I'm working on geological model of an alluvial fan in the Red Sea. I found one and half sequence in the upper 90 meters of a fan. I have one sample from each meter in depth.
Is that Quaternary? or it contain a portion of Pliocene?
At the upper most, should I have highstand tracts?
Dear Ahmed
To confirme the age and limite of this delta you should make carbone 14 datation by using organic mater or mollusque fragments found in its layers. or using U/Th analysis.
generally the deltas is classified as quaternairy deposits, we can find a very well cimented deposits near the beach classed as recent formations, and a very old formations not cimented classed as paleozoic. in deltas area we can get very big thikness in very short time.
good luck
Dear Ahmed
personally, I think it is difficult to apply sequence stratigraphy on alluvial fans. Alluvial fans in the Levant and at the Arabian Peninsula are nice archives, but often used only because for their terrestrial record.
But answering your questions:
You can expect a lot of facies changes in such a system. Not only triggered by HST and LST, but also by climate driven erosion independent from sea level change, and in that region more important, geomorphological gradients driven by tectonics independent from climatic or transgressional factors, too. Where exactly are you working?
To define the age absolutely, you can use some of the methods Smaine suggested, if you find the material you need for dating and they are not effected by taphonomy or diagenesis (I did not expect you will find useful material in a core, but maybe some fossil corals). If you are lucky you will find some artifacts, which can give you a maximal indirect age, or some soil horizons you can maybe correlate with major climatic shifts in your working area. Without that, it could be anything in the fan: Holocene, Pleistocene, Pliocene. Be a bit more specific with the area you are working in, and others con be more specific with their answers.
There are some useful sedimentological studies from southern Jordan and from the Gulf of Elat, and also papers about the pleistocene reefs of egypt. From the other countries the scientific record is sparse and sometimes not very reliable (as far as I know).
Good luck
Johannes
Please, begin to see "Alluvial fans and their environments" in R. Cooke, A. Warren and A. Goudie, Desert Geomorphology, Chapter 12, and multiple other contributions in bibliography
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