The grayish volcanic tephra is unique to each eruption and can be identified microscopically.
Tephra analysis was carried out in order to observe possible isochrones, which were then used to form a relative chronology.
Initial results suggest a clear developmental sequence on the flows that have not been disturbed by tephra deposition.
The majority of tephra horizons within a sequence can be distinguished on the basis of major or trace element chemistry.
As the tephra layers can also be accurately dated you have a great series of time points to assign any fossils to.