Palaeogeography, Palaeoclimatology, Palaeoecology
Middle to late Miocene oxygen isotope stratigraphy of ODP site 1085 (SE Atlantic): new constrains on Miocene climate variability and sea-level fluctuations
Introduction
The Neogene period comprises a major change in climate state from relatively global warmth of the early Miocene to colder climates at the end of the Pliocene. As inferred from co-varying δ18O values of planktonic and benthic foraminifers, the general cooling trend in the middle to late Miocene was superimposed by several punctuated periods of intensive glaciations (Mi-Events) which supposedly reflect continental ice sheet growth and/or bottom water cooling (Miller et al., 1991, Lear et al., 2000, Turco et al., 2001, Billups and Schrag, 2002). Due to the scarcity of continuous marine records spanning the middle to late Miocene, a period of widespread erosion in the deep sea (Keller and Barron, 1987), the characteristics of and the control on the Miocene glacial events is controversial. Recently, astronomically calibrated ages for the Mi5 and Mi6 event showed (Turco et al., 2001) that these coincide with periods of low-amplitude variations in obliquity related to the ∼1.2 Ma cycle as proposed by Lourens and Hilgen (1997).
ODP Site 1085 is one of the most expanded and complete middle to late Miocene marine records retrieved from the Southwest African continental margin during ODP Leg 175. In this paper we present a unique high-resolution benthic oxygen isotope record spanning the middle to late Miocene (13.8–7.3 Ma). In addition, an astronomically calibrated time scale based on tuning of a composite Iron (Fe) intensity record from ODP Sites 1085 and 1087 has been constructed. For the first time, this high-resolution δ18O record enables us to decipher the driving mechanisms of the middle to late Miocene climate system in detail. Therefore, this study focuses on the characterization and timing of the Mi-events, the orbital control of δ18O variability, and inferences on sea-level fluctuation during the middle to late Miocene.
Section snippets
Material and methods
ODP Holes 1085A and 1087C were drilled in the Cape Basin during Leg 175. ODP Site 1085 is located at the southwestern African continental margin (Fig. 1) (29°22.47′S, 13°59.41′E, 1713 m water depth) off the mouth of the Orange River, a perennial river discharging into the South Atlantic (Wefer et al., 1998). A continuous hemipelagic sedimentary section composed of nannofossils ooze, diluted by various amounts silt and clay, was recovered from Site 1085 reaching down to the middle Miocene (14
XRF data
In Fig. 2, Fe intensities derived from the XRF core logs of hole 1085A and 1087C, respectively, are plotted versus log-depth (mbsf; Tables 1 and 2). Fe intensities vary between 500 and 6000 cps, and show high-frequency cyclicity. The long-term trend in the Fe intensity data is characterized by six periods of higher Fe intensity located at 433–453, 470–481, 528–537, 547–553, 556–561, and 565–570 m log-depth. These periods correspond to the middle to late Miocene carbonate crash events in the
Miocene isotopic events
The middle to late Miocene open-ocean δ18O record in the investigated time period is punctuated by five episodes of increased values known as the Mi3 through Mi7 events (Miller and Feigenson, 1991, Miller et al., 1991, Wright and Miller, 1992, Wright et al., 1992). These oxygen isotopic shifts have been ascribed to a combination of glacioeustatic sea-level lowering and bottom water cooling of 1–2 °C, but are primarily related to the waxing and waning of the Antarctic ice-sheet (Miller et al.,
Conclusion
The high-resolution benthic stable oxygen isotope data of ODP Site 1085 provide new insight into the middle to late Miocene paleoclimatic evolution. A detailed chronology based on orbitally tuning of a high-resolution Fe intensity composite record has been developed. The long-term cooling trend in δ18O record of Site 1085 approximates the general trend in the global δ18O deep-sea composite of Zachos et al. (2001a) resembling the middle to late Miocene buildup of the East Antarctic Ice Sheet.
