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几乎没有得到研究，该地区过去的环境变化与贝林贾更内陆地区的环境变化之间的关系还没有完全弄清楚。对努沙加克、霍利特纳和上库斯科温低地晚第四纪沉积中的昆虫和花粉化石组合的分析，在这个以前被忽视的柏林纪避难所地区获得了重要的新信息。在晚更新世，阿拉斯加西南部的环境显然比内陆地区更潮湿，这一地区可能为无法在更多大陆地区生存的昆虫提供了避难环境。狭窄昆虫分类群的化石组合也提供了一种限制阿拉斯加这一地区过去夏季气温的手段，有助于我们对贝林贾作为一个整体的气候条件的了解。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了分析，从而可以更清楚地了解该地区的古环境信号和当地的可变性程度。这些古昆虫学和孢粉学研究将提供阿拉斯加西南部晚第四纪的更完整的古环境记录，重点是(1)从末次冰期气候向全新世气候的过渡和(2)以前仅在贝林贾东部内陆地区认识到的中威斯康星州暖期的可能性。研究结果将有助于确定柏林次大陆晚第四纪的气候和环境梯度，并有助于理解这一晚更新世避难所的生态动力学。

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.