Day four: Dating the Early Stone Age site of Isimila
Here’s a diary of James Cole’s recent research trip to Tanzania as part of a project to date the early stone age site of Isimila.
1st September 2014
Today we worked in the northern branch of the Isimila Karonga where there has traditionally been a long history of Archaeological investigation. The site of Isimila is a site of global importance for understanding Middle Pleistocene hominin behaviour and evolution.
Despite being a site that is cited in almost every major publication on the Palaeolithic of Africa and beyond, with a potted research history from 1920s – 2000s with major excavations being conducted in the 1960’s by Clark Howell of the University of Chicago, the site is still poorly understood in terms of its chronology and broader landscape context. Initial U-series dating work conducted in the early 1970’s returned a date of c.260 thousand years from the middle of the sequence and c.60 thousand toward the top. However, the relationship of the excavated artefacts to these initial dates is far from clear, and the site may indeed be much older. In addition, the site is currently under threat from extreme erosion with a very real danger of losing valuable archaeological and palaeo-environmental information from a key region in the story of human evolution. Our project and the subject of this blog was to therefore engage in a programme of dating the sediments using a technique called Optically Stimulated Luminescence (OSL) which basically measures the last time the sediment was exposed to light.
The last two days spent walking around looking at the geology of the site was done in order to understand the geology that was present there today and try to relate it to those described by the researchers from the 1960’s in order to usefully correlate our fieldwork with their previous dating attempts. And today Martin seems to have successfully worked out the chronology and identified a suitable section for us to start cleaning back tomorrow.