Is the structure of this sentence correct?
"The time span of the site, the presence of volcanic tuff, and the high probability of finding pig fossils in the area all influence the choice of dating methods."
I am particularly concerned about the "in the area bit". Does it mean "the time span of the site in the area + the presence of volcanic tuff in the area + the high probability of finding pig fossils in the area" or just "the high probability of finding pig fossils in the area"?