Paper No. 120-2
Presentation Time: 8:30 AM
NEW PALEOMAGNETIC RESULTS FROM THE PALEOPROTEROZOIC KILOHIGOK BASIN, SLAVE CRATON, CANADA: IMPLICATIONS FOR THE INITIAL ASSEMBLY OF LAURENTIA
Laurentia was created by the amalgamation of six Archean cratons in Paleoproterozoic time (2.0–1.8 Ga). Quantitatively constraining the initial assembly of Laurentia hinges on robust paleomagnetic poles, especially from the Slave craton because it involves several of the earliest collisions during the amalgamation. However, published results from the Slave craton show a large (~ 110°) variance among paleopoles at 1.96–1.87 Ga, known as the Coronation loop, which has been interpreted as rapid plate motion, localized vertical-axis rotation, or true polar wander. The Rifle Formation, precisely dated at 1.963 Ga, provides a paleopole lying substantially east to the rest of the Coronation poles. Samples of that study were collected from about 30 km west of the Bathurst Fault, so large rotation of the Rifle Formation produced by the shearing of the Bathurst Fault is considered unlikely. To test the reliability of Rifle paleopole, we collected about 300 samples of the Rifle Formation and adjacent strata of the Goulburn Supergroup, in shallowly dipping autochtonous sections east of the Bathurst Fault. Magnetic mineralogy and anisotropy will be studied by various rock magnetic experiments. A paleomagnetic fold test, inverse backed contact test (on a likely Mesoproterozoic mafic dyke) and several conglomerate tests will be employed to constrain the age of remanence. A piecewise magnetostratigraphic study of the strata, including two equivalent sections of the Rifle Formation, will also help provide a time scale for the observed changes in remanence directions in order to evaluate the possibility of rapid drifting of the Slave craton or true polar wander during the amalgamation of Laurentia. Combined with recently published paleomagnetic data from Superior and Wyoming cratons, we aim to provide a new kinematic reconstruction model for the initial assembly of Laurentia.