On-Line Reconstruction Tool

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The On-Line Reconstruction Tool allows to produce paleogeographic maps since Early Jurassic (200 Ma) in a variety of map projections. All reconstructions are based upon the rotation model of Schettino and Scotese [2004]. Each map is generated in real time, according to the reconstruction and projection parameters specified in the form. These maps show with different colors the distribution of the continental crust, the age of the ocean floor and the distribution of Large Igneous Provinces (LIPs). A legend is available in a separate window.

The rotation model includes a global model of relative motions between large plates, a set of regional scale kinematic models (e.g. Mediterranean, Southeast Asia, etc.) and a digital compilation of 259 tectonic elements of continental crust, 2074 outlines of LIPs [Coffin and Eldholm, 1994], 1031 polygons representing blocks of oceanic crust bounded by transform faults and isochrons. The LIP dataset is a modified version of the digital compilation available via anonymous ftp from the University of Texas Institute for Geophysics. Most of the 1031 elements of oceanic crust were extracted from the latest release (version 1.5) of the digital ocean floor age grid [Müller et al., 1997], using the method described by Schettino [1999a]. The remaining oceanic blocks belong to the North Atlantic and Arctic regions and were modeled according to the rotation parameters of Rowley and Lottes [1988].

The reference continent for all reconstructions is Central Africa. The changing orientation of this plate is defined with respect to a paleomagnetic reference frame. Hence, a temporal sequence of reconstruction maps will not show any net longitudinal drift of the lithosphere. The standard reconstruction times of the global model coincide with the times of the isochorns proposed by Royer et al. [1992] and correspond to magnetic anomalies A5 (10.9 Ma), A6 (20.1 Ma), A13 (33.1 Ma), A18 (40.1 Ma), A21 (47.9 Ma), A25 (55.1 Ma) ,A31 (67.7 Ma), A34 (83.5 Ma), M0 (120.4 Ma), M4 (126.7 Ma), M10 (131.9 Ma), M16 (139.6 Ma), M21 (147.7 Ma), and M25 (154.3 Ma). Any other reconstruction is obtained by interpolation (using stage poles). The geomagnetic time scales of Cande and Kent [1995] and Gradstein et al. [1994] were used respectively for anomalies younger than chron 34 (83.5 Ma) and for older times.

In order to generate a paleogeographic map, you must fill the the following form fields:

• Reconstruction Time. Type here the time (in Myrs) of the map you want to generate. Note that the highest reconstruction time is 200 Ma, because this is the limit time of the global model. If the reconstruction time coincides with one of the standard isochrons (see above), then all the space on both sides of a spreading center is filled.
• Projection Obliquity. This field allows to specify the latitude of the center of projection and is mostly used in conjunction with satellite projections. However, you may wish to generate oblique Mollweide or cylindrical projections to have a better look at polar regions.
• Longitude of Origin. This field allows to specify the longitude of the center of projection.
• Overlay LIPs. Check this box if you want to display the distribution of magmatic provinces at the reconstruction time.
• Overlay Pattern of Seafloor Spreading. Check this box if you want to display the age of the ocean floor at the reconstruction time. Note that only the presently preserved oceanic crust is shown; the crust that has been subducted since the reconstruction time is always displayed in white.
• Map Projection. Here you select one of the available map projections.

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