Late Neoproterozoic to Early Palaeozoic palaeogeography of Avalonia: some palaeomagnetic constraints from Nuneaton, central England

Abstract

Palaeomagnetic studies have been carried out on Neoproterozoic, Cambrian and Ordovician rocks in the Nuneaton inlier, England (52.5 • N, 1.5 • W). Three magnetic components were recognized, which provide a consistent structural and magnetic history of the inlier. Neoproterozoic volcaniclastic and intrusive rocks acquired a characteristic remanent magnetization (ChRM) dated at 603 Ma. Late Ordovician rocks are represented by lamprophyre and diorite intrusions and their ChRMs were probably imprinted during their emplacement, at about 442 Ma. The Lower Cambrian sedimentary sequence of the Hartshill Sandstone Formation, which unconformably overlies the Neoproterozoic rocks and hosts the Ordovician intrusions, does not preserve a primary magnetization but shows the imprints of the Late Ordovician (442 Ma) remagnetization, as well as a probable end-Carboniferous remagnetization. Palaeolatitudes calculated for the late Neoproterozoic rocks and Ordovician intrusions are in good agreement with other palaeolatitudes calculated for Avalonia during those times. Both the late Neoproterozoic and Late Ordovician rocks additionally show ChRMs with declination anomalies indicating a large tectonic rotation of the Nuneaton area, possibly during one of the Caledonian phases of deformation affecting southern Britain.

Peri-Gondwanan terrane interactions recorded in the Cambrian–Ordovician detrital zircon geochronology of North Wales

“…Trench and Torsvik, 1991;Torsvik et al, 1993;Piper, 1997). Notably, declination data reported by Vizan et al (2003) suggest a 165°clockwise rotation of rocks in the Midland Platform between Late Ordovician and Carboniferous, entirely consistent with the geometry shown in Fig. 11.…”

Stratigraphy, provenance and tectonic setting of the Lumsden Dam and Bluestone Quarry formations (Lower Ordovician), Halifax Group, Nova Scotia, Canada

“…Figure 11 shows a possible terrane configuration consistent with this hypothesis, based on the assumption that Megumia was located within a rift system between East and West Avalonia. This model is consistent with both the sinistral transpressional setting for the Menai Strait Fault System, with the likely initial position of Ganderia (e.g., Pollock et al 2009;van Staal et al 2012) along the Amazonian margin, and with substantial rotation of portions of Avalonia during later Paleozoic history as suggested by Vizan et al (2003).…”

Chapter 7 Neoproterozoic glacial palaeolatitudes: a global update

“…The authors of the study inferred a moderate depositional palaeolatitude from the presumably adjacent Avalonian arc: the 580-575 Ma Marystown Volcanics (see above) and the c. 603 Ma Caldecote Volcanics plus related intrusions (Vizan et al 2003). We suspect that this estimate is unreliable, given the combined uncertainties in glacial influence of the Gwna beds, palaeogeographic affinity of the Mona complex relative to the Avalonian arc, and age of the succession.…”