La Brea tar pits in California are the result of ancient oil seepages and famous for the fossils of extinct animals which were trapped in the tar. The asphalt lakes in Trinidad and Venezuela are also the result of ancient oil seepages. Have fossils of any kind been found in either of them, and if not, why not?
Quite an oddity sits in La Brea in South Trinidad—the world's largest asphalt lake. Pitch Lake, while perhaps not the most beautiful of nature's creations, is certainly an intriguing one. The 100-acre lake is believed to be 250 feet deep in the center and contains some 10 million tons of pitch. As the lake replenishes itself and turns over, artifacts both peculiar and historically significant such as a mastodon tooth, fossil remains of the giant sloth, and Amerindian artifacts have been uncovered. Mineral pools on the lake are purported to have healing properties because of their high sulphur content.
One example from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6097493/ is an article with the title
Fossil snakes (Squamata, Serpentes) from the tar pits of Venezuela: taxonomic, palaeoenvironmental, and palaeobiogeographical implications for the North of South America during the Cenozoic/Quaternary boundary
yes, fossils have been found