Latitudinal Trends in Cenozoic Reef Patterns and their Relationship to Climate
Abstract
Reefs, especially tropical coral reefs, are commonly thought to be highly sensitive to climate change. The relationship between Cenozoic reef distribution, as recorded in the PaleoReefs database, and palaeoclimatic change, as inferred from geological and geochemical proxies, has been tested. The focus is on the Oligocene-Miocene transition, but the entire pre-Pleistocene Cenozoic reef distribution was analyzed to put the results into a broader context. It is found that reef distribution patterns are not cross-correlated with palaeoclimate change. If anything, the global cooling trend from the Eocene to the Miocene is correlated with an increase of reef carbonate production and a latitudinal expansion of the reef belt, rather than the expected opposite. This reef - climate paradox is best explained by a combination of two end-member hypotheses: (1) a macroevolutionary shift led from an extrinsic control (i.e. climate-driven) on reef development during the early Palaeogene greenhouse, to an intrinsic control (i.e. biological adaptation to new oceanographic and nutrient conditions) in the late Palaeogene-Neogene icehouse; and (2) the deleterious effects of climatic cooling on reef building were made up by changes in oceanography that led to a reduction of equatorial upwelling, and an increase of habitat area of low-nutrient shallow-water settings favourable for zooxanthellate coral reef growth.