Ledge Point Sand

Ledge Point is a naturally sorted coastal bioclastic sand from a shallow water high energy environment (Beemer et al. 2018, 2019, 2020, 2022). The coastal sand was collected from the Ledge Point beach-dune complex near Perth, Western Australia. Ledge Point consists of neritic remnants of marine shell and terrigenous material highly reworked by waves and wind, with calcium carbonate contents above 89%. The sand is classified as having irregular particle shape, as shown in Fig. 4.175. Selected DIA images of Ledge Point are also presented in Fig. 4.176, which help confirm the classification.

Grain size distributions of Ledge Point sand are presented using several size descriptors in Fig. 4.177. Fig. 4.178 also depicts variation between number and volume distribution. The size of the number distribution is dominated by the finer particles while volume distribution is dominated by the larger particles. The grain size D₅₀ of Ledge Point is 238 µm (Li et al. 2021). Typical particle size diameters in µm corresponding to several particle size descriptors are presented in Table 4.118. Comparison between EQPC sizes corresponding to various particle size diameters by weight/volume and number distributions are also presented in Table 4.119.

The density distribution for a number of commonly used shape descriptors is presented in Fig. 4.179 and summarized in Table 4.120. The distribution is clearly non gaussian and is thus fit with Johnson’s parameters. The fitting parameters are summarized in Table 4.121, and the goodness of fit is depicted in Fig. 4.180.

Fig. 4.175. Photo of Ledge Point sand with a 19 mm diameter US Penny for scale.

Fig. 4.176. Images of Ledge Point acquired using 2D DIA.

Table 4.118 Typical particle size diameters in µm corresponding to several particle size descriptors (by weight/volume distribution).

Ledge Point	D1	D5	D10	D30	D50	D60	D90	D99
Feret-max	55	85	112	230	322	371	693	1337
EQPC	39	62	80	172	238	274	494	907
Feret-min	37	58	74	147	205	235	419	792

Table 4.119 Typical EQPC corresponding to various particle size diameters by weight/volume and number distributions.

Ledge Point	D1	D5	D10	D30	D50	D60	D90	D99
Volume	39	62	80	172	238	274	494	907
Number	3	4	4	6	11	20	72	208

Table 4.120 Statistics of particle shape descriptors for Ledge Point by number and volume distributions.

Ledge Point	AR	S	Cx	Rwadell
Number
Mean	0.64	0.67	0.88	0.68
Median	0.65	0.69	0.89	0.68
Standard Deviation	0.14	0.11	0.05	0.13
Volume
Mean	0.63	0.66	0.89	0.65
Median	0.64	0.67	0.90	0.66
Standard Deviation	0.14	0.11	0.05	0.13

Table 4.121 Johnson fitting parameters for Ledge Point.

Ledge Point	γ	δ	ξ	λ
AR	-0.92	1.78	-0.08	1.19
S	-4.57	2.67	-1.13	2.14
Cx	-4.20	1.69	-0.01	0.99
Rwadell	-1.36	3.37	-0.45	1.84

Fig. 4.177. Particle size distributions using various size descriptors.

Fig. 4.178. Particle size volume and number distributions.

Fig. 4.179. Particle shape density distributions (based on volume) for Ledge Point.

Fig. 4.180. Johnson fitting of shape descriptors for Ledge Point.