Global change at the Paleocene-Eocene boundary: Climatic and evolutionary consequences of tectonic events
Events of the Paleocene-Eocene boundary provide the clearest example to date of how a tectonic event may have global climatic onsequences. Recent advances permit well-constrained stratigraphic determination f several events that occurred at that boundary, in chron C24R: a many-fold increase in sea-f...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
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1990
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.567.7626 http://www.es.ucsc.edu/~jzachos/pubs/Rea_etal_90.pdf |
| Summary: | Events of the Paleocene-Eocene boundary provide the clearest example to date of how a tectonic event may have global climatic onsequences. Recent advances permit well-constrained stratigraphic determination f several events that occurred at that boundary, in chron C24R: a many-fold increase in sea-floor hydrothermal activity, a global warming, a reduction in the intensity of atmospheric circulation, aconversion to salinity-driven deep ocean circulation, amarked lightening of oceanic 313C values, extinction and evolution of both benthic foraminifera and land mammals, and important plate-boundary reorganizations including the outpouring of the east Greenland volcanics and the initiation of the oceanic rift between Norway and Greenland. We hypothesize that enhanced sea-floor hydrothermal ctivity occasioned by global tectonism resulted in a flooding of the atmosphere with COz, causing a reduced pole-to-equator temperature gradient and increased evaporation at low latitudes. Increased formation of warm, salty, probably low-nutrient waters coupled with the warm temperatures at high latitudes occasioned a salinity-driven, rather than temperature-driven, deep-water circulation. This newly-evolved ocean circulation pattern changed the apportionment of global heat ransport from the atmosphere tothe ocean, with concomitant changes in the circulation intensity of both. Reduced intensity of atmospheric circulation resulted in lower oceanic biological productivity and enhanced seasonality of climate on the continents. A major extinction event among benthic foraminifera was probably a response to the new low-nutrient and chemically changed bottom waters, and endemism following rapid evolution and dispersal |
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