| Abstract: | The deep ocean appears hostile to life: dark, cold, and very little food. Food is mainly derived from primary productivity by phytoplankton in surface waters: many organisms consume it on its way down, so that <1% reaches the sea floor. Biological oceanographers (e.g., JGOF) established that there is a strong linkage (bentho-pelagic coupling) between food-producers in sun-lit surface waters and the abundance and species composition of deep-sea bottom faunas, such as these of benthic foraminifera. Both the average annual amount of organic carbon deposited to the sea floor and the seasonal variability in production are important. It is a question, however, whether such coupling was important in the Cretaceous, when deep-water temperatures averaged 8-12oC, and metabolic rates of benthos would have been much higher. If oceanic productivity had been similar to today's, benthic faunas would have appeared oligotrophic at such high temperature. In fact, they appear to be have been more eutrophic as judged from the morphology of dominant taxa, even though faunal and geochemical data suggest that Greenhouse World productivity was lower than todays. In addition, deep-sea benthic foraminifera did not show significant extinction at Cretaceous/Tertiary boundary, when surface productivity collapsed. Greenhouse-World faunas were non-analog to present faunas in morphology of taxa: common Recent deep-ocean species appeared at about the establishment of the Antarctic ice sheet (about 33.5 Ma), and have no morphological counterpart in older sediments. Species groups common in the Paleogene-Cretaceous declined after the establishment of ice sheets, to become extinct in the last few millions of years; they have no Recent morphological counterparts. These 'Greenhouse taxa' had apertural morphologies, thus probably feeding strategies, which have no modern counterpart. It thus seems as if Greenhouse World faunas are no true analogs of faunas in the present cold deep-oceans, where phytodetritus is deposited in little-altered, fresh form to the sea floor and used by opportunistic species. The lack of evidence for strong bentho-pelagic coupling in warm oceans might be explained by the existence of different processes of carbon transfer from surface to deep oceans than in cold oceans, or by a greater importance of primary productivity of food on the ocean floor itself, by chemosynthetic bacteria. We do not know which (if any, or both) of these possible answers is right, but Recent and future ODP drilling (e.g., Shatsky Rise, Paleogene transect, Walvis Ridge, Demerara Rise) can be expected to increase our understanding of the non-analog worlds of the past and gain improved insight in the transfer of organic carbon from the surface to the deep ocean, a process of major importance for understanding the fate of atmospheric CO2. |