COLLABORATIVE RESEARCH: Time-Averaging in Mixed Brachiopod- Mollusk Assemblages along a Depth Gradient across a Modern Tropical Shelf

时间平均过程对时间分辨率的限制（即，化石的年龄混合决定了化石记录的时间分辨率）对于在各种类型的研究中解释化石记录具有广泛的意义。 腕足动物是古生代和许多晚期海相贝壳组合的主要生物，目前几乎没有关于腕足动物时间平均的资料。 我们建议使用氨基酸消旋和放射性碳测年的组合来记录时间平均的混合腕足类软体动物壳在巴西南部大陆架的surfaluminium积累。 由此产生的数据将提供定量估计的年龄结构的腕足动物和软体动物从七个网站沿着的深度梯度。预计这项研究将产生（1）对腕足动物壳积累的时间平均的第一次定量估计，（2）对两组生物矿化生物（腕足动物与软体动物）的时间平均的第一次比较数据，（3）对沿海岸-近海水深梯度的时间平均沿着的第一次估计。通过将分类学和环境维度添加到当前的时间平均知识中，这项研究将为我们理解化石记录的时间分辨率做出重大贡献。

The limits to temporal resolution imposed by processes of time-averaging (i.e., age mixing of fossils that determines the temporal resolution of the fossil record) have broad implications for interpretation of the fossil record in a wide variety of types of studies. Almost no information on time-averaging is currently available for brachiopods, the predominant organism comprising Paleozoic and many later marine shell assemblages. We propose to use a combination of amino acid racemization and radiocarbon dating to document time-averaging in surficial accumulations of mixed brachiopod-mollusk shells on the southern Brazilian shelf. The resulting data will provide quantitative estimates of age structures of dated shells of brachiopods and mollusks from seven sites along a depth gradient. The study is expected to produce (1) the first quantitative estimates of time-averaging for brachiopod shell accumulations, (2) the first comparative data on time-averaging for two groups of biomineralized organisms (brachiopods vs. mollusks), and (3) the first estimates of time-averaging along an onshore-offshore bathymetric gradient. By adding taxonomic and environmental dimensions to the current knowledge of time-averaging, this study will provide a significant contribution to our understanding of the temporal resolution of the fossil record.