Patch-reef morphology as a proxy for Holocene sea-level variability,Northern Florida Keys,USA |
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Authors: | J C Brock M Palaseanu-Lovejoy C W Wright A Nayegandhi |
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Institution: | (1) U.S. Geological Survey, 600 4th Street South, St. Petersburg, FL 33701, USA;(2) NASA Goddard Space Flight Center, Wallops Flight Facility, Wallops Island, VA 23337, USA |
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Abstract: | A portion of the northern Florida Keys reef tract was mapped with the NASA Experimental Advanced Airborne Research Lidar (EAARL)
and the morphology of patch reefs was related to variations in Holocene sea level. Following creation of a lidar digital elevation
model (DEM), geospatial analyses delineated morphologic attributes of 1,034 patch reefs (reef depth, basal area, height, volume,
and topographic complexity). Morphometric analysis revealed two morphologically different populations of patch reefs associated
with two distinct depth intervals above and below a water depth of 7.7 m. Compared to shallow reefs, the deep reefs were smaller
in area and volume and showed no trend in topographic complexity relative to water depth. Shallow reefs were more variable
in area and volume and became flatter and less topographically complex with decreasing water depth. The knoll-like morphology
of deep reefs was interpreted as consistent with steady and relatively rapidly rising early Holocene sea level that restricted
the lateral growth of reefs. The morphology of shallow “pancake-shaped” reefs at the highest platform elevations was interpreted
as consistent with fluctuating sea level during the late Holocene. Although the ultimate cause for the morphometric depth
trends remains open to interpretation, these interpretations are compatible with a recent eustatic sea-level curve that hindcasts
fluctuating late Holocene sea level. Thus it is suggested that the morphologic differences represent two stages of reef accretion
that occurred during different sea-level conditions. |
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Keywords: | Lidar Holocene Sea-level fluctuations Patch reefs Morphology Florida Keys |
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