I am studying a sedimentary basin and there are sediments missed during an uplift episode, I have 3 wells with %Ro values and I want to estimate the amount of the erosion for each well.
Dear Mr. Ali,
vitrinite reflectance is a subtle tool for metamorphic and diagenetic processes. In the present case the statistical variation is rather high around 0.6 %. How much time to you expect within the hiatuses ? I think that in this case it would have meant to overstress this method. It is not only the thickness which is unknown but also the lithology, texture/structure and the physical parameters such as heat flow, conductivity..... You may get differences for the various hiatuses which you would like to correlate with thickness according to your trend line and in reality it might be due to some of the factors I mentioned above some of which are controlling the Ro values. You must reduce the number of unknowns to one unknown, otherwise you may not obtain reliable results.
I wish you much success
H.G.Dill
Dear Dr. Harald G. Dill
First of all, I,d like to thank you for your answer. secondly, there is a huge gap between the Maastrichtian deposits (66 Ma) and the Pliocene-Pleistocene deposits (5-3 Ma) and about 60 Ma gap according to the biostratigraphic results. for the type of lithology, there are 3 formations equivalent to the missed period and composed mainly of shale and limestone.
at the moment I am studying the tectonic evolution of this basin and I need to estimate the thickness of the eroded section. unfortunately, I do not have any Apatite fission track analysis.
Do you have seismic data or well logs. Either/ both of these may help you. The latter, using the normal compaction curve overlay
Assuming that Vr=0.6 equates to say 90 degrees Celsius and that the geothermal gradient for the area of interest is 3 degrees C per 100 meters, it is obvious that a Vr of 0.6 at a measured depth of around 1500 feet (~450 m) implies uplift on the order of 1,5 to 2 km ( figure depends on the assumed surface temperature). Please also bear in mind the error bars on the Vr measurement which can be very large ( eg the deepest data point on your plot looks unrealistic to me).
Dear Dr. Lukman Mobolaji Johnson
Many thanks for your answer.
I have 2D seismic data and well logs. I created the tectonic subsidence curves. but I couldn't estimate the eroded thickness.
regards.
Dear Dr. W.J.E. Van de Graaff
Many thanks for your answer. I will apply your method.
For the %Ro values. all the values of the Barremian sediments in the four wells are very small compare to the above sediments and I do not why!
regards,
Moamen
Hello Moamen,
if you indicate in the figure in your original post the boundaries between the different stratigraphic intervals ['Barremian', 'Maastrichtian', 'Pliocene'] + provide more detailed info about the material on which the Vr reflectivity was measured (e.g. photos of the particles, all measurements done by the same laboratory with the same equipment and the same analyst in a single set of analysis - or alternatively done by different analysts / different equipment / etc ] I may be able to comment further
Moamen Ali have a look at the methods in this paper and some of the references in it that have discussed the compaction method of estimation. You may compare your outputs with the output from VR
Article A new approach for estimating the amount of eroded sediments...
Dear Dr. W.J.E. Van de Graaff
Firstly, I'd like to thank you for your comment. Secondly, I can't provide more detailed info about the material on which the Vr reflectivity was measured because I am a researcher, I received the data from a petroleum company and I am not allowed to get info like that.
regards,
Moamen
Dear Dr. Lukman Mobolaji Johnson
Many thanks for your help, I'll read the mentioned paper and try to apply the discussed method.
regards,
Moamen