The marine 187Os/188Os record of the Eocene-Oligocene transition; the interplay of weathering and glaciation

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doi: 10.1016/S0012-821X(03)00137-7
Author(s): Ravizza, G. E.; Peucker-Ehrenbrink, B.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 210(1-2), p.151-165. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 62 refs.; illus., incl. 3 tables
Summary: Osmium (Os) isotope analyses of bulk sediments from the South Atlantic, Equatorial Pacific, and the Italian Apennines yield a well-dated and coherent pattern of 187Os/188Os variation from the late Eocene to the early Oligocene. The resulting composite record demonstrates the global character of two prominent features of the low-resolution LL44-GPC3 Os isotope record [Pegram and Turekian, Geochim. Cosmochim. Acta 63 (1999) 4053-4058]. These are: (1) a pronounced minimum in 187Os/188Os (0.22-0.27) in the late Eocene, between 34 and 34.5 Ma, and (2) a subsequent rapid increase in 187Os/188Os, to approximately 0.6 by 32 Ma. An ultramafic weathering event and an increased influx of extraterrestrial particles to the Earth are discussed as alternative explanations for the late Eocene 187Os/188Os minimum. Comparison of the 187Os/188Os to benthic foraminiferal oxygen isotope records demonstrates that the nearly three-fold increase in 187Os/188Os from the late Eocene minimum coincides with the growth and decay of the first large ice sheet of the Oligocene (Oi1 [Miller et al., J. Geophys. Res. 96 (1991) 6829-6848]). The fine structure of the Os isotope record indicates that enhanced release of radiogenic Os, unrelated to the recovery from late Eocene minimum, lagged the initiation of the Oi1 event by roughly 0.5 Myr. This record, in conjunction with weathering studies in modern glacial soils [Blum, in: W. F. Ruddiman (Ed.), Tectonic Uplift and Climate Change, Plenum Press, New York, 1997, pp. 259-288; Peucker-Ehrenbrink and Blum, Geochim. Cosmochim. Acta 62 (1998) 3193-3203], suggests that exposure of freshly eroded material during deglaciation following Oi1 enhanced chemical weathering rates, and may have contributed to ice sheet stabilization by drawing down atmospheric carbon dioxide. The improved temporal resolution and age control of the refined Eocene-Oligocene Os isotope record also makes it possible to illustrate the late Eocene Os isotope excursion as a tool for global correlation of marine sediments. Abstract Copyright (2003) Elsevier, B.V.
Year of Publication: 2003
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Angola Basin; Apennines; Atlantic Ocean; Cenozoic; Climate change; Correlation; DSDP Site 522; DSDP Site 574; Deep Sea Drilling Project; Deglaciation; Depositional environment; Eocene; Equatorial Pacific; Europe; Foraminifera; Glaciation; IPOD; Igneous rocks; Invertebrata; Isotope ratios; Isotopes; Italy; Leg 73; Leg 85; Lower Oligocene; Metals; Microfossils; Nannofossils; Oligocene; Os-188/Os-187; Osmium; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Paleogene; Patterns; Plantae; Platinum group; Plutonic rocks; Protista; South Atlantic; Southern Europe; Stable isotopes; Tertiary; Ultramafics; Upper Eocene; Weathering
Coordinates: N041231 N041232 W1331948 W1331949
S260651 S260650 W0050646 W0050647
Record ID: 2003046356
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands