Late Wisconsinan and holocene depositional chronologies of aeolian sands in central and northern Alberta: implications for deglaciation patterns and environmental evolution

艾伯塔省中部和北部威斯康星州晚期和全新世风沙沉积年表：对冰消模式和环境演化的影响

• 批准号: 342892-2008
• 负责人: Munyikwa, Kennedy
• 金额: $ 1.09万
• 依托单位: Athabasca University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2012
• 资助国家: 加拿大
• 起止时间: 2012-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=496993
• 关键词: Late; Wisconsinan; holocene; depositional; chronologies

The landscape of the province of Alberta features accumulations of wind deposited sands that occur in many places as fossil dune structures. Over the last two to three decades, a technique called luminescence dating has been developed by which sand grains from such landforms can be made to glow in a laboratory setting as a means of deciphering the amount of time that has elapsed since the sands were last buried. Investigations performed on dune structures from southern Alberta using such methods have demonstrated that the dune structures there have not remained fixed since their first emplacement. Instead, the sands have been remobilized at various times over the last 10 000 years. These episodes of reactivation have been linked to variations in climate. Contrastingly, only a limited number of studies have been carried out on dune sequences from central Alberta and results obtained suggest the dune structures in the region range in age between 15 700 and 10 500 years before present. No study to date, however, has constrained the duration over which deposition by wind occurred at any one location in central Alberta such that it remains unknown when precisely the activation by wind began, when it ended or whether it was recurrent. This study will collect samples from dune structures in central and northern Alberta containing depositional sequences longer than any investigated in the area to date. The collected samples will be dated using luminescence dating techniques to provide depositional chronologies. The results will be compared with data from southern Alberta as well those from across the Canadian prairies to elucidate on patterns in environmental change over the last 20 000 years. Such medium range data on climate change will help put the current global warming debate into context. In addition, sediments from lower sections of the dune structures should provide age constraints for the withdrawal of ice sheets from western Canada at the end of the last glacial period. Hence, such ages will be used to address the long standing question of whether an inland 'ice-free corridor' did exist in western Canada around about 14 000 years ago or earlier that would have been used by the first Americans to migrate south to the mid latitudes.

阿尔伯塔省的景观特点是风沉积的沙子在许多地方形成化石沙丘结构。在过去的二三十年里，一种被称为发光测年的技术已经被开发出来，通过这种技术，可以使来自这种地貌的沙粒在实验室环境中发光，作为一种破译沙子上次被掩埋以来已经过去的时间的手段。使用这种方法对阿尔伯塔省南部沙丘结构进行的调查表明，那里的沙丘结构自第一次就位以来并没有保持固定。相反，在过去的一万年里，这些沙子在不同的时间被重新利用。这些重新激活的事件与气候变化有关。相比之下，对阿尔伯塔中部沙丘序列的研究数量有限，结果表明该地区沙丘结构的年龄在15 700年至10 500年之间。然而，到目前为止，还没有研究限制了阿尔伯塔中部任何一个地方的风沉积持续的时间，以至于我们仍然不知道风的激活确切地是什么时候开始的，什么时候结束的，或者它是否反复发生。这项研究将从阿尔伯塔省中部和北部的沙丘结构中收集样本，其中包含的沉积序列比迄今为止在该地区调查的任何沉积序列都要长。收集到的样品将使用发光测年技术来确定年代，以提供沉积年表。这些结果将与阿尔伯塔省南部以及加拿大大草原的数据进行比较，以阐明过去2万年来环境变化的模式。这些关于气候变化的中期数据将有助于将当前的全球变暖辩论置于背景中。此外，沙丘结构下部的沉积物应该为末次冰期结束时冰盖从加拿大西部撤出提供年龄限制。因此，这样的年龄将被用来解决一个长期存在的问题，即大约14000年前或更早的时候，加拿大西部是否存在内陆“无冰走廊”，第一批美国人可能利用这条走廊向南迁移到中纬度地区。