Petrology of Terrigneous Rocks – Geology 635 - Spring 2014
Outline of Course
During the semester I will give a series of lectures related to the controls that weathering plays on the
developed of terrigenous rocks. In addition, I will ask each of you to present and lead a discussion on
various papers that you will be assigned to read. Required readings will be provided as pdf files that you
can access through Blackboard.
Class participation is required. If you do not participate, then you will lose points from your final
average grade.
In addition, we will collect a set of samples from a section of regolith exposed near the old house
located at the NE corner of the Santa Margarita Ecological Reserve. We will then chemically analyze the
samples, and produce thin sections for microscopic study. I will then show you how to use a variety of
C# programs that I have written to (1) assess whether or not weathering at the study site can be
explained by a compositional linear trend, (2) identify in a rigorous statistical sense what elements were
not affected by weathering and thus can be used as a reference frame for calculating elemental and bulk
mass changes, and (3) based on mass balance arguments quantify what elemental and bulk mass
changes have taken place within the weathering profile. After completion of the above work, you will
be required to complete a take home exam. The exam will test your ability to evaluate a complete set of
chemical data similar to those derived from the site at SMER. It will cover all aspects of the study
conducted during this class, including the knowledge obtained from reading and presenting the key
results of a series of pertinent papers, as well as the lab work and statistical work covered during
lectures. The exam will be provided to you on Monday, April 18 and is due in my office on Wednesday
April 23 by 4:00 pm.
The ultimate goal of this class is to utilize the data obtained during field and laboratory work to write a
paper outlining the effects of clay translocation on linear compositional trends. Those of you who wish
to be coauthors on this paper, will be required to work with me during the summer to complete the
project and the writing of the paper.
The exam that you will take will be worth 90% of your final grade. The remaining 10% will be
based on class participation.
What are terrigenous rocks?
a. Location
b. Grain size
c. Composition
The Regolith – the ultimate source of most terrigneous rocks
a. Soils
b. Corestones, saprock, and saprolite
Nature of incongruent reactions within the regolith
a. Plagioclase weathering
b. Biotite weathering
Recognizing polygenetic regolith
a. Effects of translocation
b. Clay minerals and how to identify them
Calculating chemical and physical parameters associated with weathering
a. Calculating bulk and elemental mass changes
b. Measuring bulk and grain densities and calculating porosities
c. Calculating volumetric strains
Exam and Field Trip Schedule
Field Trips: during class we will set a number of dates for completing the field work discussed
Below is a list of papers that we will try and read during this class. You can also
find them in pdf form on Blackboard.
Ague, J. J., 1994. Mass transfer during Barrovian metamorphism of pelites, south-central Connecticut. I:
Evidence for changes in composition and volume. Am. J. Sci. 294, 989-1057.
Aitchison, J., 1986. The Statistical Analysis of Compositional Data. Chapman and Hall, London, 416 pp.
Aitchison, J., 1989. Measures of location of compositional data sets. Math. Geol. 21, 787-790.
Girty G.H., Biggs, M.A., and Berry, R.W., 2008. An unusual occurrence of probable Pleistocene corestone
within a Cretaceous dioritic enclave, Peninsular Ranges, California. Catena 74, 43-57.
Girty, G.H., Colby, T.A., Rayburn, J.Z., Parizek, J.R., Voyles, E.M., 2013. Biotite-controlled linear
compositional trends in quartz dioritic to tonalitic saprock, Santa Margarita Ecological Reserve,
southern California, USA. Catena 105, 40-51.
Girty, G.H., Gebhart, K.L., Replogle, C.T., Morton, N., Purcell, J.W., Parizek, J.R., Carrasco, T., Errthum, R.,
Groover, K., 2014. Reconstructing the regolith from erosionally exhumed corestone and saprock
derived from the Cretaceous Val Verde tonalite, Peninsular Ranges, southern California, USA: A case
study. Catena 113, 150-164.
Graham, R.C., Rossi, A.M., and Hubbert, K.R., 2010. Rock to regolith conversion: Producing hospitable
substrates for terrestrial ecosystems. GSA Today 20, 4-9.
Knecht, A., 1971. Soil survey of western Riverside Area, California. U.S. Gov. Print. Office, Washington
D.C. 157 pp.
Kretz, R., 1985. Calculation and illustration of uncertainty in geochemical analyses. J. Geo. Education 33,
Mateu-Figueras, G., Pawlowsky-Glahn, V., and Egozcue, J.J, 2011. The principles of working on
coordinates. In: Pawlowsky-Glahn, V., and Buccianti A., 2011. (Eds.), Compositional data analysis.
John Wiley & Sons, Ltd, pp. 31-42.
