PROVENANCE OF BALLAST STONE USED IN EARLY 17TH CENTURY FOUNDATIONS AT JAMESTOWN, VIRGINIA
We analyzed 16 ballast stones from the James Fort site for this study: 9 andesites, 4 limestones, and 3 sandstones. Samples were analyzed using hand samples, thin sections, and whole-rock geochemistry. Andesite samples are porphyritic with 20-40% phenocrysts of plagioclase and hornblende in a glassy matrix. Samples contain 58 – 62% SiO2, ~17% Al2O3, and 6 – 7% Fe2O3 and plot as calc-alkaline medium-K andesites. The geochemistry of the Jamestown andesite ballast is similar to andesites from the Lesser Antilles particularly the islands of Martinique, Dominica, and Guadeloupe, which are known stops made by colonists en-route to Jamestown.
Limestone samples are fine- to medium-grained unsorted biosparites with abundant Halimeda, bryozoans, mollusks, and gastropods. Limestone ballast at Jamestown is similar to Pleistocene/Holocene limestones in Bermuda and likely arrived with the Deliverance and Patience, the replacement ships for the Sea Venture that was wrecked in Bermuda in 1609.
Quartzose to subarkosic sandstones were incorporated into the foundations of a timber frame building after the arrival of Lord De La Warre in 1610. A large oblong block of worked sandstone (10x15x45 cm) includes tool markings likely created with a rounded iron chisel by a series of low-angle strikes to shape the surface. The mineralogy and microstructures in the sandstones are similar to Mesozoic sandstones from the south of England. The large block may have originally been quarried and worked in Roman times, later transported to Jamestown as ballast, and then recycled in the timber frame building foundation.