PROTEROZOIC GROWTH AND EVOLUTION OF SOUTHERN LAURENTIA: VISUALIZATION AND INTERPRETATION BY DIGITAL PALEOMAPS

During the Proterozoic, Laurentia experienced significant crustal growth that began with the assembly of Archean landmasses during 2.0-1.8 Ga Trans-Hudson orogenesis and culminated with the assembly of Rodinia at ~1.0 Ga. Interpretation of the 4-D evolution of southern Laurentia during this pivotal period requires an understanding of the geometry and history of juvenile terrane accretion during several key time slices. We present a sequential look at the growth of Laurentia that highlights processes that potentially transform initially thin crust and lithospheric mantle of juvenile arcs into stable continental lithosphere. Important tectonic episodes that affected Laurentia during the Paleoproterozoic include early juvenile terrane accretion during the ~1.88-1.83 Ga Penokean orogeny, reworking of Archean (?) and Paleoproterozoic (1.84 Ga) basement within the 1.78-1.68 Ga Mojave province, and further accretion of juvenile crust during the 1.8-1.7 Ga Yavapai and 1.67-1.60 Ga Mazatzal orogenies. Addition of ~1.5-1.3 Ga juvenile crust took place in a region that now underlies much of the mid-continental U.S. from Texas through eastern Canada. Addition of juvenile Mesoproterozoic crust suggests accretion of outboard magmatic arc(s) linked temporally to ~1.45-1.35 Ga A-type back-arc magmatism that intruded and potentially stabilized the older Proterozoic provinces. Accretion of juvenile crust to southern Laurentia culminated with the 1.3-1.0 Ga Grenville orogeny: the final stage in the assembly of Rodinia prior to collapse and breakup between ~0.8 and 0.55 Ga. The IGCP 440 project is a multinational interdisciplinary effort to produce a comprehensive digital map of the Rodinia supercontinent at ca. 0.8 Ga and will include valuable supporting materials such as geochronologic and petrologic databases. In tandem with this effort, we present a series of paleomaps that illustrate the Proterozoic growth and evolution of Laurentia at key time slices. Digital assembly and incorporation of data from multiple sources is facilitated primarily within the GIS environment. Associated visualization and presentation software provides effective mediums to both distribute and preserve current views of the episodic assembly of Laurentia, while enabling future modifications as interpretations develop with the incorporation of future data and insight.