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The carbonate platform of Tithonian-?Berriasian age encountered on the western flank of the Galicia Bank at Site 639 is part of an extensive Late Jurassic carbonate shelf extending from Algarve to the Lusitanian Basin, Galicia Bank, and eastern Grand Banks of Newfoundland. The platform, which locally could be up to 400 m thick, probably overlies older sedimentary or low-grade metamorphic strata at Site 639. The 287 m of carbonates penetrated at this site was deposited mainly in shelf lagoon and shelf edge shoals, with localized low-relief biohermal mounds, in response to eustatic sea-level fluctuations and regional subsidence during the Tithonian-Berriasian. Minor block faulting influenced lithofacies distribution at the shelf edge. Shallow burial cementation was the most significant diagenetic event. After burial by several hundred meters of younger sediments, the top of the carbonate platform underwent extensive dolomitization during a period of tectonic fragmentation, followed by subaerial exposure and erosion of the platform. Such processes resulted in a complex carbonate diagenetic history with several periods of dolomitization. The major dolomitization event is the result of the replacement or mixing of formation fluids with evaporitic brines in a shallow subsurface setting. The emerged carbonate platform drowned during the middle early Valanginian as a result of eustatic sea-level rise and tectonic subsidence and was covered by Valanginian turbidites. During a second, more intensive period of tectonic deformation, probably in the late Valanginian, the development of large rotational faults resulted in tilting of the carbonate platform blocks toward the east. After tilting, the outer margin rapidly subsided to abyssal depths during the Late Cretaceous-early Tertiary. The development of the carbonate platform helps in dating the major tensional episodes on the western flank of Galicia Bank as late Berriasian-earliest Valanginian and ?late Valanginian in age.

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This informal report was prepared from the shipboard files by the scientists who participated in the cruise. The report was assembled under time constraints and is not considered to be a formal publication which incorporates final works or conclusions of the participating scientists. The material contained herein is privileged proprietary information and cannot be used for publication or quotation.