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Ballast Stones

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Artifact Description

The “Tortugas” shipwreck lies at a depth of 394.5-406.4m on a northwest to southeast orientation, the keel line extending along a 150º axis. When discovered the site was dominated by a low-lying mound of amorphous ballast stones, whose main nucleus extended across an area measuring 10.0 x 4.8m. The total wreckage covers 19.2m long and 15.6m wide.

The majority of the ballast mound is positioned towards the southeast two-thirds of the visible site, reflecting the requisite structural tapering of the lower hull towards the stern. The weight of the sterncastle/quarterdeck structure would have readily compensated for the lack of ballast in this part of the ship (Moore, 1991). The bows are positioned to the south. The ballast continues all the way up to the stempost.

Samples of the “Tortugas” ship’s ballast stones were examined visually by Dr. Stephen Pollock of the Department of Geosciences, University of Southern Maine, USA, followed by x-ray diffractometer analysis of six samples. The following rock forms were identified of which sandstone was the prevalent form within the hull. The analysis has not led to an identification of ballast provenance. In light of the high-volume transport of iron goods and wine stored in botijas to Cumana in Venezuela by the “Tortugas” ship (believed to be the Buen Jesús y Nuestra Señora del Rosario), and a postulated return cargo of low density tobacco, it may be hypothesized that additional ballast would have been required to be taken onboard in Venezuela.

The rock forms identified amongst the ballast stone that was analyzed are the following: Chert Nodule, Granite, Basalt, Sandstone, Quartz Sandstone, and Oolitic Limestone.


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