Likewise, in Folk’s scheme the lithic end member is subdivided into volcanic, metamorphic and sedimentary varieties. Folk has taken this a step further where a distinction is made between potassium feldspars and plagioclases. In Dott’s scheme the different varieties of quartz and feldspar are lumped into their respective end members. Note that the percentage matrix is relative to the percentage of framework. In this scheme, sand-dominated rocks and sediments carrying less than 15% matrix are called arenites those with 15-75% matrix are wackes, and >75% matrix, mudstones. Folk’s 1966 classification of terrigenous sandstones (from Folk, 1968, Petrology of Sedimentary Rocks). 625-632) and later modified by Pettijohn, Potter and Siever, ( 1973 Sand and Sandstone, Springer-Verlag). Today, the popular classification schemes incorporate these three components in triangular QFL ĺplots like the one shown below, originally constructed by R.H.Dott, ( 1964, Journal of Sedimentary Petrology, v. Thus, there is a convincing argument that clast composition should be incorporated into classification schemes.ĭiligent petrographic analysis and point-counting of terrigenous sands and sandstones (over the same historical period) demonstrated that the dominant framework grain types are quartz, feldspar and lithic fragments (QFL). This, in turn tells us something about tectonics, for example the contrasting composition of sediment derived from mountain belts versus stable cratons (note that the unifying theory of plate tectonics was still 2 to 3 decades away). It has long been recognised that the mineralogical composition of sandstone contributes a great deal of knowledge about the sources from which the sediment was derived, the potential changes in composition during sediment transport, and depositional histories. those lacking significant matrix) and wackes – those rocks containing significant matrix.
#Folk ternary diagram plus#
However, textural properties such as the percentage of matrix (clay plus silt) did provide grounds for distinguishing between ‘clean’ sandstones (i.e. Qualifications such as pebbly, silty or muddy might be applied, but this said nothing about the variability of mineral types. A classification based on texture alone was deemed inadequate if the rock or sediment had >50% sand, then it was a sandstone, or arenite. One of the central topics of discussion was the relative importance of sandstone texture versus sandstone composition. Several schemes were proposed and debated few were accepted. William, F Turner, C Gilbert, Robert Dott, and R. The classification of sandstones matured in the 1940s through 1960s many publications were devoted to the subject some of the key players were Robert Folk, Harvey Blatt, Francis Pettijohn, Raymond Siever, P. If I wish to talk about a particular rock or fossil, then the people who are interested in such things will have a frame of reference to understand and contribute to the discussion, based on whatever classification scheme applies. Classification schemes don’t just name things, they organize them according to their properties, appearance, structure, composition. In science, classification of things is one of those tasks we readily identify as a crucial component of knowledge but prefer that someone else does it.
#Folk ternary diagram how to#
Legend.bubbles ("right", z=rys$Sorting, nleg=4, pch=21, col="black",Ĭex=1, z.cex.range=c(0.5,3), x.intersp=1.2, y.intersp=1.This post is part of the How To…series – how to classify sandstones using QFL plots Percent <- class.percent(sed.phi, mode="total") #Calculating the percentage of weight in each textural class #Pejrup diagram with Sorting as bubbles for different environments Rysgran.ternary (x, method="shepard", show.labels = TRUE) X<-percent #choosing only the 'sand', 'silt' and 'clay' columns Percent <- class.percent(camargo2001, mode="total") See Also gran.stats, class.percent, rysgran.ternary, rysgran.hist, legend.bubbles Examples Journal Sedimentary Petrology, 24:151-158. (1954) Nomenclature based on sand-silt-clay ratios. in: Tide-influenced sedimentary environments and facies. (1988) The triangular diagram used for classification of estuarine sediments: a new approach. (2000) A revised textural classification of gravel-free muddy sediments on the basis of ternary diagrams. Further graphical parameters Value Details When z argument is used to draw bubble plots the legend.bubbles function should be used to draw the legend accordingly References