Evaluating the efficacy of planktonic foraminifer calcite 18O data for sea surface temperature reconstruction for the late Miocene

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doi: 10.1016/j.geobios.2004.12.001
Author(s): Williams, Mark; Haywood, Alan M.; Taylor, Steve P.; Valdes, Paul J.; Sellwood, Bruce W.; Hillenbrand, Claus-Dieter
Author Affiliation(s): Primary:
British Antarctic Survey, Geological Sciences Division, Cambridge, United Kingdom
University of Reading, United Kingdom
University of Bristol, United Kingdom
Volume Title: Geobios
Source: Geobios, 38(6), p.843-863. Publisher: Elsevier on behalf of Université Claude Bernard, Département des Sciences de la Terre, Lyon, France. ISSN: 0016-6995 CODEN: GEBSAJ
Note: In English with French summary. Includes appendices. 93 refs.; illus., incl. 2 tables
Summary: This study examines the efficacy of published δ18O data from the calcite of Late Miocene surface dwelling planktonic foraminifer shells, for sea surface temperature estimates for the pre-Quaternary. The data are from 33 Late Miocene (Messinian) marine sites from a modern latitudinal gradient of 64°N to 48°S. They give estimates of SSTs in the tropics/subtropics (to 30°N and S) that are mostly cooler than present. Possible causes of this temperature discrepancy are ecological factors (e.g. calcification of shells at levels below the ocean mixed layer), taphonomic effects (e.g. diagenesis or dissolution), inaccurate estimation of Late Miocene seawater oxygen isotope composition, or a real Late Miocene cool climate. The scale of apparent cooling in the tropics suggests that the SST signal of the foraminifer calcite has been reset, at least in part, by early diagenetic calcite with higher δ18O, formed in the foraminifer shells in cool sea bottom pore waters, probably coupled with the effects of calcite formed below the mixed layer during the life of the foraminifera. This hypothesis is supported by the markedly cooler SST estimates from low latitudes-in some cases more than 9 °C cooler than present-where the gradients of temperature and the δ18O composition of seawater between sea surface and sea bottom are most marked, and where ocean surface stratification is high. At higher latitudes, particularly N and S of 30°, the temperature signal is still cooler, though maximum temperature estimates overlap with modern SSTs N and S of 40°. Comparison of SST estimates for the Late Miocene from alkenone unsaturation analysis from the eastern tropical Atlantic at Ocean Drilling Program (ODP) Site 958-which suggest a warmer sea surface by 2-4 °C, with estimates from oxygen isotopes at Deep Sea Drilling Project (DSDP) Site 366 and ODP Site 959, indicating cooler than present SSTs, also suggest a significant impact on the δ18O signal. Nevertheless, much of the original SST variation is clearly preserved in the primary calcite formed in the mixed layer, and records secular and temporal oceanographic changes at the sea surface, such as movement of the Antarctic Polar Front in the Southern Ocean. Cooler SSTs in the tropics and sub-tropics are also consistent with the Late Miocene latitude reduction in the coral reef belt and with interrupted reef growth on the Queensland Plateau of eastern Australia, though it is not possible to quantify absolute SSTs with the existing oxygen isotope data. Reconstruction of an accurate global SST dataset for Neogene time-slices from the existing published DSDP/ODP isotope data, for use in general circulation models, may require a detailed re-assessment of taphonomy at many sites.
Year of Publication: 2005
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; DSDP Site 157; DSDP Site 158; DSDP Site 214; DSDP Site 216; DSDP Site 237; DSDP Site 238; DSDP Site 280; DSDP Site 281; DSDP Site 289; DSDP Site 310; DSDP Site 335; DSDP Site 366; DSDP Site 408; DSDP Site 410; DSDP Site 470; DSDP Site 502; DSDP Site 503; DSDP Site 519; DSDP Site 552; DSDP Site 590; DSDP Site 610; DSDP Site 98; Deep Sea Drilling Project; Foraminifera; Global; IPOD; Invertebrata; Isotope ratios; Isotopes; Leg 105; Leg 11; Leg 114; Leg 115; Leg 121; Leg 133; Leg 154; Leg 159; Leg 16; Leg 22; Leg 24; Leg 29; Leg 30; Leg 32; Leg 37; Leg 41; Leg 49; Leg 63; Leg 68; Leg 73; Leg 81; Leg 90; Leg 94; Marine environment; Microfossils; Miocene; Neogene; O-18/O-16; ODP Site 646; ODP Site 704; ODP Site 709; ODP Site 758; ODP Site 811; ODP Site 817; ODP Site 925; ODP Site 926; ODP Site 959; Ocean Drilling Program; Oxygen; Paleoclimatology; Paleoenvironment; Paleotemperature; Planktonic taxa; Protista; Sea-surface temperature; Stable isotopes; Tertiary; Upper Miocene
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Record ID: 2007005709
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