June 21, 2007 Meeting
Joint with the Younger Chemists Committee
Ruth Ann Armitage Ruth Ann Armitage

Associate Professor of Chemistry,
Eastern Michigan University
Ypsilanti, MI

"Archaeological Chemistry of Rock Paintings: Radiocarbon Dating and Chemical Analysis"

Date:  June 21, 2007
Location:    Viceroy of India
19W555 Roosevelt Rd
Lombard, IL
(630) 627-4411

Cost:  $28.00 for members of ACS and their guests, $30.00 for non-members,
     $14 for students or unemployed

Dinner reservations are required and should be received in the Section Office via phone (847-647-8405), fax (847-647-8364), email (, or web by noon on Tuesday, June 19.   PLEASE HONOR YOUR RESERVATIONS.  The Section must pay for all dinner orders.  No-shows will be billed.


5:00 - 6:00  PM Job Club
5:30 - 6:30  PM Social Hour: 
6:30  PM Dinner

Topic: "Archaeological Chemistry of Rock Paintings: Radiocarbon Dating and Chemical Analysis"

Abstract: Rock paintings, or pictographs, are unique cultural remains that are difficult to place into archaeological contexts because they are not a part of the buried stratigraphic record of a site. Direct radiocarbon dating of the paint itself would ideally be used to determine their age. The paint is typically an inorganic pigment (iron oxides and hydroxides are common) presumably mixed with an organic binder or vehicle to make the paint flow and adhere to the rock surface. Dating rock art by conventional radiocarbon techniques would have required completely destroying the paintings; the advent of accelerator mass spectrometry (AMS) for direct measurement of 14C changed that. A plasma-chemical oxidation method was developed in the 1990s to selectively remove organic carbon from small samples of paintings, yielding CO2 for radiocarbon analysis by AMS. Some paintings contain easily recognized organic material, such as charcoal, but most do not. At EMU, we are using chromatographic methods to determine the nature of the organic material present in rock paintings, and using the plasma-chemical oxidation/AMS method to date them. Results of our work on paintings from sites in Idaho, Texas, Guatemala, and other locations around the world will be presented.

Biography: Ruth Ann Armitage earned a B.A. in Chemistry from Thiel College (Greenville, PA), and completed a Ph.D. in Analytical Chemistry at Texas A&M University on radiocarbon dating of charcoal-pigmented rock paintings. Since 2001, Dr. Armitage has been on the chemistry faculty at Eastern Michigan University. She and her students are currently using such analytical methodologies as GC-MS and ATR-FTIR to characterize and date by plasma-chemical oxidation-AMS archaeological materials, including rock paintings, fragile organic artifacts, and residues.

Map and Directions

Parking:   Free


The dinner will be served buffet style.

Updated 5/26/07