Global Mesozoic Reconstructions Using Revised Continental Data and Terrane Histories: A Progress Report

Abstract

A number of regional terrane reconstructions conflict with inferred global plate history or with data from adjacent regional studies. Global plate tectonic reconstructions have ignored terranes until recently, and as a result are over-simplified. This paper represents a progress report on an attempt to "marry" Mesozoic global plate reconstructions and terrane analysis to produce examples of a "third generation" of global plate tectonic maps. The best approach to such an endeavor involves reiterative intercomparison of all regional data amongst each other and with the evolving global model. Data conflicts within and between terranes and regions must be resolved by a system of relative reliability "weighting". For the purpose of completing a global tectonic synthesis, the most reliable and useful data are those which constrain "departure" (rift) and "arrival" (collision/accretion) times. Certain ad hoc decisions aid in the analysis; for example, plates and their terrane passengers are constrained to move at half-spreading rates of less than 20 cm/yr, and only one net vector is allowed per plate. Inspection of the maps produced for this progress report suggests the following preliminary results: 1) more than 100 terranes and microcontinents are required to explain Mesozoic tectonic history; 2) terranes were continuously added to the plate tectonic gristmill throughout the Mesozoic; 3) there were at least two major types of continental rifting operating in the Mesozoic: spalling-off of "chips off the old blocks", and late propagation of rifts into the centers of continents to produce their breakup and dispersion; 4) it may not be necessary to invoke breakup of the "Pacifica" and "Cimmerian" continents; 5) a number of large islands drifted across climate zones in the Mesozoic; and 6) it is possible to reconcile seemingly contradictory terrane histories using relative data reliability weighting, simple plate motions and normal spreading rates. These results demonstrate the applicability of "third generation" plate history analysis and mapping techniques.