Backstrip 1.2 Instructions
You can backstrip a section in three steps. First, make a data file using a text editor (like TextEdit.app) and save it as backstripData.txt. Next, launch Terminal.app, navigate to the the Backstrip app, and type ./Backstrip. The program will automatically open your data file, as long as the data file is in the same directory as the Backstrip program. The program will show you the results as it runs, which might take a while for large data sets. The program will automatically save your results in a file called backstripResults.txt. Finally, you can open your output file in any program like Excel to plot it.
When you download Backstrip 1.2, it should be in a folder called backstrip with a test data file. Skip ahead to the section below called Running the program to test that it works. If it does, make your own data file and backstrip your own data.
Making a data file
Use a text editor to make your data file. TextEdit.app comes free with the macOS, but TextWrangler (also free from Bare Bones Software) and BBEdit (from Barebones Software) are highly recommended. Save your file as backstripData.txt. If you use TextEdit, be sure to save it as .txt file and not as an .rtf file.
Enter your data starting with the uppermost layer and ending with the bottom layer. Your data set will run correctly only if it is in stratigraphic order (youngest at the top, oldest at the bottom). After the last set of data, be sure to press return, or it won't read the last line of data.
For each layer, type the following in order on one line:
- thickness (in meters, including a decimal point)
- a blank space
- water depth (in meters, including a decimal point)
- a blank space
- the lithologic code (no decimal point).
Your data should look something like this:
50.0 2.0 1
0.0 0.0 1
21.5 25.0 2
34.5 10.0 2
0.0 0.0 1
20.0 25.0 2
52.5 10.0 2
38.0 10.0 2
37.1 25.0 2
1.0 2.0 1
You should note several things. The youngest layer is at the top; the oldest layer is at the bottom. In the actual data file, I would make sure to press return after the last (oldest) layer. The youngest layer is 50.0 meters thick, was deposited in 2.0 meters of water, and has a lithology code of 1, indicating that it is a sandstone (see below). Note that every thickness and water depth has a decimal point, and that no lithologic code has a decimal point.
Count the number of lines of data you have and write this down somewhere. Save your file when you're finished, and quit your text editor.
Running the program
Make sure your backstripData.txt data file is in the same directory as the Backstrip program. Launch Terminal.app and change your directory to the one with Backstrip. For example, if you have Backstrip in a directory called backstrip on your Desktop, you would type:
In Terminal.app, type the following to launch Backstrip:
The program will will automatically read your data, calculate the backstripping, then display a table of the results. It will also save your data as backstripResults.txt and this file will be located in the same location/folder as the Backstrip program.
Watch the program as it runs to see its progress. After it reads your data it will first write how many lines of data you have. Verify that this matches what you wrote down. Next, it will write the data to the screen; you should verify that the numbers and sequence make sense. For most data sets, it should run very quickly, but it might take up to a few minutes for very large data sets.
The program will then show what it is printing to the output file. The output is in the same order that you typed it: oldest at the bottom, youngest at the top. The first three columns of output are your data, the last column is the total accommodation space accumulated by the end of that layer. In most cases, the a-space column will monotonically increase over time, although it can decrease in some situations. Once the program is finished, press return and the program will automatically quit.
Viewing your results
You can open your data file in Excel or a similar program. Column labels are not included in the output file, but from left to right, the columns are: thickness, water depth, lithology, cumulative accommodation space. Note that this last column is not the space created in any given time step, but the total amount of accommodation space made to that point in time.
Based on your research, assign a numerical data corresponding to the end of each layer, and then you can plot the a-space column on the y-axis and the age on the x-axis. A-space should increase downwards on your plots, and time should proceed from left to right (i.e., oldest on the left, youngest on the right). This may take some fiddling to get your particular program to do this right.
Update notes - version 1.2
Updated to run in the Terminal on OS X 10.10 (Yosemite).
Update notes - version 1.1
This modification eliminates certain rare conditions under which the model would fail to converge and enter an infinite loop. These modifications also speed execution time in all cases.