【摘要】 <正> 本文主要讨论龙头山礁的岩石类型,主要造礁生物及生态,生物礁的微相和发育演化。在此基础上提出龙头山礁的沉积模式和控制因素。更多还原

【Abstract】 The Devonian Longtoushan organic reef in Dachang developed in a Hercynian back-arc extensional down-faulted basin of South China during transgression. Under the control of the wind from the southwest the organic reef body formed an asymmetric horse-shoe reef with a steep western flank and a gentle eastern flank. The barrier-frame-type reef core occurs in the form of crest on the windward western flank, while the eastern lee flank was a gentle back-reef flat zone. The reef-building organisms consist mainly of stromatoporoids and tabulates with various ecologic type. The reephilic organisms include echinoderms, brachiopods and bivalves. Reef limestones may be divided into two major categories, autochthonous biolithite and allochthonous bioclastic limestone; the former constitutes the reef core and the latter forms the rest of the reef complex. The growth of the reef began in the late Tangding time and ended in the early Luofuian time. The reef is an overlapping reef with five growing cycles,and each cycle represents a sequence shallowing from bank upwards to reef. The thickness of the entire reef complex is more than 850 m. The tectonism, main wind and wave direction, climatic conditions and submarine topography are leading factors controlling the development of the organic reef.更多还原