Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum
James C. Zachos,1*
Ursula Röhl,2
Stephen A. Schellenberg,3
Appy Sluijs,4
David A. Hodell,6
Daniel C. Kelly,7
Ellen Thomas,8,9
Micah Nicolo,10
Isabella Raffi,11
Lucas J. Lourens,5
Heather McCarren,1
Dick Kroon12
The Paleocene-Eocene thermal maximum (PETM) has been attributed to the rapid release of 
2000 x 109 metric tons of carbon in the form of methane. In theory, oxidation and ocean absorption of this carbon should have lowered deep-sea pH, thereby triggering a rapid (<10,000-year) shoaling of the calcite compensation depth (CCD), followed by gradual recovery. Here we present geochemical data from five new South Atlantic deep-sea sections that constrain the timing and extent of massive sea-floor carbonate dissolution coincident with the PETM. The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years). These findings indicate that a large mass of carbon (»2000 x 109 metric tons of carbon) dissolved in the ocean at the Paleocene-Eocene boundary and that permanent sequestration of this carbon occurred through silicate weathering feedback.
1 Earth Sciences Department, Earth and Marine Sciences Building, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
2 Deutsche Forschungs-gemeinschaft (DFG) Research Center for Ocean Margins, University of Bremen, Leobener Strasse, 28359 Bremen, Germany.
3 Department of Geological Sciences, San Diego State University, 5500 Campanile Drive, San Diego CA 92182–1020, USA.
4 Laboratory of Palaeobotany and Palynology, Department of Palaeo-ecology; Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
5 Faculty of Geosciences, Department of Earth Sciences; Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
6 Department of Geological Sciences, University of Florida, 241 Williamson Hall, Post Office Box 112120, Gainesville, FL 32611, USA.
7 Department of Geology and Geophysics, University of Wisconsin, Madison, 1215 West Dayton Street, Madison, WI 53706, USA.
8 Wesleyan University, 265 Church Street, Middletown, CT 06459–0139, USA.
9 Department of Geology and Geophysics, Yale University, New Haven, CT 06520–8109, USA.
10 Department of Earth Science, Rice University, 6100 Main Street, MS-126, Houston, TX 77005–1892, USA.
11 Dipartimento di Scienze della Terra, Universitario G. D'Annunzio, Campus Universitario, Via dei Vestini 31, 66013 Chieti Scalo, Italy.
12 Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, HV 1081 Amsterdam, Netherlands.
* To whom correspondence should be addressed. E-mail: jzachos{at}emerald.uscs.edu
