Day 11, June 20th

Day 11, Wednesday June 20th

I spent the morning measuring metal shafts again, so I am not really going to write about that… there just isn’t much to say.

Bridget gave us a lecture about microarchaeology today.  We learned about all of the different techniques that are used in microarchaeology and what they are used for.  Microarchaeology is basically the study of archaeological material at the microscopic level.  There are plenty of things that archaeologists can determine with the naked eye, such as the walls of a structure like the Odeon.  Clearly, a microscope is not needed to see that.  However, there are other important questions that cannot always be answered without the aide of microarchaeology. 

Some of the things that microarchaeologists study are: phosphates, stable isotopes, carbon dating, and microwear.  Phosphates are studied because they can help to determine the use of an item or place.  For example, there are high levels of phosphates left behind from animal and human waste material.  Testing for phosphates can help an archaeologist determine if something they are looking at is a sewer, for example.  Bridget also explained to us that more often that not, microarchaeologists help confirm what is already known.  So, one might suspect that an area acted as a sewer, and with the presence of high levels of phosphates, this can be confirmed. 

Some of the main methods that are used in microarchaeology are: absolute dating, provenance (sourcing), ancient DNA, life history, and site formation processes. 

Bridget started off by talking about is radio-carbon dating.  Everyone knows about radio-carbon dating but I never really understood how it worked until Bridget explained it to us.  There are three types of carbon.  Carbon-12, carbon-13, and carbon-14.  Carbon 12 is the standard form that makes up 98.89% of the carbon in organics.  The isotopes Carbon-13 and Carbon-14 make up the remainder.  Carbon-13 makes up 1.11 percent of the carbon.  Carbon-14 comprises 0.0000000001% of carbon and decays at a regular rate.  By checking the amount of Carbon-14, which has a half life of 5500 years, the time when something lived can be determined with surprising accuracy.  Carbon dating was discovered in 1949, and used to be fairly inaccurate.  However, today it is considered fairly reliable and is often considered an important piece of the puzzle when it comes to determining the age of something.  Bones, charcoal, seeds, and organic matter can be dated.  Although these may not be the most important items when it comes to archaeology (nothing turns an archaeologist on like bits of pottery!), they can be used to help determine context, which is crucial to putting the puzzle together. 

Provenance, or sourcing, helps archaeologists to determine the source of an item by looking at the chemical composition.  Ashkelon is on a major trade route, and as such, has various items from all over Europe, North Africa, and Asia.  By studying the chemical composition of certain objects, their point of origin can be determined (only to a certain extent and depending upon the uniqueness of the composition).  Another piece of the puzzle. 

Ancient DNA is also something that is looked at whenever possible.  It has helped us to answer big questions about the origins of mankind, but also answers more specific questions.  In the case of Ashkelon, the Roman infant sewer or dead-baby sewer is a good example.  The sewer, which I believe I mention in a previous post, contained the bodies of quite a few infants under what is suspected to be a brothel.  The bones that were able to be tested were, to help answer a couple of questions.  The biggest question is why were these newborn babies discarded in the sewer system.  Infanticide was suspected, but in the case of infanticide, it is more likely that the babies would be females (in a patriarchal society).  In the case of the Ashkelon sewer, most of the infants were males, and so it seems unlikely that infanticide was practiced there. 

Well, you may ask… how do we know Ashkelon was a patriarchal society?  Microarchaeology helps us to answer that question as well.  In the case of the Caananite burial chamber, the remains of several families were found.  They were tested to see how the chambers were grouped.  Based on the evidence that was found there, it was determined that Ashkelon was probably a patriarchal society.  This is because the women were found buried with their husbands families.  The males of the various chambers seemed to be related somehow, while the females DNA indicated that they all came from different families. 

Soil can also play an important role in archaeology.  When you are doing archaeological fieldwork, it is important to pay attention to differences in soil types.  Using a patiche, you flatten the sides of a probe or area so that you can differentiate the types of soil more easily.  Some samples are collected and run through the FTIR machine in the in-field lab others are evaluated using micromorphology, which I will come back to in a moment.  The FTIR (fourier transform infrared spectrometer) can help to determine different things about the sediment that is tested.  For example, it can determine if the sediment has been heated or not.  It can also help to get an idea of the general composition of unknowns. 

For micromorphology, a chunk is taken out of the beautiful flat walls that are made to help see the layers of sediment.  They cut a square around the sample and cover it in plaster.  Once this is done, samples are cut out and taken by the microarchaeologists for study.  They cover an area with plaster before removing it and add in some kind of resin that solidifies the soil sample.  The whole process takes about three months.  Once the sample is solidified, sections are cut out and looked at under a microscope.  This is very helpful for a number of reasons.  The differences that are not apparent to the naked eye become much more obvious under a microscope. 

One of the things that raises questions in the sediment sample is the presence of white layers.  There are many different things that could make up white layers, such as chalk, plaster, ash or phytoliths.  White layers that were originally thought to indicate a plaster floor might, in fact, be layers of phytoliths.  Phytoliths are part of plants that can be used to determine what kinds of plants were present in an area.  For example, Bridget was telling us about an area that they had tested previously.  There were several white layers that were believed to indicate plaster flooring.  The building that they were found in was believed to have been some kind of public building or public office.  However, upon examination of the sediment sample, it was determined that several of the white layers were not plaster floors.  Due to the high presence of certain phytoliths, they were able to determine that this big public building was not a big public building at all.  It was more likely that at some point it served as a stable for sheep or goats.  

It was all really interesting stuff and I wish I wasn’t so tired all the time so that I could make this all sound a bit more coherent!