Collaborative Research: Investigation of a Proposed Suture Between East and West Gondwana - - An Integrated Field, Geochronologic, and Remote-Sensing Analysis In East Madagascar

Saint Louis University, Saint Louis MO

Investigators

Abstract

This project will investigate the age, structural geometry, and regional extent of a proposed geological suture (the Betsimisaraka suture) in East Madagascar, approximately 50 km wide and over 700 km long, that welds the continental fragments of East and West Gondwana. The suture hypothesis poses a fundamental challenge to the current paradigm regarding the configuration of Rodinia and its transformation to Gondwana. The objectives of this research are to determine the structural vergence, kinematics, and timing of terrane-accretion and terminal-suturing events in the critical part of the EAO that have important global-scale implications for Neoproterozoic tectonics. Research will proceed through an integrated program of geologic mapping and structural analysis, together with remote sensing analysis (Landsat TM and SIR C/X radar), U-Pb geochronology, geochemical, and radiogenic isotope (Re-Os, Sm-Nd) investigations. The structural investigations and sample collections will be made along five river transects that traverse the proposed suture. Within the proposed suture are meter-and km-scale blocks of peridotite, hartzburgite, gabbro, and basalt interpreted as relicts of the former Mozambique Ocean. Geochemical and geochronological analysis of these will place constraints on their age and origin, and provide an important test of the suture hypothesis. Structural investigations and U-Pb dating of rocks within and adjacent to the proposed suture will allow us to evaluate other critical elements of the hypothesis, and place important constraints on the configuration of continental terranes within Gondwana. TM imaging and SIR C/X radar analysis will reveal macro-scale kinematic relations and provide a basis for extrapolation of the suture to a larger scale. This work will lead to a new understanding of kinematics, age and overall structural vergence in the critical, eastern part of the EAO where strongly divergent views of its evolution are emerging. The research will involve collaboration between professional colleagues in Madagascar and the U.S., and allow for the participation and training of American and Malagasy students in field- and laboratory-based research.