Insect Fossils and Late Quaternary Environments of South- Western Alaska

阿拉斯加西南部晚第四纪的古环境研究很少，该地区过去的环境变化与白令陆桥内陆地区的环境变化之间的关系尚不完全清楚。对Nushagak、Holitna和Upper Kuskokwin低地晚第四纪沉积物中昆虫化石和花粉组合的分析，为这个以前被忽视的白令陆桥避难所提供了重要的新信息。在晚更新世期间，阿拉斯加西南部比内陆地区湿润的环境显然一直存在，这一地区可能为那些无法在大陆地区生存的昆虫提供了避难环境。低温昆虫分类群的化石组合也提供了一种限制阿拉斯加这部分地区过去夏季温度的手段，有助于我们了解整个白令陆桥的气候条件。该研究项目的优势之一是对阿拉斯加西南部地区的多个地点进行分析，从而更清楚地了解区域古环境信号和当地变化的程度。这些古昆虫学和孢粉学研究将为阿拉斯加西南部提供一个更完整的晚第四纪古环境记录，重点是(1)从末冰期到全新世气候的过渡；(2)以前只在东白令陆桥内陆地区发现的威斯康星中部温暖间隔的可能性。研究结果将有助于确定整个白令陆桥次大陆的晚第四纪气候和环境梯度，并有助于理解这个晚更新世避难所的生态动态。

Late-Quaternary paleoenvironments of southwestern Alaska have received little study, and the relationship of past environmental changes in this region to those in more-interior regions of Beringia is not yet completely understood. Analyses of fossil insect and pollen assemblages from late-Quaternary sediments of the Nushagak, Holitna, and Upper Kuskokwin lowlands have yielded significant new information on this previously neglected region of the Beringian refugium. Conditions somewhat more humid than those at interior sites apparently persisted in southwestern Alaska during the late-Pleistocene, and this region may have provided refugial environments for insects that could not survive at more-continental localities. Fossil assemblages of stenothermic insect taxa also provide a means of constraining past summer temperatures in this portion of Alaska, contributing to our knowledge of climatic conditions in Beringia as a whole. One of the strengths of the research project is the analysis of multiple sites from the southwestern Alaska region, allowing a clearer picture of the regional paleoenvironmental signal and the degree of local variability. These paleoentomological and palynological studies will provide a more complete late-Quaternary paleoenvironmental record for southwestern Alaska, with emphasis on (1) the transition from last-glacial to Holocene climates and (2) the possibility of a Middle Wisconsinan warm interval previously recognized only in interior regions of eastern Beringia. The results of the study will contribute substantially toward the determination of late-Quaternary climatic and environmental gradients across the Beringian subcontinent and toward an understanding of the ecological dynamics of this late-Pleistocene refugium.