GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 279-4
Presentation Time: 8:45 AM


SMITH IV, James Emerson, Colorado School of Mines, Chevron Center of Research Excellence, 1516 Illinois Street, Golden, CO 80401, BENTLEY, Samuel J., Geology and Geophysics, LSU, Baton Rouge, LA 70803, SNEDDEN, Gregg, U.S. Geological Survey, P.O. Box 25098, Baton Rouge, LA 70894 and WHITE, Crawford, Coastal Studies Institute, Louisiana State University, Baton Rouge, LA 70803,

The Mississippi River Delta has undergone tremendous land loss over the past century due to natural and anthropogenic influences, a fate shared by many river deltas globally. A globally unprecedented effort to restore and sustain the remaining subaerial portions of the delta is now underway, an endeavor that is expected to cost $50-100B over the next 50 yr. Success of this effort requires a thorough understanding of natural and anthropogenic controls on sediment supply, accumulation, and delta geomorphology. In the Mississippi River Delta, hurricanes have been paradoxically identified as both agents of widespread land loss, and positive influences for marsh vertical sediment accretion. We present the first multi-decadal chronostratigraphic assessment of sediment supply for a major coastal basin of the Mississippi River Delta that assesses both fluvial and hurricane-induced contributions to sediment accumulation in deltaic wetlands. Twenty seven cores have been analyzed for radioisotope geochronology and organic content to establish the chronology of mineral sediment supply to the wetlands over the past ~70 years. Our findings indicate that over multi-decadal timescales, hurricane-induced sediment delivery may be an important contributor for deltaic wetland vertical accretion, but the contribution from hurricanes to long-term sediment accumulation is substantially less than sediment delivery supplied by existing and planned river-sediment diversions at present-day river-sediment loads.