Collaborative Research: Recovery of Vertebrate Faunas after the K/T Boundary, Tullock Formation, Eastern Montana

该项目的第一个目标将是完善蒙大拿州东部已经发现和采样的100多个早古新世脊椎动物化石地点的地层相关性。这里广泛分布的煤/褐煤层包裹着许多化石位置，含有含硅膨润土的互层，非常适合40Ar/39Ar测年，潜在分辨率为0.1%。使用Swisher等人（1993）描述的标准进行的初步研究表明，高分辨率的40Ar/39Ar年龄测定，结合对互层火山的显微探针分析和详细的磁地层学，能够为整个地区的单个煤/褐煤床提供精确的识别。由此得出的年表将为检验蒙大拿州早古新世当地动物群与新墨西哥、阿尔伯塔和中间地区已知动物群的相关性假设提供基础。对大规模灭绝后生物恢复的过程和速度的解释涉及到关于当地生存、枝源多样化和来自避难地区的移民的相对重要性的相互矛盾的假设。初步结果表明，在蒙大拿州东部发现的早古新世，北美洲陆地哺乳动物时代（narma）持续时间约为1 Ma。普尔坎和早托雷乔尼期纳尔玛（中古新世）地区动物群至少可以划分为4个时间单位。对这些地层学控制良好的当地动物群中哺乳动物和其他脊椎动物的系统关系的分析，将为对白垩纪大灭绝后陆地生物群恢复过程中起作用的进化过程的假设进行更精确的检验提供基础。局部和系统的数据将继续记录在加利福尼亚大学古生物学博物馆基于计算机的管理系统中，并将随时提供给研究界。

Clemens 9505841 The first objective of the project will be to refine the stratigraphic correlations of over 100 Early Paleocene vertebrate fossil localities in eastern Montana already discovered and sampled. Here widespread coal/lignite beds bracketing many fossil localities contain interbeds of sanidine-bearing bentonites excellent for 40Ar/39Ar dating with a potential resolution of 0.1%. Preliminary studies using criteria described by Swisher et al. (1993) indicate that high resolution 40Ar/39Ar age determinations, in conjunction with microprobe analysis of interbedded volcanics and detailed magnetostratigraphies, are capable of providing precise identifications of individual coal/lignite beds throughout the area. The resulting chronology will provide the basis for testing hypotheses of correlation of Early Paleocene local faunas from Montana with those known from New Mexico, Alberta, and intervening areas. Interpretations of the processes and rates of biotic recovery after mass extinctions involve competing hypotheses concerning the relative significance of local survival, cladogenic diversification, and immigration from refuge areas. Our preliminary results show the Early Paleocene, Puercan North American Land Mammal Age (NALMA), as recognized in eastern Montana, had a duration of ca. 1 Ma. Puercan and early Torrejonian NALMA (Middle Paleocene) local faunas can be ordered in at least four temporal units. Analysis of the systematic relationships of the mammals and other vertebrates in these stratigraphically well-controlled local faunas will provide the basis for much more refined tests of hypotheses concerning the evolutionary processes operative during the recovery of the terrestrial biota after the Cretaceous mass extinction than previously possible. Locality and systematic data will continue to be recorded in computer-based curatorial systems at the University of California Museum of Paleontology and will be readily available to the research community.