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Abstract:
The loss of coral reefs in the past is not well understood with a number of theories proposed for their loss and expansion. The Queensland Plateau has one of the best-established coral histories. It is known that coral reefs were first established in the Early Miocene. These reefs then disappeared between 11-6 Ma during the Late Miocene but reestablished around 3.6 Ma. The loss of the reefs has often been tied to cool nutrient rich water during the Late Miocene where as the reestablishment of the reefs have been tied to increases in warmer nutrient poor waters. This model has been used to explain the loss of corals in other parts of the globe. However, there have been questions about the d18O records this has been based on and how accurately they reflect SSTs. In this presentation, we show new TEX86 SST data from the Queensland Plateau. Our data shows, instead of cooler SSTs during the Late Miocene, warmer SSTs than the modern Coral Sea and similar temperatures than the West Pacific Warm Pool. In fact, our temperatures fall comfortably in the modern coral growth window. Furthermore, we found little evidence of increases in local nutrients during this time. All this makes it unlikely that cooler SSTs during the Late Miocene caused the loss of corals on the Queensland Plateau. Instead, the changes seem to be linked to more Pacific wide changes during this period of time. Given the modern debate about the future of coral reefs in a warmer world it is critical to understand what changes drive the loss of coral reefs in the past. Our records show that new ideas about coral loss are needed and that better paleoclimate records are needed from these critical environments.
