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Data report: dolomite in Neogene sediments of the Belgica carbonate mound province, Porcupine Seabight, North Atlantic1

Jay M. Gregg2 and Tracy D. Frank3


Dolomite was observed, using petrography, X-ray diffraction (XRD), and scanning electron microscopy (SEM), in cored Neogene sediments from the Porcupine Seabight in the north Atlantic Ocean, Integrated Ocean Drilling Program Expedition 307 Sites U1316, U1317, and U1318, ~100 km off the west coast of Ireland. Trace amounts (<10% of total carbonate component) of dolomite were observed in Challenger Mound, a deep coldwater mixed silicaclastic-carbonate mud mound located in the Porcupine Seabight. Significant dolomitization (>50% of total carbonate component) was observed primarily in Miocene strata in submound and off-mound sediments.

Petrographic examination of smear slides indicates that dolomite is composed of micrometer- to decimicron-sized, limpid, rhombic crystals. XRD analysis indicates that the dolomite is calcium rich and poorly ordered. SEM confirms light petrographic analysis of size and morphology of dolomite crystals, and electron microprobe analysis indicates that the dolomite is ferroan and displays distinct compositional zoning. Microbes and associated microbial filamentous structures were observed associated with dolomite crystals.

Saturation indexes of carbonate minerals calculated for interstitial waters collected from the three sites are consistent with the petrographic and XRD observation of dolomite.

1 Gregg, J.M., and Frank, T.D., 2009. Data report: dolomite in Neogene sediments of the Belgica carbonate mound province, Porcupine Seabight, North Atlantic. In Ferdelman, T.G., Kano, A., Williams, T., Henriet, J.-P., and the Expedition 307 Scientists, Proc. IODP, 307: Washington, DC (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/​iodp.proc.307.207.2009

2 Boone Pickens School of Geology, Oklahoma State University, Stillwater OK 74078, USA.

3 Department of Geosciences, University of Nebraska-Lincoln, Lincoln NE 68588, USA.

Initial receipt: 21 July 2008
Acceptance: 14 April 2009
Publication: 3 July 2009
MS 307-207