The causes and mechanisms of short-term reversals and excursions like the Jaramillo, as well as the major field reversals like the Brunhes–Matuyama reversal, are subjects of study and dispute among researchers. One theory associates the Jaramillo with the Bosumtwi impact event, as evidenced by a tektite strewnfield in the Ivory Coast, though this hypothesis has been claimed as "highly speculative" and "refuted". A later study found the deposition of the Ivory Coast strewn field and the onset of the Jaramillo reversal not to be contemporaneous as previously inferred. They are separated in time by 30,000 years.