Other data sources - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 203

recent cycles had greater amplitude and longer cycle length ( 100,000 years vs.
41,000 years). Martinez-Garcia et al. (2011) suggested that increasing dust and
iron levels after 1.2 mybp contributed to this transition. Whether the transition
produced additional dust and iron, which in turn provided a positive feedback, or
whether additional dust and iron from some cause contributed to the transition is
dicult to resolve.