Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-05T04:14:55.870Z Has data issue: false hasContentIssue false
  • English
  • Français

Development of unusual rock weathering features in the Cordillera Blanca, Peru

Published online by Cambridge University Press:  20 January 2017

Donald T. Rodbell ,
Holli M. Frey ,
Matthew R.F. Manon ,
Jacqueline A. Smith  and
Nicholas A. McTurk
Donald T. Rodbell*
Affiliation:
Geology Department, Union College, Schenectady, NY 12308, USA
Holli M. Frey
Affiliation:
Geology Department, Union College, Schenectady, NY 12308, USA
Matthew R.F. Manon
Affiliation:
Geology Department, Union College, Schenectady, NY 12308, USA
Jacqueline A. Smith
Affiliation:
Department of Physical & Biological Sciences, The College of Saint Rose, Albany, NY 12203, USA
Nicholas A. McTurk
Affiliation:
Geology Department, Union College, Schenectady, NY 12308, USA
*
*Corresponding author. Fax: + 1 518 388 6417. E-mail address:rodbelld@union.edu (D.T. Rodbell).
Get access Rights & Permissions [Opens in a new window]

Abstract

Mylonite textures in granodiorite boulders are responsible for higher rates of surface denudation of host rocks and the progressive development of unusual rock weathering features, termed weathering posts. These textures are characterized by smaller grain sizes, higher biotite content, and a higher biotite axial ratio in host rocks relative to weathering posts. Elemental concentrations do not show a significant difference between weathering posts and the host rocks in which they are found, and this reflects the absence of a weathering residue on the rock surfaces. Chemical weathering loosens the bonds between mineral grains through the expansion of biotite, and the loosened grains fall off or are blown off the boulder surface and continue their chemical alteration in the surrounding soil. The height of weathering posts on late Quaternary moraines increases at a linear rate of ~ 1.45±0.45 cm (1000 yr)– 1 until post heights reach the diameter of host rocks. Such a rate of boulder denudation, if unrecognized, would generate significant errors (> 20%) in cosmogenic exposure ages for Pleistocene moraines. Given the paucity of boulders with diameters that significantly exceed 1.5 m, the maximum age of utility of weathering posts as a numeric age indicator is ~ 100 ka.

Keywords

Rock weatheringMoraine datingExposure agesTropical glaciation
Type
Original Articles
Information
Quaternary Research , Volume 77 , Issue 1 , January 2012 , pp. 149 - 158
Copyright
University of Washington

