Using palaeomagnetism to determine late Mesoproterozoic palaeogeographic history and tectonic relations of the Sinclair terrane, Namaqua orogen, Namibia

Abstract

The Sinclair terrane is an important part of the Namaqua orogenic province in southern Namibia containing well-preserved Mesoproterozoic volcano-sedimentary successions suitable for palaeomagnetic and geochronological studies. The Guperas Formation in the upper part of the Sinclair stratigraphic assemblage contains both volcanic and sedimentary rocks cut by a bimodal dyke swarm with felsic members dated herein by U–Pb on zircon at c. 1105 Ma. Guperas igneous rocks yield a pre-fold direction and palaeomagnetic pole similar to that previously reported. Guperas sedimentary rocks yield positive conglomerate and fold tests, with a maximum concentration of characteristic remanence directions at 100% untilting. The combined Guperas data generate a palaeomagnetic pole of 69.8° N, 004.1° E (A95=7.4°, N=9). The 1105 Ma post-Guperas dykes yield stable remanence directions with positive baked-contact tests and a palaeomagnetic pole at 62.3° N, 031.9° E (A95=6.9°, N=26), which is coincident with that of the Kalahari-wide Umkondo large igneous province, demonstrating tectonic coherence of the Sinclair terrane with the Kalahari craton at the time of dyke emplacement. These results show that palaeomagnetic and geochronological studies of the Sinclair terrane can provide kinematic constraints on the tectonic evolution of the Namaqua–Natal–Maud orogenic belt and its role in the formation of the Rodinia supercontinent.

Failed rifting and fast drifting: Midcontinent Rift development, Laurentia’s rapid motion and the driver of Grenvillian orogenesis

“…A more typical approach than this PEP inversion method for resolving how much of the change in pole position in a path is the result of true polar wander is to consider the APWP from other continents at the time that were not conjoined with the one of interest. Unfortunately, province (Swanson-Hysell et al, 2015), the 1105.52 ± 0.41 Ma post-Guperas dikes (Panzik et al, 2015), the <1108 ± 9 Ma Aubures Formation (Kasbohm et al, 2015) and the ≤1093 ± 7 Ma Kalkpunt Formation (Briden et al, 1979;Pettersson et al, 2007). These paleomagnetic poles all have similar positions to one another with the arc distance between the Kalkpunt Formation pole and the poles of the Umkondo large igneous province and post-Guperas dikes being less than that Belt oriented towards the Grenville margin of North America (Kasbohm et al, 2015;Swanson-Hysell et al, 2015).…”

Four-dimensional context of Earth's supercontinents

“…The Sinclair region along the western margin of Kalahari, in south-central Namibia, offers an opportunity for substantial augmentation of the Mesoproterozoic palaeomagnetic database from southern Africa. Two papers herein report new palaeomagnetic results of high quality from the youngest components of Sinclair stratigraphy: Panzik et al (2015) produce a pole that is precisely dated by U -Pb on zircons at 1105 Ma, and Kasbohm et al (2015) generate a pole from unconformably overlying redbeds, constrained in age by detrital zircons and comparison to the Kalahari apparent polar wander path. Both results conform to that Umkondo-anchored apparent polar wander path and point the way toward studies of older Sinclair strata in extending that path backward in time to envelop the Nuna-Rodinia transition.…”

Role of Paleomagnetism in the Construction of Earth’s Geographic Past

“…The field of paleomagnetism is relevant today, as scientists continue to piece together landmasses of the past to learn how the planet works (i.e., mechanisms of plate tectonics). This report's given data set is based on a study conducted in Namibia, Africa (Panzik et al, 2015). This work allowed for geophysicists to better understand the geographic formation of the earth over a billion years ago.…”

“…This is used to calculate the paleolongitudes (Equations (19) and 20). Dr. Joseph Panzik of the USF School of Geosciences provided a data set collected during the summers of 2011 and 2012 in Namibia, Africa (Panzik et al, 2015). This data set provided the declination (D) and inclination (I) values calculated on site using a magnetometer, along with the site's current latitude and longitude for each sample site (26 in total).…”