Grain Size and Sorting

Although now over 25 years old, R. L. Folk's The Petrology of Sedimentary Rocks (1974) is still an extremely valuable reference for anyone seeking to do basic, descriptions of sediments. The following pages/sections will be especially useful during this course:

Grain size scale
Sampling, (starting on page 15)
Preparation of samples for analysis (starting on page 16)
Seperation of sand from mud (beginning on page 19)
Size analysis by sieving (starting on page 31
Statistical parameters of grain size, which includes discussions of both graphical methods and the "method of moments" (beginning on page 45)

Most students find Folk's discussions of these subjects a good supplement to our text -- especially during grain size analysis for the Tar River project. With a few obvious exceptions (that will be clear from our text and from the lectures) Folk's treatment of sediment grain size is as valid today as it was 2.5 decades ago.

The following videos (which run on RealPlayer or compatible video player) are from the USGS. They offer good, succinct, instructions on the 3 methods we will use in our laboratory analysis of the Tar River samples.

· Wet sieving video (or, watch it from the link on the USGS grain size site)

· Pipetting video (or, watch it from the link on the USGS grain size site)

· Dry Sieving video (or, watch it from the link on the USGS grain size site)

I urge you to watch these videos BEFORE we go into the field!

The following descriptions of procedures and data sheets will be useful in our laboratory analysis of sediments from the Tar River:

· Pipette Analysis

· Pipette Analysis Data Sheet – USE THIS FOR YOUR PIPETTE DATA!

· Dry Sieving

· Dry Sieve Analysis Data Sheet – USE THIS FOR YOUR SIEVE DATA!

Need help with Excel (available in the departmental student computer lab) or with grain-size statistics? Try these:

· Basic Excel tutorials from USD and FGCU.

· A detailed discussion about bar graphs and histograms – including step-by-step instructions for creating a histogram. (Remember, you will be creating histograms for your grain-size exercise!)

· Another explanation of Excel histograms.

· Finally, the following YouTube videos may be helpful: Creating a Histogram in Excel 2010, Installing the data analysis tool pack, Excel in Depth – Frequency Distribution: #1258, How to Create a Chart in Excel 2010, and numerous other such videos (just search!).

· A summary explanation of the calculation of grain-size statistics (graphical methods and the methods of moments).

Other interesting/useful resources:

An on-line lecture on occurrence, mineralogy, textures, and structures of sedimentary rocks by Stephen Nelson, Tulane) summarizes much of the topic.
A few useful tools to help you describe sediments and sedimentary rock textures in lab and in the field:

a decent grain size chart (yes, it includes phi sizes, sieve sizes, and mm sizes!),
a grain size chart that may be useful in the field,
a sorting comparator chart, and
a simplified, all-in-one grain-size/rounding/sorting chart.

A couple of classification diagrams for clastic sedimentary rocks:

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