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Earth Under Global Cooling
09 April 2009
Geological Society of America, The (GSA)
Thirty-four-million years ago, Earth changed profoundly. What happened, and how were Earth's animals, plants, oceans, and climate affected? Focusing on the end of the Eocene epoch and the Eocene-Oligocene transition, a critical but very brief interval in Earth's history, GSA's latest Special Paper provides new answers to these questions.
According to the book's editors, Christian Koeberl of the University of Vienna and Alessandro Montanari of the Observatorio Geologico di Coldigioco in Italy, the end of the Eocene and the Eocene-Oligocene (E-O) transition mark the most profound oceanographic and climatic changes of the past 50 million years of Earth's history.
Earth experienced global cooling beginning in the middle Eocene, with a sharp temperature drop of about two degrees Celsius in the Late Eocene. This drop was characterized by an increase in marine oxygen isotope values and significant floral and faunal turnovers. The global climate changes are commonly attributed to the expansion of the Antarctic ice cap following its gradual isolation from other continental masses. However, as examined in this volume, multiple extraterrestrial bolide impacts, possibly related to a comet shower that lasted more than two million years, may have played an important role in deteriorating the global climate.
The volume provides an excellent overview of conditions on Earth during the last few million years of the Eocene and around the time of the Eocene-Oligocene boundary. Chapters include an expanded look at Earth across time by Walter Alvarez and colleagues; an updated and enhanced understanding of the Eocene-Oligocene boundary transition using different climate proxies, improved time control, and climate models; integrated stratigraphy of the late Eocene-early Oligocene transition and reevaluation of the Global Stratotype Section and Point (GSSP); paleoecology and paleoclimate through the critical period of transition from hothouse to icehouse; and Late Eocene impact processes and impact stratigraphy.