Home | Archived February 20, 2019 | (i) |
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Research Vessel Marion Dufresne Cores Tampa Bay, Florida
Seismic data acquired by the University of South Florida indicate that about 16 to 17 m of sediment overlies the deepest recorded reflection in this depression. Water depth at the chosen sites is about 9 m, which gave the ship just 3 m of clearance between the hull and the bay floor. The captain of the Marion Dufresne agreed to core in just about the shallowest water depth ever attempted from this ship. (The shallowest core is believed to be from 8-m water depth in Chesapeake Bay.)
Owing to the shallow water depth, the trigger arm on the corer had to be held by hand, because the trigger weight was already on the bottom of the bay before the core barrel was released. In fact, the core barrel was already in the bottom before the core was deployed. The first core recovered 11.5 m of sediment that included marine sediment at the top, freshwater sediment in the middle, and marine sediment at the bottom of the core, suggesting that the oldest marine sediment is at least as old as the latest interglacial (stage 5, approx. 125 ka). The second core parted at a weld, and we were left with about 6.5 m of pipe sticking out of the bottom, which Chris Reich, Keith Ludwig, Rich Young, and Terry Edgar located, identified, described, and tagged the following day, July 19. Terry Kelley, Rich Young, and some commercial divers removed the pipe with a cutting torch on July 20. No sediment was recovered. The third core bent and recovered only 4.5 m of sediment, but it was from this core that Bekka Larson (Eckerd College) pulled a gastropod out of black mud in the core catcher. When we opened the cores, it was clear that this core stopped in the nonmarine section, whereas the first core had penetrated the entire freshwater sequence and terminated in the underlying marine sediment.
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in this issue:
Tampa Bay Coring North Carolina Coastal Erosion
Gulf of Mexico Teacher Workshop
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Home | Archived February 20, 2019 |