Natural variations in calcite dissolution rates in streams: Controls, implications, and open questions

• Published in: Geophysical research letters 2015-04, Vol.42 (8), p.2836-2843
• Main Authors: Covington, M. D., Gulley, J. D., Gabrovšek, F.
• Format: Article
• Language: English
• Subjects: Bedrock; bedrock channel; Calcite; Calcite dissolution; Carbonates; catchment hydrology; Channels; chemical variability; Control equipment; Dilution; Dissolution; Dissolving; Erosion; Estimates; Evolution; Geological surveys; Karst; magnitude and frequency; Mathematical models; Rivers; Rock; Rocks; Silicates; Strata; Streams; Surveying; Variability
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063044

Models of bedrock channel evolution typically assume that chemical erosion is negligible in comparison to mechanical erosion. While this assumption is reasonable for channels in silicate rocks, it is questionable within highly soluble strata such as carbonates. The magnitude and variability of calcite dissolution rates in streams has remained as a critical unknown for models of bedrock incision and karst conduit formation. Here we use U.S. Geological Survey data to estimate calcite dissolution rates from 77 different streams located in a wide range of settings. The calculated rates are commonly on the order of ∼1 mmyr−1, which is 1 to 2 orders of magnitude larger than previous estimates. We also find that PCO2 is the strongest control on at‐a‐site variability, though some sites also display dilution‐controlled variability. Typically, dissolution rates vary within a relatively narrow range, which has important implications for the relative importance of chemical and mechanical erosion. Key Points Calcite dissolution rates in streams are frequently on the order of 1 mm/yr PCO2 is the primary control on at‐a‐site dissolution rate variability Framework for relative importance of chemical and mechanical stream incision