The influence of SST on the loss and development of coral reefs in the Coral Sea from the Miocene to Pliocene

Abstract

<p>The Queensland Plateau in the Coral Sea has one of the best constrained geologic histories of coral reef expansion and demise since the early Miocene. The development coral reefs in the past is not well understood with a number of theories proposed for their loss and expansion. Coral reefs were first established in the Early Miocene in the Coral Sea. In the Late Miocene, between 11 and 7 Ma, the reef area on the Queensland Plateau declined by ~50% leading to a partial drowning and a change in platform geometry from a reef rimmed platform to a carbonate ramp. The modern atoll reefs were reestablished around 3.6 Ma although the Great Barrier Reef only developed around 0.7-0.6 Ma. The loss of the reefs has often been tied to the expansion cool nutrient rich waters in the Coral Sea during the Late Miocene. This model has been used to explain the loss and expansion of corals in other parts of the globe. However, there have been questions about the planktonic δ<sup>18</sup>O based Sea Surface Temperature (SST) records on which they are based and how accurately they reflect SSTs. Here we show new TEX<sub>86</sub> SST data from the Queensland Plateau from ODP site 811 showing temperature changes from the Late Miocene to 1 Ma. Our data shows instead of cooler SSTs during the Late Miocene in fact SSTs were warmer than the modern Coral Sea and at the upper end of the modern coral window. Therefore, it is unlikely that cooler SSTs during the Late Miocene caused the loss of corals on the Queensland Plateau. Instead, the loss seems to have been driven by the restricted growth combined with high SST driven lower growth rate and increases in subsidence at the same time among other drivers.  We also will discuss changes in the latitudinal extent of the warm pool during the late Pliocene and what caused the re-expansion of corals during this period of time.  Given the modern debate about the future of coral reefs under current climate predictive scenarios it is worth pointing out that a similar series of changes is occurring in the modern ocean.</p>