In a paper released today on Geological Magazine website we discuss the geological origin of agate tools found on Pedro Gonzalez Island, which were previously ascribed by archaeologists to a 6000 years old (Preceramic) human settlement in the area. Our results show that the source of the agate corresponds to ‘giant amygdales’, or ball-like features up to 40 cm in diameter. Our study suggests that the amygdales originally formed as large bubbles in submarine lavas due to volcanic interaction with soft sediment, which were later filled by agate during hydrothermal processes. We provide the first geological and geochemical characterisation of Pedro Gonzalez, which indicates that the volcanic and sedimentary rocks in this area emplaced on the submarine flanks of a volcanic island, most likely in the Miocene (approximately 20 million years ago). Like one of our previous publications, this suggests that Panama had a long history of volcanic island formation before formation of the Isthmus in more recent times.
Reference of the paper: Redwood, S.D., Buchs, D.M., Cavell, D.E., Submarine volcanic activity and giant amygdale formation along the Panama island arc as a precursor to 6,000 year old agate exploitation on Pedro Gonzalez Island. Geological Magazine, https://doi.org/10.1017/S0016756821001229, 2021.
Geological Research on the Isthmus of Panama 