Specimens of ginkgo have been found as far back as the Permian age in formations in South America to the end of the Miocene in North America. There are well known specimens from the Triassic age Chinle Formation in Arizona, but the most well-known specimens are from the Ginkgo Petrified Forest in Washington State. The ginkgo structure is very different from other woods. Under a microscope the tracheid sizes vary from very small to large in a single file. In most gymnosperms (softwoods) the tracheid sizes are very consistent in each file. Ginkgo specimens are rare in the fossil record and there have been very few complete logs found. The specimens on this website were collected between 1959 and 1964 on the military base in Yakima, Washington. There was permission given to clubs during this short span of six years. The Wanapum Basalt Formation spans the military base and the adjoining Yakima Ridge.