GGR201H5F

Fall 2025

Practical Exercise 3: Sediment Analysis (Part ii)

Due: Tuesday 2nd  Dec, 9 pm

Outline & rubric

Introduction:

In this practical you are investigating the sedimentary properties of seven sediment samples (Samples A-G) collected from contrasting depositional environments in the region; using the data compiled from a series of sediment descriptions and analyses you will attempt to match each sample to the location at which it was collected - Sample sites 1-7. The sample letters and site numbers have been randomised - accordingly, this exercise requires an appreciation of how sedimentary characteristics may reflect the geomorphological origin, transport history and depositional environment of contrasting landform. and environmental settings (although a simple visual assessment will provide plenty of clues!).

The techniques used in this analysis are widely used in geomorphological studies:

1.   Sediment description (a qualitative description of average grain size characteristics)

2.   Clast roundness analysis (using the Powers roundness classification)

3.   Grain size (sieve) analysis

These techniques are outlined in the sections below, together with an outline of the required report structure and rubric.

Sample site locations and details

The seven sample sites are illustrated in the pdf file

GGR201H5F_2025_Practical_3_Sediment_Sample_Sites and are listed below:

•   Woodbine Beach, Toronto: Sites 3 and 6

•   Sonnet Beach, Oakville: Sites 1 and 4

•   Sixteen-Mile Creek, Oakville (Glenorchy Conservation Area): Sites 2 (channel bed) and 5 (bar top)

•   Twelve-Mile Creek (un-named tributary), Pelham: Site 7 (channel bed – dry at time of sampling)

Analysis 1: Sediment description

This exercise entailed a simple description of the general grain size characteristics of each sample. For fine sediment samples this can be obtained using the fine sediment description flowchart (e.g. fine sand, silt, etc) and the Grain Size cards.

Analysis 2: Powers Roundness Analysis

Powers roundness analysis was conducted on a minimum of 25 randomly-selected individual clasts; reduced counts for Sample D reflects the fewer number of large clasts in this sample. Raw counts and percentage data are presented in the following Excel file:

GGR201H5F_2025_Practical_3_Powers_roundness_data.xls

Note the following abbreviations:

•   va = very angular

•   a = angular

•   sa = sub-angular

•   sr = sub-rounded

•    r = rounded

•   wr = well-rounded

Analysis 3: Grain Size Analysis

Grain size analysis was conducted for each sample outside of practical classes using a two-stage sieving methodology as follows:

1.   Dried and weighed sub-samples were passed through a 64mm to 2mm sieve stack (-6 to -1 phi). This included a 30-minute period mounted in an automatic sieve-shaker.

2.   The sediment retained on each sieve was weighed and recorded; sediments finer than 2mm (the <2mm fraction) were retained in the collecting tray at the base of the stack and weighed in advance of the second (fine-grained) sieving phase.

3.   The <2mm fraction was emptied into a 1mm to 63μm sieve stack and mounted in a sieve

shaker for 30 minutes. The sediment retained on each sieve and the fraction finer than 63μm (collected in the base tray) was weighed and recorded.

4.   Results were compiled in Excel as tables logging the sediment weight for each size fraction and converted to percentage data. The data is available in the following Excel file:

GGR201H5F_2025_Practical_3_Grain_Size_Analysis.xls

Note that data for each Sample is presented on a separate tab and includes examples of simple histogram and line graphs for each sample. The spreadsheet also includes an example of the worked data (see instructions below).

Report structure and guidance:

1. Introduction (5 marks; max 100 words)

Write a short introduction to the report outlining the broad aims of the practical and the context of the seven sample sites (this can be summarised from the briefing above – no citations needed).

2. Methods (10 marks; max 200 words)

Write a short methods statement covering the sediment description (including color), grain-size and Powers Roundness analysis. You may use the text above as the basis for this and can copy- and-paste the grain-size analysis description (no citation needed).

3. Results (35 marks; max 400 words)

3.1: Sediment description

•    Produce a table (Table 1) that presents a qualitative description (as recorded across the first two weeks of the lab classes for Practical 3) for Samples A-G.

3.2: Powers roundness analysis

•    Using the aggregated Powers roundness data file present (i) a data table (Table 2) and (ii) a

histogram (or histograms) showing Powers roundness classes for each of the sediment samples (label this as Figure 1). Compare and contrast the roundness characteristics of the sediment samples. Note that only a limited number of clasts are available for Sample D.

3.3: Grain-size analysis

GGR201H5F_2025_Practical_3_Grain_Size_Analysis.xls presents a complete grain size analysis data set for Samples A-G. Use this data for the analysis as follows:

•   Calculate the cumulative % coarser for each phi class as an additional column in each sample’s worksheet (see the worked example in the results spreadsheet)

•    For each sample produce a combined histogram / x-y chart showing (i) the grain size

distribution (%) as a barchart using the primary Y axis and (ii) the cumulative % coarser as an x- y chart using the secondary Y axis (see the worked example in the results spreadsheet). Note  you can modify the style, colour, etc of these graphs if you wish. Present these graphs as Figures 2-8.

•    Present an X-Y chart (Figure 9) that combines the cumulative % coarser curves for all 7 samples

– see Trenhaile’s (2016) Figure 2.10 (below) for examples of appropriate chart styles

(Trenhaile’s data comes from an earlier paper published in 1978 – this is also available in Files / Resources). Ensure you provide a key to the samples and label the axes.

•   Compare and contrast the grain size analysis data with reference to your figures – ensure you consider the overall grain size and sorting characteristics.

4. Discussion and conclusions (50 marks; max 500 words)

Complete the table below to match – in your judgement – each sediment sample (A-G) to one of the sample sites (1-7) and include it in your report as Table 3:

Table 3: Sediment sample / site matching:

Write a discussion of the data that explains your interpretation and matching of samples to sites, ensuring you consider how the sedimentary characteristics of the samples relate to the depositional environment and likely geomorphological processes at each site. Support your interpretation of the data with reference to one or more of the following sections of Trenhaile (2016), or any other academic texts or papers:

•   Chapter 2, p.42-46

•   Chapter 10, p.343-344

•   Chapter 12, p.400-404

•   Chapter 13, p.429-430; 438-439;

Use the conclusions section to briefly identify any other additional landform or sedimentary data that would have helped you make your interpretations.

Due date: Tuesday 2nd  December, 9 pm

Submission: Online submission as a .pdf file via Quercus / Practical Exercise 3. Use the following

filename: SURNAME_Student-number_Practical_3.pdf

References and other useful literature

•   Trenhaile (2016) Chapter 2: Sediments (p.42-46)

•   Goudie, A (1990) Geomorphological Techniques (2nd Ed). Routledge. p.127-130. (See Quercus / Files / Resources)

Trenhaile (2016) Fig. 2.10: