| A fossil leaf from an Oregon grape, referred to scientifically as Mahonia aguifolium. Specimen is approximately 10 million years old; it's from the early late Miocene Mehrten Formation paleobotanical locality near Columbia State Park. The Mehrten is one of three Tertiary Period geologic rock formations one can examine in California's Gold Country, western foothills of the Sierra Nevada, along the route to the upper Miocene Disaster Peak Formation plants, High Sierra Nevada; the other two are the middle Eocene Ione Formation and the late Oligocene to early Miocene Valley Springs Formation. Two supplemental localities in California's High Sierra Carson Pass area (east of Jackson, county seat of Amador County) also yield petrified woods and fossil leaves from two unnamed (in the published scientific literature) geologic rock formations of middle Miocene age. |