gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1998.62A.2.274 A Field Study of the Chemical Weathering of Ancient Sedimentary Organic Matter Petsch S. T. Berner R. A. Dept. of Geology and Geophysics, Yale University, New Haven, CT 06520, USA Eglinton T. I. Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA 1998 62A 2 1163 1164 Copyright © 1998, The Mineralogical Society 1998