Evolutionary palaeoecology of Cainozoic foraminifera: Tethys, Indo-Pacific, Southern Australasia

Abstract

There were four major coolings and several other well-marked steps in global environmental change during the Cainozoic era, providing a physical framework against which to set various fossil successions in the three environmental realms (neritic, pelagic, terrestrial). The Tethyan large neritic foraminifera are unified by having possessed photosymbionts, evolving and spreading in a self-organizing way through the oligotrophic euphotic zone. Progressive evolution, driven by K-selection, was curtailed episodically by physical perturbation acting through nutrient pollution. The outcome was a succession of chronofaunas at a scale of 106-107 years. Tropical Indo-Pacific faunas have not been studied to the same degree but show numerous parallels with Tethys. Chronofaunal turnovers occured at the end of the Maastrichtian, in the late Bartonian, and at the ends of the Priabonian and Langhian. Indo-Pacific faunas display parallels with southern temperate patterns at the edge of the province, where immigrations mark provincial latitudinal expansion during global warmings. Also at the southern edge of the Indo-Pacific province, the New Zealand benthic succession shows a strongly pulsing taxic turnover, in which peaks correlate with warm immigrations. Mature photosymbiotic communities are inherently fragile and vulnerable to instability during warming, transgression, and expansion of the trophic resource continuum. Physical perturbations have greater impact on mature communities than on less mature communities, but are seen simultaneously defining other chronofaunas.