volcanic arc activity shut down. During late Ashgill-Llandovery time, thin continental crust of the ‘Gander’ terrane to the east then underplated the ‘Dunnage Zone’, probably leading to foreland basin development, analogous to the plate tectonic processes in the Banda Arc today. Thus, there was a reversal of subduction polarity from the eastwards subduction of pre-Caradoc times, such that the remnant backarc basin became, for a while, a forearc as the wide backarc or marginal basin floored, at least in part by oceanic crust, telescoped. Contemporaneous sinistral shear appears to have been important in the late Ordovician-Silurian, during which time unspecified ‘suspect’ terranes may have slipped in and out of the Dunnage Zone. The contemporaneous Ashgill-Llandovery bimodal igneous activity can be explained by phases of crustal transtension as re-entrants in opposing plates slid past each other, followed by phases of transpression to re-activate the thrust imbricate system.
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