Experimental Models for Hydrodynamic Transport of Conodonts (Chordata) in Shallow Marine Environments

牙形刺被用作地质年代的主要生物学指标，特别是在最近50年。对观察到的分布的古生态解释在很大程度上归因于牙形刺动物的生活习性，只是笼统地提到了死亡组合死后破坏的可能性。将通过实验室沉降法和水槽实验研究浅海碳酸盐环境中死后迁移过程对牙形刺元素分布的影响。由于这些磷酸盐颗粒的大小和形状变化很大，静态流体中的最终沉降速度存在显著差异，并被认为是(1)启动运动的临界条件(平均流速)，(2)在迁移的小床面内的传输，(3)沿传输路径的元素的不同分选，以及(4)流体传输过程中的破碎量。这些水动力差异是极其重要的，因为它们将强烈影响离散牙形刺元素的分布，特别是在中到高能量区域。这些因素的量化可以用来约束潮周碳酸盐岩中保存下来的牙形刺组合的古生态解释。这将允许一种定量的方法来确定牙形刺元素在埋葬前所经历的死后运输量，还将允许对不同样品的组成进行直接统计比较，当考虑到Taphonomic效应时。身体迁移的量化广泛地加强了牙形刺的生物地层学和古环境数据的解释，并对其他骨骼异物的研究产生了影响，为解释在化石沉积形成中发挥主要作用的物理环境过程提供了模型。

Conodonts have been utilized, especially during the last 50 years, as principal biologic indices of geologic age. Paleoecologic interpretations of observed distributions have been attributed largely to life habits of conodont animals, and only general mention has been made of the potential for post-mortem disruption of death assemblages. The effects of post-mortem transport processes on distributions of conodont elements in shallow-marine carbonate environments will be investigated by means of laboratory settling and flume experiments. Because of the highly variable sizes and shapes of these phosphatic grains, significant differences exist in terminal settling velocity in a static fluid and are suggested for (1) critical conditions (mean flow velocity) for initiation of movement, (2) transport within migrating small bedforms, (3) differential sorting of elements along a transport path, and (4) amount of breakage during fluid transport. These hydrodynamic differences are extremely important because they would have strongly influenced the distribution of discrete conodont elements, particularly in moderate to high energy regimes. Quantification of these factors can then be used to constrain the paleoecologic interpretation of preserved assemblages of conodonts in peritidal carbonate rocks. This will permit a quantitative approach to determining the amount of post-mortem transport experienced by conodont elements prior to their burial and will also allow for direct statistical comparison of the composition of different samples, when taphonomic effects are factored. Quantification of post-mortem transport broadly enhances the interpretation of biostratigraphic and paleoenvironmental data of conodonts, with implications for the study of other skeletal allochems, by providing models for the interpretation of physical environmental processes that played a major role in the formation of fossiliferous deposits.