Silicate weathering and North Atlantic silica burial during the Paleocene-Eocene Thermal Maximum

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doi: 10.1130/G37704.1
Author(s): Penman, Donald E.
Author Affiliation(s): Primary:
Yale University, Department of Geology and Geophysics, New Haven, CT, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 44(9), p.731-734. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. GSA Data Repository item 2016239. 30 refs.; illus.
Summary: During the Paleocene-Eocene Thermal Maximum (PETM, ca. 56 Ma), thousands of gigatons of carbon were released into the ocean and atmosphere over several thousand years, offering the opportunity to study the response of ocean biogeochemistry to a carbon cycle perturbation of a similar magnitude to projected anthropogenic CO2 release. PETM scenarios typically invoke accelerated chemical weathering of terrestrial silicate rocks as a significant negative feedback driving the recovery and termination of the event. However, the implications of this mechanism for the geochemical cycling of silica during the PETM have received little attention. I use "back-of-the-envelope" calculations and a simple two-box geochemical model of the marine silica cycle to demonstrate that the sequestration of thousands of gigatons of carbon by enhanced silicate weathering during the PETM would have dramatically increased the riverine supply of dissolved silica (H4SiO4) to the oceans. This would have elevated seawater [H4SiO4], encouraging both increased opal (SiO2) production by siliceous organisms and enhanced preservation of SiO2 in the water column and sediments. Both of these factors would have promoted a prompt (due to the relatively short oceanic residence time of silica) increase in sedimentary opal burial, thus balancing the marine silica budget. Several recently recovered deep-sea sedimentary records from the central North Atlantic demonstrate elevated SiO2 content across the Paleocene-Eocene boundary, which I argue is the result of enhanced production and/or preservation of SiO2 in response to elevated [H4SiO4] in the North Atlantic, representing the ultimate fate of excess Si weathered from the continents during the PETM.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Burial; Carbon; Carbon cycle; Cenozoic; Chemically precipitated rocks; Chert; Climate effects; Cores; Expedition 342; Framework silicates; Geochemical cycle; IODP Site U1403; IODP Site U1408; IODP Site U1409; Integrated Ocean Drilling Program; Lithofacies; Marine environment; Models; North Atlantic; Opal; Paleo-oceanography; Paleocene-Eocene Thermal Maximum; Paleoclimatology; Paleogene; Sea water; Sedimentary rocks; Silica; Silica minerals; Silicates; Silicic acid; Tertiary; Weathering
Coordinates: N395636 N395636 W0514811 W0514812
N412617 N412618 W0494708 W0494709
N411744 N411745 W0491359 W0491400
Record ID: 2016083469
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