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doi:10.2204/iodp.proc.307.207.2009

Introduction

Challenger Mound (Belgica carbonate mound province) is located ~100 km off the southwest coast of County Kerry, Ireland, in water depths between 550 and 1025 m (Figs. F1, F2). Miocene sediments in the region are composed of mixed siliciclastics (silts and clays) and carbonates (nannoplankton and coldwater metazoan skeletal debris). These sediments are overlain by Pliocene to Pleistocene coldwater coral carbonate mud mounds and their laterally equivalent sediments. The mounds are analogous in their large-scale geometry and position on the shelf margin to fossil carbonate mud mounds common in Paleozoic strata (Lees and Miller, 1995). However, the Neogene mounds are dissimilar to Paleozoic carbonate mounds in that they are composed of coldwater coral in a matrix of mixed siliciclastic and carbonate sediments. They also lack stromatactis structures or any evidence of submarine carbonate cementation as is common in Paleozoic carbonate mounds (De Mol et al., 2002; Henriet et al., 2005; Gregg et al., 2006).

The primary purpose of Integrated Ocean Drilling Program (IODP) Expedition 307 was to investigate the origin and evolution of the deep, coldwater carbonate mounds. Coring was conducted on and adjacent to Challenger Mound (Fig. F2). The “Expedition 307 summary” chapter and Kano et al. (2007) discuss the stratigraphy and sedimentary facies of the cored sediments. This data report documents the observation of trace diagenetic dolomite within the mud mound sediments and trace to significant dolomite in submound and off-mound sediments. This report also characterizes the dolomite petrographically as well as compositionally and documents the association of microorganisms with some occurrences of significant authigenic dolomite.

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