A Preliminary Study on the Cold-Seep Carbonates of the Maanshan Formation, Hengchun Peninsula, Taiwan

This study examined the origin of distinctive carbonate-cemented rocks observed in borehole core BH-6, drilled at Dingtanzi, Hengchun Peninsula, southern Taiwan. We focused on the underlying strata of reefal limestone which could be divided into mudstone and conglomerate lithofacies in ascending order. The former belongs to the Maanshan Formation, which mainly consists of unconsolidated mudstone and irregular carbonate-cemented mudstone nodules. The conglomerate lithofacies mainly consists of well-rounded granule- to cobble-sized lithic grains and shows a matrix-to clast-supported fabric. The lithology of those lithoclasts mainly comprises carbonate-cemented mudstone and well-lithified calcareous sandstone, and is thought to be eroded from carbonate-cemented mudstone of the Maanshan Formation. The facies change from the underlying mudstone upward into conglomerate is abrupt, suggesting results of bottom scouring. In total, eight and 12 mudstone subsamples were respectively prepared from rocks of the mudstone