Biogenic opal and carbonate concentration in late Neogene sediments of ODP Site 114-704

• Main Authors: Froelich, Philip N, Malone, P N, Hodell, David A, Ciesielski, Paul F, Warnke, Detlef A, Westall, Francis, Hailwood, Ernie A, Nobes, D C, Fenner, Juliane M, Mienert, Jürgen, Mwenifumbo, C J, Müller, Daniel W
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1991
• Subjects: 114-704; 114-704A; 114-704B; COMPCORE; Composite Core; DRILL; Drilling/drill rig; Joides Resolution; Leg114; Ocean Drilling Program; ODP; South Atlantic Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.754800; https://doi.org/10.1594/PANGAEA.754800

A preliminary composite depth section was generated for Site 704 by splicing Holes 704A and 704B together over the interval 0-350 mbsf (0-9 m.y.). High-resolution carbonate and opal data from the cores were correlated with the calcium and silicon signals from the GST logging run in Hole 704B to identify missing and disturbed intervals in the cores. Paleomagnetic and biostratigraphic age boundaries were then transferred to the composite depth records to obtain an age model, and sedimentation rates were calculated by linear interpolation between datums. Algorithms relating measured dry-bulk density to carbonate content and depth were generated to produce predicted values of density for every sample. Accumulation rates of bulk, carbonate, opal, and terrigenous sediment components were then computed to generate a record of sediment deposition on the Meteor Rise that has a resolution of better than 200,000 yr for the period from 8.6 to 1.0 m.y. From 8.6 to 2.5 m.y., bulk-accumulation rates on the Meteor Rise averaged less than 2 g/cm**2/1000 yr and were dominated by carbonate deposition. The first significant opal deposition (6.0 m.y.) punctuated a brief (less than 0.6 Ma) approach of the Polar Front Zone (PFZ) northward that heralded a period of increasing severity of periodic carbonate dissolution events (terrigenous maxima) that abruptly terminated at 4.8 m.y. (base of the Thvera Subchron), synchronous with the reflooding of the Mediterranean after the Messinian salinity crisis. From 4.8 to 2.5 m.y., carbonate again dominated deposition, and the PFZ was far south except during brief northward excursions bracketing 4.2-3.9, 3.3-2.9, and 2.8-2.7 m.y. At 2.5 m.y., all components of bulk-accumulation rates increased dramatically (up to 15 g/cm2/1000 yr), and by 2.4 m.y., a pattern of alternating, high-amplitude carbonate and opal cyclicity marked the initiation of rapid glacial to interglaci·l swings in the position of the PFZ, synchronous with the "onset" of major Northern Hemisphere glaciation. Both ...