Benthic foraminifera as a tool for exploring the geographical extent of a sediment drift in the Cipero Formation, Trinidad, SE Caribbean

Abstract

Research on sediment drifts (the non-genetic term for contourites) is becoming increasingly popular due to their economic potential and usefulness as records of past climate and bottom water circulation changes. We examine the geographical extent of a sediment drift at the Cipero Formation, Trinidad (Cipero-1 site) using benthic foraminifera to measure (1) winnowing, based on the statistical similarity of replicate >63 and >106 μm samples, (2) bottom current action using the abundance of Planulina wuellerstorfi, and (3) down-slope transport, based on the occurrence of allochthonous shallower-water species. We compare this previously published data with new benthic foraminiferal data collected at two other locations (Cipero-2 and Cipero-3 sites).All three exposures consist of cream marls and were laid down at ≥2000 m palaeodepths during the Middle Miocene. We confirm the Cipero-1 exposure was a sediment drift based on an enhanced bottom current that traveled parallel to the palaeo-slope, good sorting, and no shallower-water foraminifera. The Cipero-2 and Cipero-3 sites were not sediment drifts. Both sites experienced sluggish bottom water circulation but were palaeoenvironmentally dissimilar. The Cipero-2 samples were not winnowed and experienced down-slope transport, indicated by Cibicidoides compressa, Cibicidoides crebbsi, and Triloculina trigonula.We present the first model showing possible influences of coastal upwelling at the Cipero Formation. Our Cipero-3 site experienced a possible episodic impulse of phytodetritus based on increased abundances of Siphonodosaria pomuligera and Globocassidulina subglobosa. Palaeoenvironmental proxies showed the Cipero Basin as generally cold, nutrient deficient and high oxic, reflective of the proto-North Atlantic Deep Water.