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SEMINAR: GEOTOPICS - Changes in Global Silicate Weathering over the Past 70 Million Years: Seawater Lithium Isotopes

From: Erica Calderon <ecalderon@rsmas.miami.edu>
Subject: SEMINAR: GEOTOPICS - Changes in Global Silicate Weathering over the Past 70 Million Years: Seawater Lithium Isotopes
Date: Mon, 29 Oct 2012 15:22:26 +0000

 

 

Changes in Global Silicate Weathering over the Past 70 Million Years:  Seawater Lithium Isotopes

 

Speaker: Dr. Philip Froelich

 

 

ABSTRACT:

 

Weathering of uplifted continental rocks consumes carbon dioxide and transports cations to

the oceans, thereby playing a critical role in controlling both long-term 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.  A new 70-million-year record of lithium

stable isotopes ( 7Li / 6Li ) in seawater is reconstructed from planktonic foraminifera. From the Paleocene

(60 million years ago) to the Present, del 7Li  rose by 9 per mil (‰), 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. This long-term increase occurred in step-wise fashion that might correlate with periods of orogeny in low latitude rain belts.  A 5‰ drop in del 7Li across the

Cretaceous-Paleogene boundary (KTB) cannot be produced by an impactor nor by Deccan trap volcanism,

suggesting large-scale and rapid continental denudation of scorched earth clays to the ocean.

 

 

Tuesday, October 30, 2012

3:30, SLAB, Library Map and Chart Room

Refreshments at 3:15 PM

 

 

 

Hope to see you all there!

 

 

Thank you,

 

Erica Calderon
Administrative Assistant
Marine & Atmospheric Chemistry/Marine Geology & Geophysics
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway

N Grovs 353/SLAB 212
Miami, FL 33149
(305)421-4662/(305)421-4192

Fax: (305) 421-4632
ecalderon@rsmas.miami.edu

http://www.rsmas.miami.edu/academics/divisions/marine-atmospheric-chemistry
http://www.rsmas.miami.edu/academics/divisions/marine-geology-geophysics