Mapping the Mahajanga Basin: Using GIS to Explore Spatial Relationships in Madagascar\u27s Geology and Paleontology

Tha Mahajanga Basin, located in northwestern Madagascar, is a region of intense geological and paleontological study, but has never before been subject to spatial analysis. Since 1993, expeditions conducted by Stony Brook University, Macalester College, and the University of Antananarivo have uncovered a rich sampling of more than six thousand specimens and observations including fossils of non-avian dinosaurs, crocodiles, and turtles. This paper analyzes the spatial relationships between paired groups within the fossil record as well as wider regional trends to address paleoenvironment. A combination of spatial analysis and statistics are used to determine the patterns existing between fossils or between geological features and fossil distribution. Crocodiles and turtles are tested for their significance as taphonomic controls, under the assumption that they should always co-occur in the fossil record and the absence of one may represent an unusual environmental event. Statistical analyses include correlation and goodness of fit tests to determine if significant relationships exist between the geology and paleontology in an area. Geographic Information Systems (GIS) and ClusterSeer were utilized to assess linkages between fossil groups and address questions of paleoenvironment. Findings suggest that crocodiles and turtles are more spatially and temporally correlated compared to other paired groups. In addition, body size and environmental distributions shown by the fossil record yield further insights into Madagascar\u27s late Cretaceous environment, which has wider application in Earth\u27s geologic and biologic histories