An Evaluation of Procedures Used in Computing Chemical Denudation Rates

Abstract

Research Article| January 01, 1971 An Evaluation of Procedures Used in Computing Chemical Denudation Rates RICHARD J JANDA RICHARD J JANDA U. S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information RICHARD J JANDA U. S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025 Publisher: Geological Society of America Received: 04 Feb 1970 Revision Received: 10 Aug 1970 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1971, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1971) 82 (1): 67–80. https://doi.org/10.1130/0016-7606(1971)82[67:AEOPUI]2.0.CO;2 Article history Received: 04 Feb 1970 Revision Received: 10 Aug 1970 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation RICHARD J JANDA; An Evaluation of Procedures Used in Computing Chemical Denudation Rates. GSA Bulletin 1971;; 82 (1): 67–80. doi: https://doi.org/10.1130/0016-7606(1971)82[67:AEOPUI]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Computations of chemical denudation rates (that is, the average rate of lowering of the earth's crust by chemical processes) should be based only upon those components of dissolved loads of streams that are derived from chemical weathering of rocks and soils, even though identification of those components is difficult and imprecise. Past computations of chemical denudation rates exaggerated by 1.4 to 2.4 times the significance of this process because they were calculated from total dissolved loads.Identification of separate denudation and nondenudation components in a water analysis can be done most readily for streams in crystalline silicate rock terrane where commonly 25 to 55 percent of the dissolved solids are HCO3−1, SO4−2, Cl−1, and NO3−1 that cannot be derived from the underlying rock; instead these ions are derived either directly from the atmosphere or from atmosphere-biosphere interactions. Most of the remaining solutes are derived from chemical weathering or rainfall, or both. Existing data are often insufficient to separate these two components, but atmospheric contributions to dissolved loads of dilute natural waters are substantial.The commonly observed increased concentration of dissolved solids in chemically polluted rivers is produced by concentration of natural dissolved loads by evaporation, and by addition of solutes not present in natural waters. Concentration of natural solutes represents a modification of natural denudation processes that does not change the rate of denudation. Addition of new solutes represents man-induced, accelerated chemical denudation.Extrapolation of modern chemical denudation rates to geologic situations is extremely imprecise because of uncertainties in assessing man's influence on present dissolved loads, in reconstructing the number and magnitude of past climatic changes, and in evaluating the effects of evolving flora and fauna. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.