Impact of the Late Miocene Cooling on the loss of coral reefs in the Central Indo-Pacific

Abstract. The Late Miocene Cooling (LMC) has been recognized as a global event in the climate record and posited as the start of modern ecosystems. Whereas shifts in modern terrestrial ecosystems around 7.0 – 5.5 Ma occur globally, little is known about changes in aquatic ecosystems. This is especially true of shallow water carbonate ecosystems, such as coral reefs, where few good proxy records exist. A “reef gap” existed during the Pliocene in the area of the Central Indo-Pacific, where reefs that had been present during the Messinian (7 – 5 Ma) drowned by the Early Pliocene (5 – 3 Ma). Here, we present a TEX₈₆^H-based sea surface temperature (SST) record for the Coral Sea, suggesting that the LMC was more pronounced than previously thought. During the LMC, the SSTs at ODP Site 811 declined by about 2 °C, and cooling lasted from 7 Ma to possibly as late as 5 Ma. This level of cooling has also been seen in other parts of the Central Indo-Pacific. Previous research showed that coral reefs across the Central Indo-Pacific experienced a major ecosystem change, leading to the collapse of the coral reefs by 5 Ma. This event led to a lack of coral reefs during the Pliocene, an event that has often been described as the “Pliocene reef gap.” The timing of the onset of this event matches the cooling in the records. This suggests that the LMC was a final stressor that provided a regional driver for the collapse of reefs and, therefore, a potential cause for the “Pliocene Coral Gap.” The relatively rapid and intense change in SST and other stressors associated with the cooling caused coral reef systems to collapse across the Central Indo-Pacific.