38 D1. Geomorphic Processes and Landscape Evolution Across Diverse Systems (Posters)

Friday, 21 March 2025
1:00 PM - 5:00 PM
Shenandoah ABC

PROVENANCE OF SANDSTONE BLOCKS FROM THE 17TH CENTURY GOVERNOR'S WELL SITE, JAMESTOWN, VIRGINIA

Paper number: 38-5
Program: Technical Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

In 1607, Jamestown, Virginia was founded and became the first permanent English settlement in the Americas. In 2023, during the excavation of a well (termed the Governor’s Well) which dates to the 1610s, archaeologists recovered ~150 kg of sandstone blocks. As Jamestown sits on the Virginia Coastal Plain and is underlain by unconsolidated sediment, the Governor’s Well sandstone could not have been locally sourced but was instead transported to Virginia, likely as ballast stone. This study’s purpose is to determine the provenance of the sandstone excavated from the Governor’s Well.

The sandstone was analyzed using hand samples, thin-sections, sieve analyses, elemental geochemistry, and U-Pb detrital zircon geochronology. The rock is a gray-brown, fine-grained, loosely consolidated quartz wacke. Sand-sized grains comprise approximately 47% of the total mass, with the matrix being primarily silt (~43%) with some clay (~10%). Grains are mostly subangular quartz, with some micaceous minerals and accessory zircon. Curved pore spaces in the rock may be evidence of plant roots and/or dissolved shells. Preliminary XRF analysis returned an elemental composition of primarily SiO2 (85.5%) with smaller amounts of Al (4.6%), and Fe as Fe2O3 (3.0%), with very little Ca as CaO (0.2%), indicating that the cement is iron.

130 detrital zircon grains were analyzed via LA-ICP mass spectroscopy and yielded a wide range of ages with the oldest zircons at 2.8 Ga and the youngest zircons between 280 - 300 Ma. The age population consists of 15% Paleozoic, 15% Ediacaran, 25% Mesoproterozoic, and 25% Paleoproterozoic grains. Major age gaps occur between 680 - 950 Ma and 2.1 - 2.6 Ga. These age distributions are remarkably similar to detrital zircon age populations in Paleogene sandstone units from southeastern England.

Most major voyages to Jamestown in its early history departed from London where the local geology is comprised of Cenozoic marine sedimentary rock that crop out in the immediate vicinity of London and the Thames estuary. Future work will focus on identifying a formation within this geographical region which best matches the data we have gathered on the Governor’s Well sandstone.

Geological Society of America Abstracts with Programs. Vol. 57, No. 2

doi: 10.1130/abs/2025SE-408918

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