Radiolarian relative abundance and opal and radiolarian accumulation rate from IODP Site 306-U1314

• Main Authors: Hernández-Almeida, Iván, Bjorklund, Kjell R, Sierro, Francisco Javier, Filippelli, Gabriel M, Cacho, Isabel, Flores, José-Abel
• Format: Dataset
• Language: English
• Published: PANGAEA 2018
• Subjects: 306-U1314; Accumulation rate; opal; radiolarians; Actinomma boreale; Actinomma leptodermum; Actinomma medianum; AGE; Botryostrobus auritus/australis; COMPCORE; Composite Core; Cornutella profunda; Cycladophora davisiana; Druppatractus variabilis; Exp306; Integrated Ocean Drilling Program / International Ocean Discovery Program; IODP; Joides Resolution; Larcopyle buetschlii; Larcopyle weddellium; Larcospira minor; Lithocampe platycephala; Lithomelissa setosa; Lithomelissa thoracites; Lithomitra lineata; North Atlantic; North Atlantic Climate 2; Phorticium pylonium; Porodiscus sp.; Pseudodictyophimus gracilipes; Spongodiscus spp.; Spongopyle osculosa; Spongotrochus glacialis; Stichocorys seriata; Stylochlamydium venustrum; Stylodictya validispina; Arctic; Atlantic Arctic; Atlantic-Arctic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.891191; https://doi.org/10.1594/PANGAEA.891191

A high-resolution record of radiolarian assemblages from Site U1314 was studied to reconstruct hydrographic and climatic changes in the North Atlantic Ocean during the Mid-Pleistocene Transition period (1069–779 ka). Besides the faunal record, absolute accumulation of radiolarians and total biogenic opal are used to determine changes in surface water productivity. Results show that the North Atlantic Arctic Front shifted back and forth repeatedly at a glacial/interglacial timescale, bringing the site under the influence of both cold Arctic (glacial), and much warmer Atlantic (interglacial) waters. During glacial intervals and “ice-rafted debris” (IRD) events, the deep-dwelling taxon Cycladophora davisiana was the greatest contributor of the radiolarian assemblage, suggesting cold surface conditions, melt-water discharge and changes in deep and intermediate circulation. Interglacial intervals were characterized by abundant shallow-dwelling taxa like Pseudodyctiophimus gracilipes and Lithomelissa setosa, increased opal accumulation, and higher radiolarian diversities, indicating a northward flow of warm Atlantic surface waters to the Site U1314 area. A marked change in the structure of the radiolarian assemblage occurred after MIS 22 (~ 860 ka), with large taxa differences between warm and cold periods, probably in response to changing ocean conditions due to the higher amplitude of glacial/interglacial changes as the dominant periodicity of high-latitude climate oscillations shifted from 41-kyr to 100-kyr. Thus, we conclude that the radiolarian assemblage from the North Atlantic have changed drastically along with variations in ocean circulation in response to orbital and millennial-scale climatic variations that occurred in the Early and Mid-Pleistocene.