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

特别是近50年来，牙形刺已被用作地质年龄的主要生物指标。对观察到的分布的古生态学解释很大程度上归因于牙形石动物的生活习惯，只笼统地提到了死后死亡组合被破坏的可能性。通过室内沉降和水槽实验，研究了浅海碳酸盐环境中死后输运过程对牙形石元素分布的影响。由于这些磷酸盐颗粒的大小和形状变化很大，因此静态流体中的最终沉降速度存在显著差异，并建议：(1)开始运动的临界条件（平均流速），(2)在迁移的小河床内运输，(3)沿着运输路径的元素分选差异，(4)流体输送过程中的破碎量。这些流体动力学差异是极其重要的，因为它们会强烈影响离散牙形石元素的分布，特别是在中高能量状态下。这些因素的量化可用于约束潮外碳酸盐岩中保存的牙形刺组合的古生态学解释。这将允许一种定量的方法来确定牙形石元素在埋葬之前经历的死后运输的数量，并且当埋葬效应被考虑在内时，也将允许对不同样品的组成进行直接的统计比较。通过为解释在化石矿床形成过程中起主要作用的物理环境过程提供模型，对牙形刺的生物地层学和古环境数据进行量化，广泛增强了对牙形刺的生物地层学和古环境数据的解释，并对其他骨骼异体的研究产生了影响。

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.