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GEOREF RECORD

Anthropogenic lead as a tracer of rock varnish growth; implications for rates of formation

Michael N. Spilde, Leslie A. Melim, Diana E. Northup and Penelope J. Boston
Anthropogenic lead as a tracer of rock varnish growth; implications for rates of formation
Geology (Boulder) (January 2013) 41 (2): 263-266

Abstract

Rock varnish is a thin dark coating best known from deserts, and is believed to grow extremely slowly. Varnish samples from near Socorro, New Mexico (United States), contain as much as 3.7% PbO, derived from nearby smelters operating from A.D. 1870 to 1931. Additional varnish, measuring as much as 4 mu m beyond the Pb-rich layer, indicates continued growth from 1931 to 2003. Comparison with other varnish confirms that the Pb is not an artifact. Based on Pb layer thickness, and the period of smelter operation, these very young rock varnishes yield growth rates of 28-639 mu m/k.y., substantially higher than previously documented fastest rates of 40 mu m/k.y. These rates imply that the average 1-2 mu m/k.y. rate for older varnish is not the active growth rate. Rather, it is a long-term value including periods of nondeposition, erosion, and active growth. Therefore, models of rock varnish formation should be reevaluated with consideration of much faster maximum growth rates.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 41
Serial Issue: 2
Title: Anthropogenic lead as a tracer of rock varnish growth; implications for rates of formation
Affiliation: University of New Mexico, Institute of Meteoritics, Albuquerque, NM, United States
Pages: 263-266
Published: 20130104
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2013-014352
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2013065
Illustration Description: illus. incl. sketch map
N38°10'00" - N38°30'00", W111°52'60" - W109°52'60"
N33°25'00" - N34°34'60", W107°42'00" - W105°55'00"
N34°00'00" - N35°45'00", W117°40'00" - W114°15'00"
Secondary Affiliation: Western Illinois University, USA, United StatesNew Mexico Institute of Mining and Technology, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201310
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