Late Quaternary Environmental History of the Noatak Basin, Northwestern Alaska

阿拉斯加西北部诺阿塔克盆地的晚第四纪环境史

• 批准号: 9424279
• 负责人: Scott Elias
• 金额: $ 9.98万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-05-01 至 1998-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9424279&HistoricalAwards=false
• 关键词: Late; Quaternary; Environmental; History; Noatak

This award supports a project to investigate the late Quaternary paleoenvironmental conditions of the Noatak basin in northwestern Alaska. The Noatak basin is a broad lowland in the western Brooks Range of Alaska, drained by the west-flowing Noatak River. During the late Pleistocene, large glaciers extended down the Noatak River valley and terminated within the basin. Other glaciers that originated farther west in the DeLong Mountains flowed eastward into the basin, damming the Noatak River and forming a succession of lakes with surface areas as large as 4400 square kilometers. This project will bring together a combination of approaches, including paleoecological analyses (pollen, plant macrofossils, and insects), stratigraphy, and geomorphology, to understand the paleoenvironmental records preserved in deposits in the numerous large bluffs along the Noatak and Cutler Rivers. The research focuses on organic-rich sediments exposed in the bluffs. Basic stratigraphic and geomorphologic mapping of these bluffs has already been accomplished and test samples taken for paleoecological study in 1993 and 1994 have yielded abundant, well-preserved macrofossils (plants and insects) and pollen assemblages. This project will yield significant paleoenvironmental data that will be placed in well-constrained chronological and stratigraphic contexts. The Noatak basin contains an excellent record of the last glacial/interglacial cycle, preserved in a series of organic deposits exposed in river bluffs. Poorly drained lake beds cover the floor of the Noatak basin, and associated end moraines reflect glacial advances from mountains to the north, east, and west. During interglacial and interstadial intervals, the Noatak River and its tributaries incised these glacial deposits and glaciolacustrine complexes. They formed gravel-filled channels capped by organic-rich bog, marsh, and floodplain deposits. Sixty- two measured sections of river-bluff exposures provide a record o f depositional facies across the lake floor. The sedimentary sequences exposed in the bluffs define multiple glacial advances and corresponding lake stages separated by fluvial sediments of both interstadial and interglacial character. Peat beds and organic-rich silt horizons from floodplain deposits have yielded identifiable wood, plant macrofossils, pollen, and insect remains, and other fossils that serve as biostratigraphic markers and provide paleoecological information. Peats and organic-rich silts and sands were deposited during several key intervals throughout the last 135,000 years. The nine study sites that are part of this project include organic deposits that most likely date to the last interglacial period, the Boutellier (mid- Wisconsin) interstadial, the late Wisconsin maximum, (27,000- 17,000 years ago), the late glacial interval (13,500-10,000 years ago), and the Holocene. The study region lies within the Noatak National Preserve, one of the proposed component parks of the U.S./Russian Beringia International Park. Its position near the eastern margin of the Bering Land Bridge places it within a region where organic-rich riparian habitats prevailed during even the last glacial maximum. Paleoecological studies in the Noatak basin are essential to help decipher an unusually long and complex record of Pleistocene glaciation, modern landscape formation, and biotic response to climate change. These studies will also provide the environmental underpinning of the rich archaeological record that is presently being reconstructed in the Noatak region.

该奖项支持了一个项目，以调查晚第四纪的古环境条件的诺阿塔克盆地西北阿拉斯加。 诺阿塔克盆地（英语：Noatak basin）是阿拉斯加州西部布鲁克斯山脉的一片广阔的低地，由向西流动的诺阿塔克河（英语：Noatak River）排出。在更新世晚期，大型冰川沿着诺阿塔克河谷向下延伸，并在盆地内终止。其他冰川起源于德隆山脉以西，向东流入盆地，阻塞了诺塔克河，形成了一系列面积达4400平方公里的湖泊。该项目将汇集各种方法，包括古生态学分析（花粉、植物宏体化石和昆虫）、地层学和地貌学，以了解诺亚塔克河和卡特勒河沿着众多大悬崖沉积物中保存的古环境记录。研究重点是暴露在悬崖中的富含有机物的沉积物。这些悬崖的基本地层和地貌制图已经完成，1993年和1994年为古生态研究采集的测试样品已经产生了丰富的、保存完好的大型化石（植物和昆虫）和花粉组合。该项目将产生重要的古环境数据，这些数据将被放置在约束良好的年代和地层背景中。 诺阿塔克盆地保存了最后一次冰期/间冰期循环的极好记录，这些记录保存在河流悬崖中暴露的一系列有机沉积物中。排水不良的湖床覆盖着诺阿塔克盆地的底部，相关的末端冰碛反映了冰川从山脉向北部、东部和西部的推进。在间冰期和间冰期期间，Noatak河及其支流切割了这些冰川沉积物和冰湖复合体。它们形成了砾石充填的河道，上面覆盖着富含有机物的沼泽、沼泽和河漫滩沉积物。62个测得的河流陡崖暴露剖面提供了横跨湖底的沉积相记录。暴露在悬崖的沉积序列定义多个冰川的进步和相应的湖泊阶段分开的河流沉积物的间冰期和间冰期的性格。泥炭床和有机物丰富的淤泥层从河漫滩沉积物产生了可识别的木材，植物大化石，花粉，昆虫遗骸，以及其他化石，作为生物地层标志，并提供古生态信息。 在过去的135，000年中，泥炭和富含有机物的粉砂和沙子在几个关键时期沉积。该项目的九个研究地点包括最有可能追溯到末次间冰期的有机沉积物、布泰利埃（威斯康星州中期）间冰期、威斯康星州晚期最大期（27，000 - 17，000年前）、晚冰期（13，500 - 10，000年前）和全新世。 研究区域位于Noatak国家保护区内，Noatak国家保护区是美国拟议的组成公园之一。俄罗斯白令吉亚国际公园它的位置靠近白令陆桥的东部边缘，即使在最后一次盛冰期，它也是一个有机丰富的河岸栖息地。 诺雅塔克盆地的古生态学研究是必不可少的，有助于破译更新世冰川作用，现代景观形成和生物对气候变化的反应异常漫长而复杂的记录。这些研究还将为目前正在Noatak地区重建的丰富考古记录提供环境基础。