Upper Cretaceous (Turonian–Santonian) Haplophragmoides from IODP site U1512, Great Australian Bight

Abstract

Results from the International Ocean Discovery Program (IODP) Site U1512 in the Great Australian Bight offer insights into climate immediately after the peak of the Cretaceous hothouse. Lower Turonian to Santonian deposits yield a unique high-resolution micropaleontological record of the Australo-Antarctic Gulf that is dominated by agglutinated foraminifera. The complex paleoenvironment at Site U1512 illustrates a constantly changing marine setting characterized by the interplay of runoff from the vast Ceduna River system to the north and varying degrees of influence of the Indian Ocean.

A common element in the agglutinated foraminiferal assemblage is the genus Haplophragmoides, which represents between 20 and 40% of the total benthic foraminiferal assemblage, and its occurrence seems particularly common in intervals with higher terrestrial influx. Like many agglutinated foraminiferal assemblages, the agglutinated taxa at Site U1512 suffer from preservational issues. In addition to effects during early diagenesis, like the degradation of organic cement, the delicate planispiral taxa especially experienced extensive deformation, which can affect the correct identification of taxonomically relevant features. Among the six species of Haplophragmoides that represent most of this genus at Site U1512, we identify and describe three new species: H. petaliformis n.sp., H. tenellulus n.sp., and H. antarcticus n.sp.