CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 12
Presentation Time: 11:00 AM

SIGNIFICANT VARIABILITY IN NORTHERN GULF COAST HURRICANE ACTIVITY ARCHIVED IN THE LATE HOLOCENE SEDIMENTS OF A FLORIDA SINKHOLE


LANE, Philip, Geology and Geophysics, Woods Hole Oceanographic Institution, 360 Woods Hole Rd., MS #2, Woods Hole, MA 02118, DONNELLY, J., Geology & Geophysics Department, Woods Hole Oceanographic Institution, MS #22, 360 Woods Hole Rd, Woods Hole, MA 02543, WOODRUFF, Jonathan, Department of Geosciences, University of Massachusetts - Amherst, 611 N. Pleasant Street, 233 Morril Science Center, Amherst, MA 01003 and HAWKES, Andrea D., Geography and Geology, University of North Carolina Wilmington, Wilmington, NC 02543, plane@mit.edu

A 4500-year record of hurricane-induced storm surges is developed from sediment cores collected from a coastal sinkhole near Apalachee Bay, Florida. Recent deposition of sand layers in the upper sediments of the pond was found to be contemporaneous with significant, historic storm surges at the site modeled using SLOSH and the Best Track, post-1851 A.D. dataset. Using the historic portion of the record for calibration, paleohurricane deposits were identified by sand content and dated using radiocarbon-based age models.

Due to the sub-decadal (~ 7 years) resolution of the record and the site’s high susceptibility to hurricane-generated storm surges, the average, local frequency of recorded events, approximately 3.9 storms per century, is greater than that of previously published paleohurricane records from the region. The high incidence of recorded events permitted a time series of local hurricane frequency during the last five millennia to be constructed. Variability in the frequency of the largest storm layers was found to be greater than what would likely occur by chance alone, with intervals of both anomalously high and low storm frequency identified. However, the rate at which smaller layers were deposited was relatively constant over the last five millennia. This may suggest that significant variability in hurricane frequency has occurred only in the highest magnitude events.

The frequency of high magnitude events peaked near 6 storms per century between 2800 and 2300 years ago. High magnitude events were relatively rare with about 0-3 storms per century occurring between 1900 and 1600 years ago and between 400 and 150 years ago. A marked decline in the number of large storm deposits, which began around 600 years ago, has persisted through present with below average frequency over the last 150 years when compared to the preceding five millennia.

Marine-indicative foraminifera, some originating at least 5 km offshore, were present in several modern and ancient storm deposits. The presence and long-term preservation of offshore foraminifera suggest that this site and others like it may yield promising microfossil-based paleohurricane reconstructions in the future.

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