FIGURE 2. Fossil bearing layers are primarily laminated limestones interspersed with volcanic tuffs. The K in The second North American fossil horntail wood-wasp (Hymenoptera: Siricidae) from the early Eocene Green River Formation

FIGURE 2. Fossil bearing layers are primarily laminated limestones interspersed with volcanic tuffs. The K-spar Tuff is the thickest, making it an easily recognized marker bed. Five layers produce prolific fossils, two below and three above the K-spar Tuff. The siricid wasp was found in the 18-inch Layer about six meters below the K-spar Tuff. Stratigraphic column modified from Buchheim et al (2011).