Complex sentence: There has been much debate on how these mud mounds were formed, one theory led to them being called reef knolls, knoll reefs, or bioherms but work in 1972 by Miller & Grayson explained their structure.
Split into simpler sentences: There has been much debate on how these mud mounds were formed. One theory led to them being called reef knolls, knoll reefs, or bioherms but work in 1972 by Miller & Grayson explained their structure.