in the eastern area, the amber-bearing sediments in the approximately 100 m thick Yanigua Formation are composed of organically rich laminated sand, sandy clay, and some intercalated lignite layers up to 1.5 m thick. Amber pieces occur in the lignite and the sandy clay. In addition to indicative
sedimentary features, the characteristics of the invertebrate and vertebrate fossils from these beds—crocodiles, sirenians, and turtles—imply that deposition occurred in a near-shore context, probably in coastal lagoons fronting low, densely forested hills (Brouwer and Brouwer, 1982).