漂游类化石居群的死亡曲线及其意义

DEAD CURVE OF THE PELAGIC FORMS AND THEIR PALEOECOLOGICAL SIGNIFICANCE

论述了漂游类化石居群死亡曲线的模型、绘制方法、曲线形状以及在古生态学研究中的意义。假定所研究的化石居群中的所有个体是同时(期)死亡的,这对于在同一层面或同一薄层中保存完整的原地埋藏或仅仅经过短距离搬运的居群来说是成立的,根据化石门类的自身特点及研究目的来确定年令间隔。如对于单笔石科的Okiavites spiralis来说,选其笔石枝旋转的圈数作为年令间隔,并把这个间隔作横坐标值;选择同一层面上单位面积中的化石数的对数值作纵坐标值,其基数为50或100。绘制死亡曲线。死亡曲线有右纠凸形、对角线形和左斜凹形3种形状。本文根据保存于不同岩层中的同一种笔石的死亡曲线变化,讨论了笔石生活环境的变化以及这种变化与笔石死亡率的关系。

The model, method of the drawing and the kinds of the dead curves of the pelagic forms and their paleoecologioal significance are studied. First, supposing the individuals in one species population that preserved in same bedding plane were dead at same time.Then choosing the length or the number of the circle of the fossils that based on the characteristics of the genus or the species as the age interval which is the abscissa axis.The ordinate axis is the iogarithms of the number of the fossils, the radix number is 50 or 100 and then drawing the curves. The dead curves have three shapes: right side convex,diagonal line and left side concave.Based on the alteration of the dead curve shapes of one species of graptolites that preserved in defferent beds, this paper disseusses the alteration of the environment and its influence to the deathrate of graptolites.