title: A molecular organic carbon isotope record of miocene climate changes.
abstract: The difference in carbon-13 ((13)C) contents of hopane and sterane biomarkers in the Monterey formation (Naples Beach, California) parallels the Miocene inorganic record of the change in (18)O (delta(18)O), reflecting the Miocene evolution from a well-mixed to a highly stratified photic zone (upper 100 meters) in the Pacific. Steranes (delta(13)C = 25.4 +/- 0.7 per mil versus the Pee Dee belemnite standard) from shallow photic-zone organisms do not change isotopically throughout the Miocene. In contrast, sulfur-bound C(35) hopanes (likely derived from bacterial plankton living at the base of the photic zone) have systematically decreasing (13)C concentrations in Middle and Late Miocene samples (delta(13)C = -29.5 to -31.5 per mil), consistent with the Middle Miocene formation of a carbon dioxide-rich cold water mass at the base of the photic zone.
authors.forename: M
authors.initials: M
authors.lastname: Schoell
authors.forename: S
authors.initials: S
authors.lastname: Schouten
authors.forename: J S
authors.initials: JS
authors.lastname: Damsté
authors.forename: J W
authors.initials: JW
authors.lastname: de Leeuw
authors.forename: R E
authors.initials: RE
authors.lastname: Summons