EASTERN IOWA PALEOENVIRONMENTS AND CULTURAL CHANGE: INTRODUCTION AND PALEOECOLOGICAL BACKGROUND

This paper provides an overview of the results of archaeological and paleoecological research at the Gast Farm and Gast Spring alluvial fans along the western side of the Mississippi River Valley, in southeastern Iowa. Archaeological survey and test excavations were undertaken to examine the impact of changing ecological parameters on local cultural groups. Most alluvial fans in the Project area contained small surface deposits of Woodland material, but one large fan, the Gast Farm site, contained substantial Middle and Late Woodland communities, as well as buried Archaic deposits. Preliminary analyses suggest a process of nucleation from the surrounding region after the Early Woodland period. Paleoecological investigations established a record of Holocene vegetation changes, beginning with late Pleistocene spruce-larch forest, giving way to deciduous forest, followed by a period dominated by grass and chenopods. The timing of prairie establishment is uncertain, however, and the subject of future research.

本综述系统梳理了爱荷华州东南部密西西比河谷西侧加斯农场（Gast Farm）与加斯泉（Gast Spring）冲积扇的考古与古生态研究成果。本研究开展考古调查与试掘工作，旨在探究生态参数变迁对当地文化群体的影响。本研究区域内多数冲积扇仅存小型伍德兰时期（Woodland）遗存的地表堆积，但其中一处大型冲积扇——加斯农场遗址——则蕴藏着丰富的中伍德兰与晚伍德兰时期文化堆积，同时还包含埋藏的阿卡迪亚时期（Archaic）遗存。初步分析表明，早伍德兰时期之后，该区域经历了由周边区域吸纳人口、形成文化聚居核心的发展过程。古生态调查构建了全新世（Holocene）的植被变迁序列：其初始阶段为晚更新世（late Pleistocene）的云杉-落叶松林，随后演替为落叶阔叶林，之后进入以草本与藜科植物为主的阶段。不过，北美草原（prairie）的形成时间尚未明确，该主题仍有待后续研究进一步探究。