Rapid change in strontium isotopic composition of sea water before the Cretaceous/Tertiary boundary

The identification of the cause of the marked changes which occurred at the K/T boundary fundamentally depends on the determination of such matters as to whether (1) the development of species extinctions and geochemical changes was gradual (1000-1,000,000 years) or catastrophic (tens to hundreds of years), (2) the anomalies occur precisely at the boundary or precede it, and (3) the chemical and biological changes represent a single event or can be further resolved into several discrete events. Attention is presently given to an analysis of foraminifera from a well-characterized marine K/T section exposed at Bidart, France. A rapid increase is noted in the Sr-87/Sr-86 of ocean water 1.5-2.3 Myr prior to the K/T boundary; this is explainable by a 10 percent increase in the continental Sr flux to the oceans over a 1-Myr period.