RESPONSE OF MARINE COMMUNITIES TO LATE PALEOZOIC ICE AGE CLIMATE CHANGE IN BOLIVIA

Studies of modern ecological communities demonstrate that local and regional climate change result in ecological changes; however, these studies are fundamentally limited to a small time scale and therefore cannot demonstrate the full impact of major climate change. The Late Paleozoic Ice Age (LPIA), as the last complete transition from greenhouse to icehouse conditions has a unique connection to modern climate change. By understanding the ecological response of marine invertebrate communities to the LPIA a more complete picture of the climate-faunal relationship can be established. The Copacabana Formation of Bolivia contains fossiliferous carbonates spanning the LPIA, allowing community structure from pre-glacial, glacial, and post-glacial conditions to be analyzed. Samples were collected from two localities of the Copacabana Fm., Ancoraimes and Yaurichambi, representing the early onset of glacial conditions (Late Carboniferous) and the main glaciation (Early Permian), respectively. The most abundant taxa at both sites include Kozlowskia, Phricodothyris, Stereochia, and Composita. However, the overall taxonomic composition of samples from Ancoraimes and Yaurichambi differ significantly, suggesting that changes in community structure coincide with the onset of full glaciation in the Early Permian. This difference is manifested by the appearance of typical Gondwanan cold-water taxa, such as Costatumulus, Waagenoconcha, and Hoskingia, in the younger, syn-glacial Yaurichambi samples, suggesting changes in community structure related to cooling. Additionally, Rhipidomella, Reticulariina, and Neochonetes, which are present in the Ancoraimes samples, become very rare at Yaurichambi.