I have several marine sediment cores from the Devonian period, from North America. I scanned them with XRF, and I found high content of Ca. I have several questions:
1- What elements should I look for when doing analysis; I already using Ca, Ti and Fe (for seasonality), Sr, Si, K, Sr, and S (because I see some pyrites under the microscope), are these enough or I need to include more?
2- One of my supervisor's questions is determining the time, like how many years I can get the data?
3- Do I need to run some Statistical analysis on the data like PCA, Regression etc...?
4- There are many cracks in the cores so we covered them with masking tapes, which impact the data, is there any method using software like R to clean the data and eliminate the masking tape's data?
5- How I can interpret the bioturbation, like from my data what can be used to help me understand the cause of the bioturbation? from the images, you can see the sediments go from bioturbated to laminated?
6- If you have any paper or book please suggest some for me?
here some example of my core: I included one bioturbated sediment and the another one is Laminated. These are core images with some elements, my friend helped me plot them just to test the data.
I have just a comment for your data treatment. Are you decomposing your x-ray spectra into the different fluorescence peaks and background contributions or do you simply plot region of interests? If you do the latter, you have to be careful because there can be serious line overlap e.g. for Al and Si if there is a strong Si signal present. From looking at your data, the Al and Si look quite similar so I would encourage you to check this.
To be honest, I did not do the scan myself; I jut got the data from my supervisor. However, I want to use some elements that help me to determine cyclicity in these sediment cores and try to figure out what could cause the bioturbation. In general, I have no idea of what treatment my supervisor have done.
Hello Majed,
It looks like your selection of elements is already made and the elements chosen are good. The only one you really need is Mg, possibly Na. If you want to match your core to spectral electric logs choose U, K, Th. It looks like much of your core is argillaceous limestone (marlestone?) with shaley stringers. That is why you need magnesium to see if there is dolomite in the core. As to the tape question, I think it can not be resolved, the depth of penetration in XRF data is very shallow. Next time take the tape off, its not like its holding broken fragments together and the "holes" will not goof up the XRF like tape.
If you want more detailed answers on bioturbation take some close up pictures of the more common bioturbation. George Pemberton has some good literature on bioturbation and would probably be willing to help you if you had specific questions.
Cheers,
Paul Grover
Hi Dr. Grover, thank you very much for your reply and suggestion. I was against using the masking tapes, but my supervisor had different opinion at that time.
Dr. Towe,
I am conducting a chemostratigraphy on these cores, and since I am new in this field I made my elements selection based on few papers and my supervisor's idea. Basically, no one has conducted any XRF based study on these cores.
the main idea is to reconstruct the paleoenvironment or paleoclimate conditions from the ITRAX data, such looking or trying to estimate the sedimentation rate, seasonality etc.. to come up with the new study (for me) as a part of my Ph.D. project.
Dear Mr. Turkistani,
chemostratigraphy or chemical-based environment analysis are always high up on the agenda because of the data provision and the easy-to-use data management. Some may even called it the philosopher´s stone. I support such an approach, but do not restrict your work to the chemical or physical compartment only and compare the unknown with the unknown. Calibrate your findings to a good geological (sedimentology, structures, texture) and mineralogical (light, heavy minerals, phyllosilicates) and even paleontological yardstick. If you do not (yet) have the expertise try and contact someone for assistance it is better to go a way like this with someone else than alone trusting in numbers.
I wish you much success
H.G.Dill
Did you mean that you advisor wanted to know about the relative time interval represented in the core?
Dear Majed,
In my opinion for chemostratigraphy and paleoenvoirment reconstruction it is important to determine the redox sensitive trace elements (Cr, Mo, Re, U, V, Cu, Ni, Zn, As). They can be used as forensic elements to determine anoxic contions at the time of depostion. For Oxic conditions Mn is a good indicator. I would also try to plot ratio correlation plots to see trends.
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