Data report: multiproxy geochemical characterization of OAE-related black shales at Site 1276, Newfoundland Basin

Abstract

During Ocean Drilling Program Leg 210, a greatly expanded sedimentary sequence of continuous Cretaceous black shales was recovered at Site 1276. This section corresponds to the Hatteras Formation, which has been documented widely in the North Atlantic Ocean. The cored sequence extends from the lowermost Albian, or possibly uppermost Aptian, to the Cenomanian/Turonian boundary and is characterized by numerous gravity-flow deposits and sporadic, finely laminated black shales. The sequence also includes several sedimentary intervals with high total organic carbon (TOC) contents, in several instances of probable marine origin that may record oceanic anoxic events (OAE). These layers might correspond to the Cenomanian–Turonian OAE 2; the midCenomanian event; and OAE 1b, 1c, and 1d in the Albian. In addition, another interval with geochemical characteristics similar to OAE-type layers was recognized in the Albian, although it does not correspond to any of the known OAEs. This study investigates the origin of the organic matter contained within these black shale intervals using TOC and CaCO3 contents, Corg/Ntot ratios, organic carbon and nitrogen isotopes, trace metal composition, and rock-eval analyses. Most of these black shale intervals, especially OAE 2 and 1b, are characterized by low δ15N values (<0‰) commonly observed in mid-Cretaceous black shales, which seem to reflect the presence of an altered nitrogen cycle with rates of nitrogen fixation significantly higher than in the modern ocean. 1Arnaboldi, M., and Meyers, P.A., 2006. Data report: multiproxy geochemical characterization of OAErelated black shales at Site 1276, Newfoundland Basin. In Tucholke, B.E., Sibuet, J.-C., and Klaus, A. (Eds.), Proc. ODP, Sci. Results, 210: College Station, TX (Ocean Drilling Program), 1–16. doi:10.2973/odp.proc.sr.210.102.2006 2Marine Geology and Geochemistry Program, Department of Geological Sciences, The University of Michigan, 1100 North University Avenue, Ann Arbor MI 48109-1063, USA. Correspondence author: marna@umich.edu Initial receipt: 21 November 2005 Acceptance: 5 May 2006 Web publication: 21 November 2006 Ms 210SR-102 M. ARNABOLDI AND P.A. MEYERS DATA REPORT: MULTIPROXY GEOCHEMICAL CHARACTERIZATION 2