第四纪石笋剖面的初步建立——以北京石花洞为例

Primary Establishment of Quaternary Stalagmite Section in the Shihua Cave,Beijing

北京石花洞位于房山花岗岩体边缘向形带的东北扬起端,与北京猿人遗址南北相望,地层均为奥陶系马家沟组石灰岩。洞内石笋记录了中更新世以来北京西山古环境的变化,可以建立第四纪石笋剖面。钙板的铀系年龄为334.99～366.74 ka,定名钙板组(Qp2g)。粗犷石笋的铀系年龄为169～235 ka,粗犷石笋的电子自旋共振年龄为130～518 ka,属中更新世沉积,定名云水洞组(Qp2y)。杆状石笋的铀系年龄为14.9±2.1～100.3±11.1 ka,属晚更新世沉积,定名石花洞组(Qp3sh)。在全新世石笋中,微层与微层之间存在厚约1μm的条带状纹线,是划分微层层数的标志,具有微层理的石笋14C年龄为0.58～2.50 ka,定名守备支洞组(Qhsh)。

Beijing Shihua Cave sits at the northeastern of granite fringe synclial belt in Fangshan, and is face to face with Peking Man （Homo erectus pekinensis ）Site. Their layer is limestone in Ordovician Period. Among Chinese Karst caves, Beijing Shihua Cave has got the most complete sorts of speleothems. There is the superimposed relationship of stalagmite from drip water is evident and the microbanding of stalagmite grows clear in Holocene. The speleothems recorded the changing information of Beijing Western Hills antique environment since Middle Pleistocene, which could set up Quaternary section of stalagmite. The U dating of calcareous plate is 334.99 - 366.74 ka, ,named Gaiban Fm. The U dating of wide stalagmite is 169 - 235 ka, and the ESR dating of wide stalagmite is 130 - 518 ka, all of which were deposited in Middle Pleistocene, named Yunshuidong Fro. The U dating of rod-like stalagmite is 14.9±2.1 - 100.3± 11. I ka, which was deposited in Upper Pleistocene, named Shihua- dong Fro. In Holocene stalagmite, usually there is an about 1 μm-thick dark stripe deposited between two microbandings, which in fact is the boundary of two microbandings. It is a mark of microbanding quantities. 14C dating of microbanding stalagmite is 0.58 - 2.50 ka, named Shoubeizhidong Fm.