Lithium isotope history of Cenozoic seawater; changes in silicate weathering and reverse weathering

Online Access: Get full text
doi: 10.1126/science.1214697
Author(s): Misra, Sambuddha; Froelich, Philip N.
Author Affiliation(s): Primary:
Florida State University, National High Magnetic Field Laboratory, Tallahassee, FL, United States
Other:
Froelich Education Services, United States
Volume Title: Science
Source: Science, 335(6070), p.818-823. Publisher: American Association for the Advancement of Science, Washington, DC, United States. ISSN: 0036-8075 CODEN: SCIEAS
Note: In English. Supplemental information/data is available in the online version of this article; related article by Paytan, A., on p. 810-811. 54 refs.; illus., incl. 1 table, sketch map
Summary: Weathering of uplifted continental rocks consumes carbon dioxide and transports cations to the oceans, thereby playing a critical role in controlling both seawater chemistry and climate. However, there are few archives of seawater chemical change that reveal shifts in global tectonic forces connecting Earth ocean-climate processes. We present a 68-million-year record of lithium isotopes in seawater (δ7LiSW) reconstructed from planktonic foraminifera. From the Paleocene (60 million years ago) to the present, δ7LiSW rose by 9 ppm, requiring large changes in continental weathering and seafloor reverse weathering that are consistent with increased tectonic uplift, more rapid continental denudation, increasingly incongruent continental weathering (lower chemical weathering intensity), and more rapid CO2 drawdown. A 5ppm drop in δ7LiSW across the Cretaceous-Paleogene boundary cannot be produced by an impactor or by Deccan trap volcanism, suggesting large-scale continental denudation.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Alkali metals; Atlantic Ocean; Ceara Rise; Cenozoic; Chemostratigraphy; Correlation; Cretaceous; Equatorial Atlantic; Geochemistry; Indian Ocean; Isotope ratios; Isotopes; K-T boundary; Leg 121; Leg 154; Leg 208; Li-7/Li-6; Lithium; Lower Paleocene; Mesozoic; Metals; Ninetyeast Ridge; North Atlantic; ODP Site 1262; ODP Site 1263; ODP Site 1265; ODP Site 1267; ODP Site 757; ODP Site 758; ODP Site 926; Ocean Drilling Program; Os-187/Os-186; Osmium; Paleo-oceanography; Paleocene; Paleogene; Platinum group; Radioactive isotopes; Sea water; Silicates; South Atlantic; Stable isotopes; Stratigraphic boundary; Tertiary; Upper Cretaceous; Walvis Ridge; Weathering
Coordinates: S310148 N052304 E0933525 E0873548
N034308 N092719 W0425429 W0442852
S290000 S270000 E0030000 E0013000
Record ID: 2012037638
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.