PETROGRAPHIC ANALYSIS OF VEGEMORPHS FROM ELEUTHERA, THE BAHAMAS

In The Bahamas, vegemorphs, or rhizoliths, are fossil plant or root traces found in fossilized dunes, especially regressive dunes. Specifically, vegemorphs occur in the Cockburn Town Member of the Grotto Beach Formation. This study focused on comparing cementation content and extent of vertical vegemorphs compared to horizontal vegemorphs found on Eleuthera, The Bahamas. Two hypotheses exist about vegemorph formation: 1) percolation of meteoric water leading to cementation and 2) rapid burial and subsequent organic decay during dune formation. Percolation of meteoric water implies that rapid flow routes (vertical vegemorphs) should contain more cement than slow flow routes (horizontal vegemorphs). The degree of cementation between two samples were compared using point counts. Both samples contained abundant laminated, micritized soil crust (calcrete) within the void previously occupied by plant material. However, no significant difference exists in cementation between vertical and horizontal vegemorph samples. This pilot study suggests that these vegemorphs formed by rapid burial and organic decay during dune formation.