As the supercontinent Rodinia was assembling ca. 1.1 billion years ago, there was extensive magmatism on at least five Proterozoic continents including the development of the North American Midcontinent Rift. New paleomagnetic data from 84 lava flows of the Osler Volcanic Group of the Midcontinent Rift reveal that there was a significant and progressive decrease in inclination between the initiation of extrusive volcanism in the region (ca. 1110 Ma) and ca. 1105 ± 2 Ma (during the “early stage” of rift development). Paleomagnetic poles can be calculated for the lower portion of the reversed Osler Volcanic Group (40.9°N, 218.6°E, A95 = 4.8°, N = 30) and the upper portion of the reversed Osler Volcanic Group (42.5°N, 201.6°E, A95 = 3.7°, N = 59; this pole can be assigned the age of ca. 1105 ± 2 Ma). This result is a positive test of the hypothesis that there was significant plate motion during the early stage of rift development. In addition to being a time of widespread volcanism on Laurentia and other continents, this interval of the late Mesoproterozoic was characterized by rapid paleogeographic change.

The 2014_Osler_data folder contains these files: Simpson_Island_alldata.xlsx: This excel spreadsheet has all of the specimen level data and details the flow mean calculations. SimpsonIsland_OslerData.csv: This csv file contains the flow (i.e. site) mean paleomagnetic data as well as the locations of the flows stratigraphically and geographically (lat, long is in WGS84). Halls1974_data.csv: This csv file contains data from the Halls (1974) study of the Osler Volcanics. Tauxe2009a_data.csv: This csv file contains data from the Tauxe and Kodama (2009) study of the North Shore Volcanic Group. The 2014_Osler_Manuscript folder contains the manuscript and figure files. The source .tex file and individual figure files are in the folder along with the compiled .pdf file. The 2014_Osler_Code folder contains an IPython notebook with all of the statistical data analysis and plotting for the manuscript. In addition to the IPython notebook, the folder contains the pmag.py, and pmagplotlib.py libraries of PmagPy version 2.206 as well as a newly developed library IPmag.py that modifies some of the interactive programs of PmagPy for use in the IPython environment in addition to providing new functions. This folder also contains a PDF version of notebook to be viewed outside of the IPython that is the supporting online material to the G^3 manuscript. Note that the IPython notebook can also be viewed online as rendered html without an IPython installation at this link: http://nbviewer.ipython.org/urls/raw.github.com/Swanson-H...