Paleomagnetic results indicate pre‐Permian counter‐clockwise rotation of the southern Tamworth Belt, southern New England Orogen, Australia

Abstract

[1] Visean ignimbrites from three fault-bounded blocks within the southern Tamworth Belt, southern New England Orogen, Australia, retain a prefolding high-temperature component of remanence, carried mainly by magnetite. Paleomagnetic data indicate that the southern Tamworth Belt occupied low to moderate paleolatitudes during the early Carboniferous. Normal and reversed polarities with low to moderate inclinations suggest that the steep, reverse polarity latest Carboniferous to earliest Permian overprint is absent from the high-temperature component data set. The mean characteristic remanence direction of three early to middle Visean ignimbrite flows (32 sites) from the Rouchel block is: declination (dec) = 154.2°and inclination (inc) = 38.8°(a 95 = 12.5°; k = 98.8), which corresponds to a paleo south pole at latitude 64.9°S, longitude 258.1°E (dp = 5.5°; dm = 9.2°, where dp is the angular length of the semiaxis of the ellipse of confidence of the calculated paleopole that lies along the pole to site great circle, and dm is the angular length of the semiaxis perpendicular to dp). Six middle to late Visean ignimbrite flows (29 sites) from the Gresford block retain a mean remanence of dec = 159.6°and inc = 54.1°( a 95 = 13.7°; k = 24.7), corresponding to a paleo south pole at latitude 72.8°S, longitude 228.4°E (dp = 13.4°; dm = 19.2°). Despite widespread overprinting throughout much of the Myall block, reliable information was obtained from three late Visean ignimbrite flows (five sites), with a mean direction of dec = 118.1°and inc = 42.5°(a 95 = 12.0°; k = 41.6), from which a paleo south pole of latitude 35.7°S, longitude 233.4°E (dp = 9.1°; dm = 14.7°) is calculated. The calculated paleo south poles do not fall on the early Carboniferous segment of the published apparent polar wander path for Australia and suggest that the southern Tamworth Belt has undergone significant counter-clockwise rotation relative to cratonic Australia. Inferred rotations for the Rouchel, Gresford, and Myall blocks are approximately 80°, 80°, and 120°, respectively. Stratigraphic and geological evidence suggest rotation took place between the mid-Namurian and latest Carboniferous and is thought to have resulted from sinistral strike-slip during compression at the eastern margin of Australia.

Orocline‐driven transtensional basins: Insights from the Lower Permian Manning Basin (eastern Australia)

“…Previous studies on the oroclinal structure were mainly focused on deformation in the older tectonostratigraphic units, such as the belt of early Paleozoic serpentinites [ Korsch and Harrington , ] and the Devonian‐Carboniferous fore‐arc basin and accretionary complex rocks [ Geeve et al ., ; Glen and Roberts , ; Li and Rosenbaum , ; Mochales et al ., ]. Nonetheless, the question whether the Manning Orocline exists has remained controversial [ Lennox et al ., ; Li and Rosenbaum , ; Offler et al ., ].…”

“…and the Devonian-Carboniferous fore-arc basin and accretionary complex rocks[Geeve et al, 2002;Glen and …”

Magnetic fabric constraints on oroclinal bending of the Texas and Coffs Harbour blocks: New England Orogen, eastern Australia

“…Murray et al (1987 and Lennox & Roberts (1988), in contrast, proposed Late Carboniferous (310-300 Ma) oroclinal bending associated with 400-500 km dextral strike-slip displacement. Geeve et al (2002) recently argued on stratigraphic and geological grounds for a comparable age, mid-Namurian to latest Carboniferous, for rotation of the Manning Orocline ( Fig. 1) as concluded by them from their palaeomagnetic data of the southern Tamworth Belt (Terrane).…”

Geodynamic Reconstructions of the Australides—1: Palaeozoic

“…350 Ma ago ( [3] and references therein). The Calliope back-arc must be strongly stretched or even oceanized at its southern end, because the overriding Wandilla arc can propagate inside and triggers oroclinal buckling of the New England Orogeny ( [51] and discussion in [52]; [53,54]; see rounded arrows in Figure 2q). …”