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doi:10.2204/iodp.proc.307.201.2009

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 307 was the first attempt to drill through a deepwater coral mound, Challenger Mound, in Porcupine Seabight. Sediments from on-mound Site U1317 contain abundant deep-sea corals, mostly Lopheria pertusa, and show a cyclic change of repeated darker colored and lighter colored layers at ~10 m intervals. The darker layers are less calcareous and contain better preserved corals, whereas the lighter layers are more calcareous and contain partly dissolved corals (Titschack et al., 2006). Because the mound sediments developed in the late Pliocene and early Pleistocene (e.g., Kano et al., 2007), glacial and interglacial environmental change was considered to be reflected by these cyclic lithological changes (Williams et al., 2006).

The mound sediments, especially the lighter layers, are partly lithified. Chemical analysis of the pore water predicted microbially mediated organic matter decay and carbonate mineral precipitation (Ferdelman et al., 2006). This process is responsible for transforming the unlithified mound sediments into a conical limestone body over the next several million years.

This study focuses on geochemical properties of a lithified lighter layer and provides information to understand the lithification processes.

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