Photo Credit Cathleen Benisen
Recent research by Cathleen Benison at West Virginia University, involves direct analysis of air trapped within fluid inclusions of ancient salt deposits (age dated 813,000,000 years ago). This research reveals that oxygen was present in sufficient quantities for life to begin at a time much earlier than previously thought (550,000,000 years ago). This previous age was placed at the Pre-Cambrian and Paleozoic contact and was established using indirect methods of age-dating sedimentary rocks.
Benison's method involves direct analysis of small air bubbles trapped inside fluid inclusions of salt and determined the composition to be 10.9% oxygen. This ground-breaking direct measurement method has confirmed that Earth's atmosphere already had sufficient oxygen to begin to support life about 300,000,000 years earlier than previously thought.
Indirect methods of age dating sedimentary rocks rely on determination of eg. Ar40/Ar30, or Rb/St. The radioactive decay rate of these elements is known therefore by analyzing for these isotopes in a sedimentary rock and determining a concentration for each, one can extrapolate the time required to reach the observed ratio thereby determining the age of the rock.
Maddalena Environmental Inc.