Graphical representation of particle shape using triangular diagrams: an Excel spreadsheet method

Abstract

Analysis of the shape of sedimentary particles can provide information about their transport history and aid facies differentiation and the characterization of depositional environments. Triangular (Sneed and Folk) diagrams, employing ratios of the three orthogonal particle axes, have been advocated as the most appropriate method for unbiased presentation of primary particle shape data. A spreadsheet method for the production of these diagrams is described. Clast data-sets from a range of environments are presented using this method. An alternative use of the spreadsheet for the presentation of sedimentary fabric shape is suggested.

DNA tests probe the genomic ancestry of Brazilians

“…We can observe from the figure that most of the white individuals of all the regions examined clustered in the "European" vertex of the triangle plot ( Figure 3A-E), although a proportion of them were scattered throughout the triangle area. As can be checked in Table 1, all average European contributions to white individuals were above 0.700, with a maximum of 0.819 in Southern Brazil (a region of heavy European immigration) and a minimum of 0.709 in Minas (28). We used our set of 40 insertion-deletion polymorphisms (22) and the Structure program to study 272 Brazilians self-defined as White (11,18).…”

Dimensional specific physical properties of fan palm fruits, seeds and seed coats (Washingtonia robusta)

“…This method of representing particle shape employs a triangular diagram in which ratios of the three orthogonal axes of the particle are plotted. Particles are envisaged as lying in the continuum between blocks (or spheres), slabs (discs, oblate) and rods (prolate) which mark the corners of the plotted diagram (Graham and Midgley, 2000). The geometric mean diameter, sphericity, aspect ratio, bulk density, true density and porosity values of the samples were calculated according to Mohsenin (1986).…”

Abrasion of flat rotating shapes

“…The approach taken in Refs. [2][3][4][5][6][7][8][9][10][11] was to fit radius versus angle to a cubic polynomial, averaging over a range of acceptable fitting windows. Here we develop an alternative approach in which the pebble is photographed at multiple orientations with respect to the grid of pixels in the digital camera.…”

“…In geology, shapes are often described verbally (angular, rounded, elongated, platy) or by comparison to a standardized charts [1]. It is also common practice to construct dimensionless ratios from measured values of long versus intermediate versus short axes [6][7][8][9][10]. To better connect with the microscopic action of erosion, other shape quantifiers have been constructed in terms of the curvature [2] or the turning angle [5] at each point along the contour.…”