COLLABORATIVE RESEARCH: On Middle Miocene Biogeography and Biostratigraphy in the Northern Rocky Mountains of Idaho, Montana, and Wyoming

该项目继续研究中中新世构造作用对落基山脉北部哺乳动物生物地理格局的影响。该项目将测试有关爱达荷州、蒙大拿州和怀俄明州中第三系不整合的形态模式、生物地理模式和发展之间的一致性的假设。这项研究将集中于解释来自5个山间盆地巴斯多夫沉积的类地肌类啮齿动物(地鼠、袋鼠等)的地质年代学和生物地理模式。地肌样啮齿动物是焦点，因为它们在不整合形成后刚刚经历了明显的辐射。将使用计算机成像和地理信息系统技术，结合分支学方法，分析每个盆地准确测年层位中丰富的地球肌状牙齿遗骸的生物地理意义，以及来自大平原和大盆地其他地方的适当比较材料。这项研究在以下方面引起了广泛的兴趣：(1)确定地质和生物过程之间在时间尺度上的相互作用，但很少有人注意到这一点(200-300万年)；(2)应用新的古生物学技术(成像和地理信息系统)，使我们能够解决古生物学家(演化、物种形成)和地质学家(盆地形成年代学)感兴趣的问题；(3)完善中中新世中新世磁性地层、脊椎动物生物年代学和辐射时间尺度的联系，这对于理解落基山脉北部的构造演化至关重要。

This project continues work on the effect of middle Miocene tectonism on mammalian biogeographic patterns in the northern Rocky Mountains. The project will test hypotheses concerning the concordance between morphologic patterns, biogeographic patterns and development of the Mid-Tertiary unconformity in Idaho, Montana, and Wyoming. The study will focus on interpreting the geochronologic and biogeographic patterns of the geomyoid rodents (gophers, kangaroo rats, and such) from Barstovian deposits in 5 intermontane basins. Geomyoid rodents are the focus because they underwent a pronounced radiation just after the unconformity developed. Computerized imaging and Geographic Information System techniques, combined with a cladistic approach, will be used to analyze the biogeographic meaning of the abundant geomyoid dental remains from well-dated horizons in each of the basins, as well as appropriate comparative material from other localities in the Great Plains and Great Basin. The research is of widespread interest in (1) identifying the interplay between geologic and biotic processes on a timescale that has received little attention (2-3 million years); (2) applying new paleontological techniques (imaging and GIS) that allow us to address problems of interest to both paleontologists (evolution, speciation) and geologists (chronology of basin formation) and (3) refining links of the magnetostratigraphic, vertebrate biochronologic, and radiometric time scales in the middle Miocene, which is critical for understanding the tectonic evolution of the northern Rockies.