REVIEWS ON CHRYSANTHEMUM STONES FROM THE QIXIA FORMATION IN SOUTH CHINA

Chrysanthemum stones recognized in the Qixia Formation in South China are known as the chrysanthemum-shaped druses which consist of the radially-arranged columnar crystals. They occur usually as calcite pseudomorphs in the upper part of the Qixia Formation(Artinskian)in Liuyang of Hunan, Laibin of Guangxi and Huangshi of Hubei. Despite its different locaties, the following similarities may be seen.(1)They occur almost in the same horizon in the Qixia Formation and have only been confined to the formation so far;(2)They are identical in form and dimensions;(3)They are composed dominantly of calcite, with small amounts of chalcedony. Calcite generally shows generation structure and chalcedony occurs as the filling material in the voids. Although the mineral celestite has been observed in some samples from Liuyang in Hunan, it seems that the celestite is the product resulted from replacement during diagenesis rather than a kind of original mineral, and (4)they commonly enclose micro-fossils and pierce the bedding plane. The chrysanthemum stones in the study area were interpreted as celestite or celestite pseudomorphs by the previous workers. The author contend, however, that they should be pseodumouphs after ikaite. This explanation is strongly supported by the geological settings during the Qixiaian including cold climates and cold upwelling currents and by sedimentary characteristics of the Qixia Formation such as the presence of foramol skeletal grain assemblages and the absence of non-skeletal grains and organic reefs. It Is concluded that the chrysanthemum stones from the study area may be pseudomorphs after ikaite and the Qixia Formation might have resulted from cool- to cold-water deposition.