Geochemical

Over the years there have been a number of theories about the Cambrian Explosion. The researchers said that those concepts, which fall into three main categories — geological, geochemical and biological — are separate and exclusive processes that also suggest a single cause of the explosion.

Source: tatoeba (12260309)

Geochemical tests also showed that a patch of reddened clay had been heated to temperatures of over 700C (1292F) with repeated fire-use in the same location of the site.

Source: wiktionary