Calcium carbonate concentrations in Miocene and Pliocene sediments of ODP Hole 120-751A

• Main Authors: Wise, Sherwood W, Schlich, Roland
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1992
• Subjects: 120-751A; DRILL; Drilling/drill rig; Joides Resolution; Leg120; Ocean Drilling Program; ODP; South Indian Ridge; South Indian Ocean; Antarc*; Antarctic; Antarctic Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.757589; https://doi.org/10.1594/PANGAEA.757589

Detailed records of % calcium carbonate and calcium carbonate mass accumulation rate (MAR) for Site 751, located on the Southern Kerguelen Plateau, are presented. The shallow-water site contains a Neogene section with well-preserved carbonate sediments. These sediments record variations in the oceanography of the Antarctic surface waters. Carbonate sedimentation patterns reflect changing modes of biogenic sedimentation in the Miocene and Pliocene Antarctic Ocean. Drilling at Site 751 recovered 166 m of early Miocene to Pleistocene siliceous and calcareous biogenic oozes. Three hiatuses, however, were detected: one between 14.8 and 12 Ma, another between 8.9 and 6.7 Ma, and a third between 5.08 and 5.36 Ma. Sedimentation rates were about 20 m/m.y. throughout the Miocene and <10 m/m.y. during the Pliocene and Pleistocene. Key events in the depositional history are as follows: (1) a dramatic decrease in carbonate content, from 75% to near 0%, near the Miocene/Pliocene boundary; and (2) minima in % carbonate occur at 16.7, 16.3, 12.2, 11.7, and 9.8 Ma. The % carbonate record shows variability about a mean of ~70% and then a sharp drop near the Miocene/Pliocene boundary. The carbonate MAR record, however, exhibits a series of steplike changes throughout the Miocene. The terminal Miocene event in the carbonate MAR record is not as dramatic as in the % carbonate record, as carbonate MARs had already decreased to about 15% of their middle Miocene values.