Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (7) Citing Articles via Google Scholar Google Scholar Articles by Price, J. R. Articles by Patino, L. C. Search for Related Content GeoRef GeoRef Citation

Rates and time scales of clay-mineral formation by weathering in saprolitic regoliths of the southern Appalachians from geochemical mass balance

Jason R. Price^,1, Michael A. Velbel¹ and Lina C. Patino¹

¹ Department of Geological Sciences, 206 Natural Sciences Building, Michigan State University, East Lansing, Michigan 48824-1115, USA

Rates of clay formation in three watersheds located at the Coweeta Hydrologic Laboratory, western North Carolina, have been determined from solute flux-based mass balance methods. A system of mass balance equations with enough equations and unknowns to allow calculation of secondary-mineral formation rates as well as the more commonly determined primary-mineral dissolution rates was achieved by including rare earth elements (REE) in the mass balance.

Rates of clay-mineral formation determined by mass balance methods have been used to calculate the time needed for a 5% (50 g kg^–1) change in relative clay abundance in the saprolite at Coweeta; this corresponds to the "response time" of the clay mineral to, for example, a change in climate. The 5% change in relative clay abundance is the smallest change that can generally be detected using X-ray diffraction (XRD). Response times range from tens of thousands to hundreds of thousands of years. Extrapolating the Coweeta clay formation rates to other southern Appalachian regoliths, the time required to form measured clay abundances ("production times") in eastern Blue Ridge and Inner Piedmont regolith have been calculated. The production times of clay-mineral assemblages range from 2 k.y. to 2 m.y., with mean values ranging from 50 k.y. to 1 m.y. The results of this study are consistent with the arguments of Thiry (2000) that the best resolution of the paleoclimatic record in marine clay-rich sediments and mudrocks is 1 or 2 m.y.

Key Words: clays • rates • mass balance • Appalachians • regolith

This article has been cited by other articles:

				A. Mulch and C. P. Chamberlain Stable Isotope Paleoaltimetry in Orogenic Belts The Silicate Record in Surface and Crustal Geological Archives Reviews in Mineralogy and Geochemistry, October 1, 2007; 66(1): 89 - 118. [Abstract] [Full Text] [PDF]

				D. Proust, J. Caillaud, and C. Fontaine CLAY MINERALS IN EARLY AMPHIBOLE WEATHERING: TRI- TO DIOCTAHEDRAL SEQUENCE AS A FUNCTION OF CRYSTALLIZATION SITES IN THE AMPHIBOLE Clays and Clay Minerals, June 1, 2006; 54(3): 351 - 362. [Abstract] [Full Text] [PDF]