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Middle Miocene disruption

The "Middle Miocene disruption" refers to a wave of extinctions of terrestrial and aquatic life forms that occurred following the Miocene Climatic Optimum (18 to 16 Ma), around 14.8 to 14.5 million years ago, during the Langhian Stage of the mid-Miocene. A major and permanent cooling step occurred between 14.8 and 14.1 Ma, associated with increased production of cold Antarctic deep waters and a major expansion of the East Antarctic ice sheet. The closure of the Indonesian Throughflow, which caused an accumulation of warm water in the western Pacific that then spread eastward and reduced upwelling in the eastern Pacific, may also have been responsible. A Middle Miocene δ O increase, that is, a relative increase in the heavier isotope of oxygen, has been noted in the Pacific, the Southern Ocean and the South Atlantic. Barium and uranium became enriched in seafloor sediments.