Acknowledgments
We are indebted to M. Segl and her team for carefully supervising the stable isotope analyses. We thank A. Wuelbers and W Hale for the help at the Bremen Core Repository. This contribution benefits from discussion with C. M. John, K. G. Miller, J. C. Zachos, and L. J. Lourens. T. Kouwenhoven and K. Billups are thanked for their critical review and suggestions for the manuscript. We thank the Ocean Drilling Program for providing samples. This study was funded by the Deutsche
References (57)
- et al.
The marine oxygen isotope record in Pleistocene corals, Barbados, West Indies
Quat. Res.
(1978) - et al.
Integrated stratigraphy and astronomical calibration of the Serravillian/Tortonian boundary section at Monte Gibliscemi (Sicily Italy)
Mar. Micropaleontol.
(2000) - et al.
Middle Miocene isotope stratigraphy and paleoceanographic evolution of the northwest and southwest Australian margins (Wombat Plateau and Great Australian Bight)
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2004) - et al.
CORTEX, a shipboard XRF-scanner for element analyses in split sediment cores
Mar. Geol.
(1998) - et al.
Long-periodic variations in the Earth's obliquity and their relation to third-order eustatic cycles and late Neogene glaciations
Quat. Int.
(1997) - et al.
Filtering of Milankovitch cycles by earth's geography
Quat. Res.
(1991) - et al.
Middle Miocene high-resolution calcareous plankton biostratigraphy at Site 926 (Leg 154, equatorial Atlantic Ocean): palaeoecological and palaeobiological implications
Geobios
(2002) - et al.
Late Miocene stable isotope stratigraphy of Site 1085: relation to Messinian events
Mar. Geol.
(2002) - et al.
Glacial eustasy during the Cenozoic: sequence stratigraphic implications
AAPG Bull.
(1998) - et al.
Glacioeustatic fluctuations: the mechanism linking stable isotope events and sequence stratigraphy from the early Oligocene to middle Miocene
A Miocene (8–12 Ma) intermediate water benthic stable isotope record from the northeastern Atlantic, ODP Site 982
Paleoceanography
Calibration of Miocene nannofossil events to orbitally tuned cyclostrati-graphies from ceara rise
Climatic importance of the modulation of the 100 kyr cycle inferred from 16 m.y. long Miocene records
Paleoceanography
Reevaluation of the oxygen isotopic composition of planktonic foraminifera: experimental results and revised paleotemperature equations
Paleoceanography
Expeditions into the past: paleoceanographic studies in the South Atlantik
Late Neogene chronology: new perspectives in high-resolution stratigraphy
Geol. Soc. Amer. Bull.
A revised Cenozoic geochronology and chronostratigraphy
Paleotemperatures and ice volume of the past 27 Myr revisited with paired Mg/Ca and 18O/16O measurements on benthic foraminifera
Paleoceanography
Revised calibration of the geomagnetic polarity timescale for the late cretaceous and Cenozoic
J. Geophys. Res.
An astronomically calibrated age model for Pliocene site 1085, ODP Leg 175
Eccentricity forcing of Pliocene–Early Pleistocene climate revealed in a marine oxygen-isotope record
Nature
The Benguela Current and associated upwelling on the southwest African Margin: a synthesis of the Neogene–Quaternary sedimentary record at DSDP Sites 362 and 532
Middle Miocene deepwater paleoceanography in the southwest Pacific: relations with East Antarctic Ice Sheet development
Paleoceanography
Late neogene paleoclimates and paleoceanography in the Iceland–Norwegian Sea: evidence from the Iceland and Vøring Plateaus
Development of composite depth sections for sites 844 through 854
Chronology of fluctuating sea levels since the Triassic
Science
On the structure and origin of major glaciation cycles 2. The 100,000-year cycle
Paleoceanography
δ18O and Marion Plateau backstripping: combining two approaches to constrain late middle Miocene eustatic amplitude
Geology
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