Geological and Geochemical Analysis of Nile Sediments and Ancient Ceramics - Dr Hany Hamroush

Edited 26th Jan, Dr Hany sent me an email correcting my notes and I have reposted his corrected version. It was so nice of him to do this and much appreciated.

January 21st, 2008 Geological and Geochemical Analysis of Nile Sediments and Ancient Ceramics – Dr. Hany Hamroush

This was one of the not to be missed lectures. Dr. Hany was a superb communicator who brought the complicated subject to life and made it fascinating. He is very well qualified and has worked with many equally well qualified geologists and archeologists such as Prof. Rushdi Said, who wrote the best geology references about the geology of Egypt and the river Nile in Egypt as well as the late Dr. Michael Hoffman, who went to Egypt for the first time in 1969 as participant in the American Museum of Natural History’s Hierakonpolis Expedition. He helped in the excavation of the ancient city of Nekhen and spent time at the locality of HK14. This was the first excavation of a Predynastic Upper Egyptian settlement (i.e., just before the unification of Egypt and the rise of the first State in History) in over 35 years. Dr. Michael Hoffman is the author of “Egypt before the Pharaohs”. Also, Dr. Hamroush was able to pursue his research career under the supervision and support of Prof. Ralph Allen of the University of Virginia who is one of the main founders of Archaeological Geochemistry in the States.

The lecture was sufficiently complicated that I think without his slides my notes make no sense, so I will summarize.

The Nile has two main sources from three main tributaries (the Blue Nile & the Atbara river from Eastern Africa and the White Nile from Central Africa) and then flows for more than 2000 km without any further inlets. This makes it suitable for analyzing and identifying its deposits: sand and mud as to their source. So you can find out whether the main deposits were coming from Central Africa or East Africa. The rocks of central Africa are of Precambrian age and mainly of granitic composition but those from East Africa are from the Tertiary age of basaltic composition. Natural weathering and transportation of these rocks mean that their broken fragments ( i.e., sand and silt size fractions) and their chemically altered fragments (i.e., clay size fraction) flow down to the delta. Dr. Hany has investigated Nile sediments of all ages and by ordinary physical methods it is impossible to identify differences. They apparently all look the same. The physical characteristics are as follows:

• Gravel – non existent

• Sand (2 mm – 0.063 mm) – significant amounts

• Mud (0.063 – 0.004 mm) – majority

However, the source of the sand grains and their composition can be identified by analysis of their light mineral fraction while heavy minerals in the sand size are so sparsely present as to be unfairly represented in the sample. The trace elements in the light sand fraction give you a chemical fingerprint detectable by advanced techniques such as Instrumental Neutron Activation Analysis (INAA) and can be related to the relative contribution of the sediments from the two sources mentioned above as a function of time. It should be noted that the clay fraction, which is the principal component of Nile mud, is produced by Chemical weathering of the original rock materials which can alter their authentic chemical composition. So Dr. Hamroush analyzed sand grains of only a certain size and composition which means he was able to identify Nile sediments from different times.

He was able to draw a graph showing the variation of selected trace elements in sand size grains of Nile sediments over time to indicate whether they had come from central Africa or eastern Africa.

With the collaboration of Prof. Daniel Stanley of the U.S. Natural History Museum who dug several bore holes in the Nile delta to a depth more than 40 meters, Dr. Hamroush tested his proposed model further. Analysis of the cores showed that when you have a high lanthanum over lutetium (La/Lu) ratio in the light sand fraction of Nile sediments, then this means a larger volume coming from central Africa whereas a high Chromium over Scandium ratio (Cr/Sc) means Ethiopian origins. The time period covered was 25,000 -3,000 BP (before present). He was able to define the relative contribution of the sediments of the two sources as a function of time and to correlate this to the level of the Mediterranean Sea and the development of the Nile Delta at the time. A rise in sea level coupled with lots of Nile sediments from its sources meant that the sediments had fanned out forming the delta area.

Ceramics

The impact of all this on ancient ceramics is a multidisciplinary field. Using a variety of techniques such as

• Petrography and microscopic studies

• SEM-EDX

• X Ray diffraction

• INAA

He was able to chemically analyze various ancient samples of pottery from the Neolithic and Predynastic periods and determine the raw materials used to make it and whether it was local to the area or not. Such analysis could be used to trace bartering and exchange of pottery in various places.

It was a fascinating lecture and a whole new area for me. It would be interesting to see the analysis of organic materials being fitted into this as well.

Dr. Hamroush ended the lecture by saying that although this model was developed through years of research with his professors, he is still faced with the challenge that the industry of manufacturing ceramics was a highly localized activity. Therefore there is a need to measure the geochemical characteristics of all the possible clay sources in Egypt and its potential neighboring sources before starting the reconstruction of ancient exchange (REAL TRADE) patterns.

This entry was posted on Monday, January 21st, 2008