The Geology Department at Macalester College is committed to collaborative
faculty-student research. To this end, many of our majors complete senior
honors theses. A typical thesis-related research experience includes one
or more summers of data collection and analysis (often in far-off places such
as Crete, Zimbabwe, Mexico, Montana, Madagascar, and even southwestern Minnesota),
followed by an oral defense and submission of a thesis to the library. In recent
years, our students have conducted projects that focus on structural geology,
geochemistry, paleontology, and sedimentology/stratigraphy.
The general requirements to participate in the Honors program may be found by clicking
here.
Michelle M. Casey
Advisor: Ray Rogers
Senior Honors Thesis: 2003
Magnetostratigraphy of the Upper Cretaceous Maevarano and Berivotra Formations,
Mahajanga Basin, Northwestern Madagascar
The Maevarano Formation and overlying Berivotra Formation cap the Upper Cretaceous
section in the central Mahajanga Basin in northwestern Madagascar. The Berivotra
Formation, which is marine in origin, yields an assemblage of fossils consistent
with a Maastrichtian age (~65Ma). The age of the Maevarano Formation is presently
based on correlation with the Berivotra Formation. In an effort to test and further
refine the current age interpretations I analyzed the paleomagnetic signal from a
suite of samples collected from both formations using alternating field demagnetization.
The results show a long interval of normal polarity followed by a single reversal
located in the uppermost part of the Berivotra Formation. This simple pattern could
place this stratigraphic section any number of places within the global polarity time
scale, but fortunately the Cretaceous-Tertiary Boundary provides an independent datum
in the local section. Preliminary results of this magnetostratigraphic analysis
suggest that the Berivotra Formation and the underlying Maevarano Formation are late
Maastrichtian in age. Additional samples throughout the Maevarano and Berivotra
Formations as well as a conglomerate test are needed to test the validity of this interpretation.
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Comments and questions to Thole@macalester.edu
