Fritz Theyer

Benthic foraminiferal trends, Pacific-Antarctic basin

Abstract Benthic foraminiferal communities, living in depths of about 3000–5100 m in the Pacific-Antarctic Basin, consist mostly of cosmopolitan abyssal species. The assemblages are generally over 85% arenaceous in composition; a few, however, from depths of 3000 to 4000 m, are predominantly calcareous. Correlative with the uniformity of the environment, faunal trends, if present, are poorly developed. Four bathymetric foramineral groups can be distinguished considering the upper depth limits (UDL) of occurrence of prominent species: 1. 1. Hyperammina subnodosa Brady , UDL ≥ 4000 m; 2. 2. Reophax pauciloculatus Rhumbler, UDL ≥ 3800 m; 3. 3. Hormosina robusta Pearcy, UDL ≥ 3000 m; 4. 4. Cyclammina pusilla Brady, UDL ≥ 3000 m. Frequency changes in the above groups define two faunal boundaries: one at 3500 m, and a second, weaker one, at 4800–5000 m. Among ten species selected because of their abundance in western Antarctic seas, Recurvoides contortus Earland has the widest depth range (20–6200 m), and Hormosina robusta Pearcy has the narrowest one (3000–5100 m). Cribrostomoides subglobosus (Sars) and Cyclammina pusilla Brady are most abundant in the bathyal and abyssal zones of the western Antarctic sector.

Pleistocene Climates in the Atlantic and Pacific Oceans: A Reevaluated Comparison Based on Deep-Sea Sediments

Variations of the Globorotalia menardii complex in cores from the Indian Ocean can be interpreted as indicating climatic changes that are opposite to trends exhibited by the total planktonic fauna. The questionable value of correlations between different water masses based on a single species can be shown by Neogloboquadrina dutertrei subcretacea in cores obtained off the coast of California and Baja California. This information, in addition to previous correlations between Quaternary cores of the Atlantic and Pacific oceans, indicates that the Pleistocene history of the two oceans was parallel.