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Prefolding and premegakinking magnetizations from the Devonian Comerong Volcanics, New South Wales, Australia, and their bearing on the Gondwana Pole Path
Author(s) -
Schmidt P. W.,
Embleton B. J. J.,
Cudahy T. J.,
Powell C. McA.
Publication year - 1986
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/tc005i001p00135
Subject(s) - geology , craton , devonian , paleontology , paleomagnetism , carboniferous , syncline , apparent polar wander , volcanic rock , terrane , gondwana , tectonics , volcano , structural basin
Palaeomagnetic results from the late Middle to early Late Devonian Comerong Volcanics in the Budawang Synclinorium, Lachlan Fold Belt (LFB), New South Wales, Australia, satisfy a fold test and support the hypothesis that foliated parts of the LFB have been folded by megakinks during the terminal mid‐Carboniferous orogenic phase. The preferred pole position is at 76.9°S, 330.7°E (A 95 = 7.2°), allowing calibration of the Australian pole path at around 370 Ma ago. An alterative pole position at 71.3°S 283.1°E (same A 95 ) takes into account a possible rotation of the megakinked terrane by 15° clockwise with respect to the Australian craton. Although there are still problems unravelling previously published results from Silurian rocks in the LFB, both because of unreliability and uncertainty as to where the LFB crustal units lay in relation to the Australian craton, there is no geological reason to suspect any large relative movement between the LFB and the craton since the Middle Devonian, and thus the Comerong Volcanics pole position is representative of the Late Devonian for Australia. The new pole requires reassessment of many other poles that have previously been accepted as representing the Siluro‐Devonian for Australia, and Gondwanaland. We present reasons for believing that the magnetization, or remagnetization of many rock units (e.g., Mereenie Sandstone and Mulga Downs Group, Australia, and the Gneigura Supergroup, Africa) was later than sedimentation, probably during widespread Early Carboniferous deformation. Another rock unit (Msissi Norite, Africa) could be of Early Carboniferous, rather than Late Devonian, age.