Ocadsdcc
SEDIMENTOLOGY LABS
COURSE FALL 2019
SEDIMENTOLOGY
SEPTEMBER 2019
Members:
Ocaña Lisbeth
Salazar Dylan
Salazar Solange
Ocadsdcc
SEDIMENTOLOGY LABS
COURSE FALL 2019
LABORATORY 1:
TEXTURAL ANALYSIS, CLASIFICATION AND
INTERPRETATION OF SEDIMENTS
1) Complete the table by summing the weights of individual fractions, and converting the
weight of each fraction to a percentage and cumulative percentage (particles larger than a
certain value). 100% of the particles are larger than the smallest particle size.
Sieve Diameter Sample weight
(phi)
(g)
%
Cumulative %
(larger than)
log
-1,25
0,3
1,2
1,2
0,079181
-1
0,1
0,4
1,6
0,20412
-0,75
0,15
0,6
2,2
0,342423
-0,5
0,2
0,8
3
0,477121
-0,25
0,25
1
4
0,60206
0
0,3
1,2
5,2
0,716003
0,25
0,5
2
7,2
0,857332
0,5
0,8
3,2
10,4
1,017033
0,75
1,4
5,6
16
1,20412
1
2
8
24
1,380211
1,25
3,3
13,2
37,2
1,570543
1,5
4,3
17,2
54,4
1,735599
1,75
4,1
16,4
70,8
1,850033
2
3,3
13,2
84
1,924279
2,25
1,9
7,6
91,6
1,961895
2,5
1,1
4,4
96
1,982271
2,75
0,5
2
98
1,991226
3
0,2
0,8
98,8
1,994757
3,25
0,1
0,4
99,2
1,996512
3,5
0,1
0,4
99,6
1,998259
0,4
100
2
remainder
0,1
25
Ocadsdcc
SEDIMENTOLOGY LABS
COURSE FALL 2019
2) Plot a histogram of fraction percentage versus (frequency plot). The phi-scale stretches the
distribution for the finer scales.
3) Plot a graph of cumulative weight percentage versus .
4) Plot the cumulative weight percentage versus with a log-probability scale for the ordinate. A
normal distribution plots as a straight line.
% vs φ scale
18
16
14
12
10
8
6
4
2
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
-2
Sieve Diameter (phi)
%
Cumulative % vs φ scale
100
91,6
96
98 98,8 99,2 99,6 100
84
80
70,8
60
54,4
37,2
40
24
16
20
10,4
1,2 1,6
2,2
3
4
5,2 7,2
0 0,25 0,5 0,75
1
1,25 1,5 1,75
2
2,25 2,5 2,75
3
3,25 3,5
0
1 -1,25
2 3 4-1 5 -0,75
6 7 -0,5
8 9 -0,25
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
-20
Cumulative % (larger than)
Sieve Diameter (phi)
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SEDIMENTOLOGY LABS
COURSE FALL 2019
log
2,5
2
1,5
1
0,5
0
0
20
40
60
80
100
120
Ocadsdcc
SEDIMENTOLOGY LABS
COURSE FALL 2019
Using the cumulative frequency curve and the formula provided, estimate the graphic mean,
graphic standard deviation, graphic skewness, mode and median grain size for the distribution.
For example, 16 % of the cumulative weight of the sample consists of grains larger than 16;
84% of the sample consists of grains larger than . Graphic standard deviation is a measure of
sorting. Graphic skewness is a measure of the asymmetry of the distribution. (Negative
skewness indicates as excess of large particles, or winnowing of fines, positive skewness
indicates an excess of small particles, as in a muddy sand). The mode corresponds to the most
abundant fraction of the sample. The median grain size is?
6) The cumulative frequency plot has two straight-line segments of different slope. Why?
Graphic mean
Graphic
standard
deviation
1,3333333
0,3125
Sorting
Skewness
0,6912879
-0,46875
Median grain
size
1,25
Negative
skewness
indicates as
excess of large
particles
The cumulative frequency plot has two straight-line segments of different
slope. Why?
When an excess of fine particles is present in a sample,the frequency curve has a
fine-size “tail” and the grain-size distribution is said to be fine-skewed, or
positively skewed (fine sediment has positive phi values; Fig. 2.5A. When a coarse
tail is present, the grain population is coarse-skewed, or negatively skewed (Fig.
2.5B). (Boggs, 2009)
We have two samples, the samples go from coarse to fine.