Biochronology and Evolution of Early and Middle Paleocene Nonmarine Mollusca of the Northern Great Plains

非海洋软体动物是世界上最丰富的动物宏体化石。 北美西部古新世大陆地层。 他们的 然而，生物年代学的潜力尚未实现，主要是由于 对缺乏研究集中在确定 在厚层序中的生物地层范围 在时间上受哺乳动物化石的影响。 本研究 将完成Puercan和Torrejonian的生物地层分区 Crazy Mountains盆地的地层（古新世早期和中期）， 蒙大拿州的软体动物和哺乳动物的数量 尤其是众多。 这种分带将在生物年代学上 与该地区类似年龄的软体动物和哺乳动物地层相关 蒙大拿州的派克堡地区，以及蒙大拿州的柏树山和大泥泞地区。 萨斯喀彻温省。 Puercan，Torrejonian和早期Tiffanian年龄层 复合部分将在时间上与丰富的 小密苏里州的含油气的蒂法阶（古新世晚期）地层 北达科他州西南部的一段河流。 综合部分将 提供了第一个全面的非海洋软体动物生物年代学， 北美古新世，并将专门作为参考 大平原北方的软体动物和哺乳动物区。

Nonmarine Mollusca are the most abundant animal macrofossil of Paleocene continental strata in western North America. Their biochronologic potential, however, has yet to be realized due primarily to the lack of study focused on the determination of the biostratigraphic ranges of taxa in thick sequences of strata temporally-controlled by correlation with fossil mammals. This study will complete a biostratigraphic zonation of Puercan and Torrejonian Strata (early and middle Paleocene) in the Crazy Mountains Basin, Montana where the number of molluscan and mammalian localities are particularly numerous. This zonation will be biochronologically correlated with mollusk-and mammal-bearing strata of similar age in the Fort Peck area of Montana, and the Cypress Hills and Big Muddy areas of Saskatchewan. The Puercan, Torrejonian, and early Tiffanian age strata composite section will be temporally overlapped with the richly fossiliferous Tiffanian (upper Paleocene) strata of the Little Missouri River section in southwestern North Dakota. The composite section will provide the first overall nonmarine molluscan biochronology for the Paleocene of North America, and will specifically serve as a reference section for both mollusks and mammals in the northern Great Plains.