Holocene paleoceanography in the southeast Venezuela Basin, Caribbean Sea

Abstract

Abundance variations of benthic foraminifera in four box cores (3775-4447 m water depth) from the southeastern Venezuela Basin reflect the Holocene paleoclimatic history of the basin. There are no significant but some subtle paleoclimaticl changes during the Holocene. Overall, the following nine dominant calcareous benthic foraminifera species fluctuate down-core but display no obvious stratigraphic trends: Cibicides wuellerstorfi, Nuttallides decorata, Eponides polius, E. turgidus, E. tumidulus, Pullenia quinqueloba, P. bulloides, Melonis pompilioides, and Oridorsalis tener. Primitive species of arenaceous foraminifera are abundant, while more complex forms are rare. Arenaceous foraminifera disappear at 16-18 cm depth in all four cores suggesting that below 16-18 cm the sediment is affected by diagenesis. Significant down-core dissolution of carbonate is seen in the deepest core 68-8 (4447 m). Except core 68-8, the late Holocene is characterized by a higher abundance of the Globorotalia menardii complex, a higher percentage of calcium carbonate, and a greater coarse fraction. Relatively large values for both calcium carbonate and coarse fraction percentages are caused by high productivity in warm surface waters. The late Holocene record of the foraminifera shows greater calcium carbonate dissolution, higher productivity (fertility), and more efficient water mixing during deposition than the early Holocene record. Corrosive bottom water masses are also indicated in the late Holocene by brown color and a high degree of broken planktonic foraminifera. The homogeneity of the southeastern Venezuela basin water mass is responsible for the small variations of S, H(S), and E.