The Mid-Brunhes Transition saw an enigmatic shift towards increased glacial temperature variations about 400 kyr ago. High-latitude Southern Ocean stratification may have been a causal factor, but little is known of the changes to the high-latitude Bering Sea. We generated benthic foraminiferal assemblage data and are the first to document a glacial decrease in episodic primary productivity since the Mid-Brunhes Transition, signifying possible reductions in sea ice summer stratification.

We report the occurrence of a foraminiferal assemblage dominated by Ammobaculoides in the lowermost member of the Middle Jurassic Dhruma Formation exposed west of Riyadh, Saudi Arabia. The new species Ammobaculoides dhrumaensis n.sp. is described from the D1 unit (the Balum Member) of the Dhruma Formation, which has been assigned an early Bajocian age based on ammonites. Our new finding constitutes the oldest reported worldwide occurrence of the agglutinated foraminiferal genus Ammobaculoides.