Paleontology and geologyPeriodic fluctuations in sea level led to the formation of alternating zones of marine and non-marine rocks and fossils. In the Early Carboniferous, algal and crinoid patch reefs grew in the warm, shallow waters of southern Kentucky, while a delta in the north deposited clays and silts into the sea. By the mid-Carboniferous, the shallow waters contained a diverse marine fauna, and therefore fossils of shark teeth, crinoids, blastoids, and the corkscrew bryozoan Archimedes are common. Erosion of the rising Appalachians in the Late Carboniferous created an extensive river delta system. Plant remains accumulated in the swampy, low-lying areas and eventually would become rich coal deposits. Plant fossils associated with coals include horsetails, ferns, and extinct gymnosperms. Terrestrial animal fossils are rare. |