Fades of Devonian fore reef limestones: a quantitative study (Iberg Reef, Harz Mts., Germany)

摘要

Facies in a 238-m-long core drilled through the fore reef of the Devonian (Givetian-Frasnian) Iberg Reef is largely characterised by detrital deposits. Fibrous, early marine cements are common. Stromatoporoids, corals, and crinoids are the dominant reef-building taxa. Brachiopods, cephalopods, and conodontophorids belong to the reef dwellers. Reef destroyers include gastropods and rare echi-noids. Quantitative analysis of abundance data allows for dilineation of five facies including detritus-rich grainstones-rudstones, cement- and detritus-rich grainstones-radstones, cement-rich rudstones, stromatoporoid rudstones, and cri-noid grainstones. Time-series analysis indicates cyclic sedimentation that might have been related to mid-late Devonian third-order sea-level variations. However, the long-term (mid-Devonian to Early Carboniferous) development of the Iberg Reef including the post-reef seamount stage was presumably controlled by subsidence.