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Atherton, M.P., Sanderson, L.M., (1987). The Cordillera Blanca Batholith: a study of granite intrusion and the relation of crustal thickening to peraluminosity. Geologische Rundschau 76, 213–232.Google Scholar
Balco, G., Stone, J.O.H., Lifton, N.A., Dunai, T.J., (2008). A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10 Be and 26Al measurements. Quaternary Geochronology 3, 174–195.Google Scholar
Birkeland, P.W., (1973). Use of relative age-dating methods in a stratigraphic study of rock glacier deposits, Mt. Sopris, Colorado. Arctic and Alpine Research 5, 401–416.CrossRefGoogle Scholar
Birkeland, P.W., (1974). Pedology, Weathering, and Geomorphological Research. Oxford University Press, New York.Google Scholar
Birkeland, P.W., (1999). Soils and Geomorphology. Oxford University Press, New York.Google Scholar
Birkeland, P.W., Colman, S.W., Burke, R.M., Shroba, R.R., Meierding, T.C., (1979). Nomenclature of alpine glacial deposits, or what's in a name?. Geology 7, 532–536.Google Scholar
Blackwelder, E., (1931). Pleistocene glaciation in the Sierra Nevada and Basin Ranges. Geological Society of America Bulletin 42, 865–922.Google Scholar
Bland, W., Rolls, D., (1998). Weathering: Introduction to the Scientific Principles. Oxford University Press, New York.Google Scholar
Burbank, D.W., Cheng, K.J., (1991). Relative dating of Quaternary moraines, Rongbuk Valley, Mount Everest, Tibet: implications for an ice sheet on the Tibetan Plateau. Quaternary Research 36, 1–18.Google Scholar
Burke, R.M., Birkeland, P.W., (1979). Reevaluation of multiparameter relative dating techniques and their application to the glacial sequence along the eastern escarpment of the Sierra Nevada, California. Quaternary Research 11, 21–51.CrossRefGoogle Scholar
Chinn, T.J.H., (1981). Use of rock weathering-rind thickness for Holocene absolute age-dating in New Zealand. Arctic and Alpine Research 13, 33–45.Google Scholar
Clapperton, C.M., (1981). Quaternary glaciations in the Cordillera Blanca, Peru and the Cordillera Real, Bolivia. Memoria del Primer Seminario Sobre el Cuaternario de Colómbia. Revista Centro Interamericano de Fotointerpretacíon C.I.A.F, Bogotá. 93–111.Google Scholar
Colman, S.M., (1981). Rock-weathering rates as functions of time. Quaternary Research 15, 250–264.CrossRefGoogle Scholar
Colman, S.M., Pierce, K.L., (1980). Weathering rinds on andesitic and basaltic stones as a Quaternary age indicator, western United States. U.S. Geological Survey Professional Paper 1210.Google Scholar
Eggler, D.H., Larson, E.E., Bradley, W.C., (1969). Granites, grusses, and the Sherman erosion surface, southern Laramie Range, Colorado-Wyoming. American Journal of Science 267, 510–522.Google Scholar
Farber, D.L., Hancock, G.S., Finkel, R.C., Rodbell, D.T., (2005). The age and extent of tropical alpine glaciation in the Cordillera Blanca, Peru. Journal of Quaternary Science 759–776.Google Scholar
Gapais, D., (1989). Shear structures within deformed granites: mechanical and thermal indicators. Geology 17, 1144–1147.2.3.CO;2>CrossRefGoogle Scholar
Gosse, J.C., Phillips, F.M., (2001). Terrestrial in situ cosmogenic nuclides: theory and application. Quaternary Science Reviews 20, 1475–1560.Google Scholar
Isherwood, D., Street, A., (1976). Biotite-induced grussification of the Boulder Creek granodiorite, Boulder County, Colorado. Geological Society of America Bulletin 87, 366–370.Google Scholar
Petford, N., Atherton, M., (1992). Granitoid emplacement and deformation along a major crustal lineament: the Cordillera Blanca, Peru. Tectonophysics 205, 171–185.Google Scholar
Pierce, K.L., Obradovich, J.D., Friedman, I., (1976). Obsidian hydration dating and correlation of Bull Lake and Pinedale glaciations near West Yellowstone, Montana. Geological Society of America Bulletin 87, 703–710.Google Scholar
Rodbell, D. T. (1991). Late Quaternary glaciation and climatic change in the northern Peruvian Andes. Unpublished PhD. thesis, University of Colorado.Google Scholar
Rodbell, D.T., (1992). Lichenometric and radiocarbon dating of Holocene glaciation, Cordillera Blanca Perú. The Holocene 2, 19–29.CrossRefGoogle Scholar
Rodbell, D.T., (1993). Subdivision of late Pleistocene moraines in the Cordillera Blanca, Peru, based on rock-weathering features, soils, and radiocarbon dates. Quaternary Research 39, 133–143.Google Scholar
Schwartz, D.P., (1988). Paleoseismicity and neotectonics of the Cordillera Blanca Fault Zone, northern Peruvian Andes. Journal of Geophysical Research 93, 4712–4730.Google Scholar
Segall, P., Simpson, C., (1986). Nucleation on ductile shear zones on dilatant fractures. Geology 14, 56–59.Google Scholar
Servicio Nacional de Geología y Minería, . (1970). Mapa geológico del Departamento de Ancash (1:250,000). Ministerio de Energía y Minas, Lima.Google Scholar
Smith, D. N. (1988). Flora and vegetation of the Huascarán National Park, Ancash, Peru with preliminary taxonomic studies for a manual of the flora. Unpublished Ph.D. thesis, Iowa State University.Google Scholar
Smith, J.A., Rodbell, D.T., (2010). Cross-cutting moraines reveal evidence for North Atlantic influence on glaciers in the tropical Andes. Journal of Quaternary Science 25, 243–248.Google Scholar
Vernon, R.H., Williams, V.A., D'arcy, W.F., (1983). Grain-size reduction and foliation development in a deformed granitoid batholith. Tectonophysics 93, 123–145.Google Scholar
White, A.F., (2002). Determining mineral weathering rates based on solid and solute weathering gradients and velocities: application to biotite weathering in saprolites. Chemical Geology 190, 69–89.Google Scholar
White, A.F., Bullen, T.D., Schulz, M.S., Blum, A.E., Huntington, T.G., Peters, N.E., (2001). Differential rates of feldspar weathering in granitic regoliths. Geochimica et Cosmochimica Acta 65, 847–869.Google Scholar
Whitehouse, I.E., McSaveney, M.J., Knuepfer, P.L.K., Chinn, T.J., (1986). Growth of weathering rinds on torlesse sandstone, Southern Alps, New Zealand. Colman, S.M., Dethier, D.P., Rates of Chemical Weathering of Rocks and Minerals. Academic Press, San Diego. 419–435.Google Scholar
Wilson, J., Reyes, L., Garayar, J., (1967). Geología de los cuadrangulos de Mollebamba, Tayabamba, Huaylas, Pomabamba, Carhuaz, y Huari. Servicio de Geología y Minería Boletín 16, .Google Scholar