McLennan, S., 1993. Weathering and global denudation. J. Geol. 101, 295–303.
Moore, D.M., and Reynolds, R.C., Jr., 1997. X-ray Diffraction and the identification and analysis of clay
minerals. Oxford Univer. Press, NY, 378 pp.
Nesbitt, H.W., 1979, Mobility and fractionation of rare earth elements during weathering fo a
granodiorite. Nature 279, 206-210.
Nesbitt, H.W., Markovics, G., 1997. Weathering of granodioritic crust, long-term storage of elements in
weathering profiles, and petrogenesis of siliciclastic sediments. Geochim. Cosmochim. Acta 61,
Nesbitt, H.W., Young, G.M., 1982. Early Proterozoic climates and plate motions inferred from major
element chemistry of lutites. Nature 299, 715-717.
Nesbitt, H.W., Young, G.M., 1984. Prediction of some weathering trends of plutonic and volcanic rocks
based on thermodynamic and kinetic considerations. Geochim. Cosmochim. Acta 299, 1523–1534.
Nesbitt, H.W., Young, G.M., 1989. Formation and diagenesis of weathering profiles. J. Geol. 97, 128–
Nesbitt, H.W., Fedo, C.M., and Young, G.M., 1997. Quartz and feldspar stability, steady and non-steadystate weathering, and petrogenesis of siliciclastic sands and muds. J. Geo. 105, 173-191.
Nesbitt, H.W., Markovics, G., and Price, R.C., 1980. Chemical processes affecting alkalis and alkaline
earths during continental weathering. Geochim. Cosmochim. Acta 44, 1659-1666.
Nesbitt, H.W., Young, G.M., McLennan, S.M., and Keays, R.R., 1996. Effects of chemical weathering and
sorting on the petrogenesis of siliciclastic sediments, with implications for provenance studies. J. Ge.
104, p. 525-542.
Nesbitt H. W., Markovics G., and Price R. C. (1980) Chemical processes
Nettleton, W.D., Flach, F.W., and Nelson, R.E., 1970. Pedogenic weathering of tonalite in southern
California. Geoderma 4, 387-402.
Pawlowsky-Glahn, V., and Egozcue, J.J., 2006. Compositional data and their analysis: an introduction. In:
Buccianti, A., Mateu-Figureeras, G., and Pawlowsky-Glahn, V. (Eds.), Compositional Data Analysis in
the Geosciences: from Theory to Practice. Geol. Soc. London, Spec. Pub. 264, pp. 1-10.
Pawlowsky-Glahn, V., and Buccianti A., 2011. (Eds.), Compositional data analysis. John Wiley & Sons, Ltd,
Pearl, F.B., Waters, M.R., 1999. A geoarchaeological assessment of alluvial valleys at Camp Pendleton
with an overview of the important natural site formation process. Pac. Coast Archeol. Soc. Quart. 35,
Rood, D.H., Anooshelpoor, R., Balco, G., Brune, J., Brune, R., Ludwig, L.G., Kendrick, K., Purvance, M., and
Saleeby, I., 2012. Testing seismic hazard models with Be-10 exposure ages for precariously balanced
rocks. Geophy. Res. Abs. 14, EGU2012-9152.
Schedl, A., 1998. Log ratio methods for establishing a reference frame for chemical change. J. Geol. 106,
Tan, S.S., and Kennedy, M.P., 2000. Digital geologic map of the Temecula 7.5′ quadrangle, San Diego and
Riverside counties, California. Calif. Depart. of Conserv. Div. Mines and Geol.
Tolosana-Delgado, R., Otero, N., and Pawlowsky-Glahn, V., 2005. Some basic concepts of compositional
geometry. Math. Geol. 37, 673-680.
Velde, B., 1995. Origin and Mineralogy of Clays. Springer, NY, 334 pp.
von Eynatten, H., 2004. Statistical modeling of compositional trends in sediments. Sediment. Geol. 171,
von Eynatten, H., Barcelo-Vidal, C., and Pawlowsky-Glahn, V, 2003. Modelling compositional change: the
example of chemical weathering of granitoid rocks. Math. Geol. 35, 231-251.
von Eynatten, H., Pawlowsky-Glahn, V., and Egozcue, J.J., 2002. Understanding perturbation on the
simplex: A simple method to better visualize and interpret compositional data in ternary diagrams.
Math. Geol. 34, 249-257.
Warren, N.H., and Girty G.H., 1999. A Matlab 5 program for calculating the statistics of mass change. J.
Geosci. Edu. 47, 313-320.
Woronow, A., and Love, K. M., 1990. Quantifying and testing differences among means of compositional
data suites: Math. Geo. 22, 837-852.

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