Very high energy sedimentation (supratidal hurricane deposits) and Mid-Holocene highstand on carbonate platforms, Andros, Bahamas: An alternative view

• Published in: Sedimentary geology 2007-07, Vol.199 (1), p.29-49
• Main Author: Bourrouilh-Le Jan, Françoise G.
• Format: Article
• Language: English
• Subjects: Bahamas; Holocene; Hurricanes; Marine; Sea-level highstand
• ISSN: 0037-0738
• DOI: 10.1016/j.sedgeo.2005.12.032

Twenty-eight 14C dates were obtained from 90 cores drilled through the tidal flats of western Andros Island, a large area (2000 km 2), mostly covered by mangroves and stromatolitic deposits. These dates are correlated with location of the samples, sedimentological description, position of the samples at the time of deposition and their present-day sedimentological position. Measurements were made on bulk algal sediments and location of the relative paleo-sea-level is inferred from paleobathymetric reconstructions. On the basis of 14C dates, I conclude that the whole area was flooded about 5000 years BP and then was covered by the subtidal greyish mud facies, rich in Peneroplids, in the area of Deep Creek (north of the study area), Pelican Creek and Wide Opening (southeast of the study area). The level of this paleo-Great Bahama Bank Sea continued to rise until 3500 years BP and then slowly fell asymptotically toward the present-day level. Thick hurricane marks (aragonitic lime mud with Didemnids spicules, several cm thick), previously defined as hurricane trails, can be observed throughout the cores, from 2000 years BP onwards. From 2000 years BP onwards it seems that the modern physiography was already established, including tidal estuaries, channels and stromatolite-bearing swamps. Paleogeographic maps and sections have been drawn, and accumulation rates calculated in the various sedimentological zones of the tidal flats of western Andros. These vary between 0.5 to 0.04 mm/yr. The modern topography of the tidal flats was established by 2000 years BP; similarly, the modern geological features, controlled by a tropical climate strictly dependent on hurricanes, were already established by 2000 years BP and seem to have been initiated between 2500 and 2000 years BP.