Complex sentence: Geoffrey then went to York, where he refused to make Burchard treasurer before the archiepiscopal election had been ratified by the papacy, a stance supported by the majority of the York cathedral chapter.
Split into simpler sentences: Geoffrey then went to York, where he refused to make Burchard treasurer before the archiepiscopal election had been ratified by the papacy. These actions were supported by the majority of the York cathedral chapter.