Facies 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 echinoids. Quantitative analysis of abundance data allows for dilineation of five facies including detritus-rich grainstones–rudstones, cement- and detritus-rich grainstones–rudstones, cement-rich rudstones, stromatoporoid rudstones, and crinoid 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.