Oxygen- and carbon-isotopes at DSDP Leg 73 Holes

• Main Authors: Weissert, Helmut J, McKenzie, Judith A, Wright, R, Clark, Murlene W, Oberhänsli, Hedi, Casey, Martin
• Format: Dataset
• Language: English
• Published: PANGAEA 1984
• Subjects: 73-519; 73-521; 73-522; 73-523; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Leg73; South Atlantic/HILL; South Atlantic/PLATEAU; South Atlantic/RIDGE; Antarctic; The Antarctic; Antarc*
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.811212; https://doi.org/10.1594/PANGAEA.811212

We established a composite oxygen- and carbon-isotope stratigraphy for the Pliocene in the central South Atlantic. Monospecific samples of benthic and planktonic foraminifers from pelagic sediments from DSDP Sites 519, 521, 522, and 523 were analyzed isotopically. The resulting benthic oxygen-isotope stratigraphy allowed three paleoclimatic periods in the Pliocene to be distinguished. During the early Pliocene (5.2-3.3 Ma), low-amplitude climatic changes prevailed in a world that was less glaciated than during the Pleistocene. A net increase in global ice volume is documented in a 0.5 permil positive shift in the average 18O composition of the benthic foraminifers at 3.2 Ma. The middle Pliocene (3.3-2.5 Ma) is not only characterized by a more widespread glaciation of the Southern and Northern hemispheres but also by more drastic isotopic differences between glacial and interglacial times. A minor shift in the average 18O composition of the benthic foraminifers marks the beginning of the late Pliocene-early Pleistocene climatic period (2.5-1.1 Ma). Alternating cold and warm climate is documented in both the oxygen-isotope record and in the pelagic sediments. During cold periods, sediments with a lower CaCO3 content indicate more corrosive bottom-water conditions. More negative 13C signals in the benthic foraminifers from these sediments suggest that the Antarctic Bottom Water current was intensified in glacial times. The oxygen-isotope composition of the measured planktonic foraminifers suggests that the surface water in this part of the South Atlantic remained relatively warm during the growth of the Pliocene glaciers.