Our work in the Umkondo Large Igneous Province (LIP) has sought to reinforce the paleomagnetic pole from the LIP through a combination of data compilation efforts and new data development (see https://github.com/Swanson-Hysell-Group/2015_Umkondo_Pole). Of particular interest is that relative positioning between the Kalahari Craton of southern Africa and Laurentia (cratonic North America for which there remain two possible interpretations.
Interpretation #1: There was a reversal during emplacement of the Umkondo Large Igneous Province from normal (southerly declinations) to reversed (northerly declinations) such that the younger sills with northerly declinations have the same polarity as the reversed polarity sites from the early magmatic stage of the Keweenawan Midcontinent Rift. This interpretation results in reconstructions wherein the Namaqua-Natal belt is oriented towards the Grenville margin of North America (interpretation #1 in Swanson-Hysell et al., 2015 and the reconstruction shown in the video below). Laurentia is blue and Kalahari is yellow.
[evp_embed_video url=”http://www.swanson-hysell.org/wp-content/uploads/2015/08/Interp_1_1140-980_Ma.mp4″ ratio=”0.8″ autoplay=”true”]
Interpretation #2: Umkondo directions with southerly declinations represent a period of reversed geomagnetic polarity that was followed by a relatively brief interval of normal polarity represented by the northerly declinations and then a reversal back to the reversed polarity that is recorded in the early magmatic stage of the Keweenawan Midcontinent Rift. This interpretation has the dominant polarity in the Umkondo LIP correlating with the reversed polarity in the Midcontinent Rift, but with the bulk of the intrusions actually being emplaced during an earlier geomagnetic polarity interval (ca. 1112 to 1109 Ma; interpretation #2 in Swanson-Hysell et al., 2015 and the reconstruction shown in the video below). Laurentia is blue and Kalahari is yellow.
[evp_embed_video url=”http://www.swanson-hysell.org/wp-content/uploads/2015/08/Interp_2_1140-980_Ma.mp4″ ratio=”0.8″ autoplay=”true”]
