See more from this Division: Topical Sessions
See more from this Session: Leaving Traces—Making Marks I: In Honor of H. Allen Curran
Abstract:
These two eolianite packages bracket the leading and trailing portions of individual sea-level highstands. The transgressive-phase dunes are invaded by the fresh-water lens as sea level continues to its acme, but regressive-phase dunes are not invaded by a fresh-water lens during the sea-level highstand in which they were deposited, resulting in a dissolutional porosity and permeability inequality between the two dune packages. Criteria have been developed to identify transgressive-phase and regressive-phase eolianites; however, the one with the most potential is based on plant trace fossils, variously called rhizomorphs, rhizocretions, or vegemorphs. Extensive field work has demonstrated that vegemorphs are found preferentially in regressive-phase eolianites, and that the presence of vegemorphs disrupts the fine-scale eolian bedding. Transgressive-phase eolianites have notably fewer vegemorphs, and as a consequence, exhibit undisturbed fine-scale laminations. Vegemorph presence or absence is readily observable on vertical faces, and so paleodunes exposed at sea cliffs, in quarries or road cuts, or in caves can be easily categorized as transgressive-phase or regressive-phase deposits.
See more from this Division: Topical Sessions
See more from this Session: Leaving Traces—Making Marks I: In Honor of H. Allen Curran