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

艾伯塔省的景观以风沉积沙子的堆积为特色，这些沙子作为化石沙丘结构出现在许多地方。在过去的二三十年里，一种名为发光测年的技术已经开发出来，通过这种技术，来自这种地貌的沙粒可以在实验室环境中发光，作为一种手段来破译自沙子最后一次被埋藏以来已经过去的时间。使用这种方法对阿尔伯塔省南部的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不是固定的。相反，在过去的一万年里，沙子在不同的时期发生了再流动。这些重新激活的事件与气候变化有关。相比之下，仅对阿尔伯塔省中部的沙丘序列进行了有限数量的研究，结果表明，该地区的沙丘结构在距今15700年到10500年之间。然而，到目前为止，还没有研究限制艾伯塔省中部任何一个地点发生风沉积的持续时间，因此仍然不知道风激活的确切时间是什么时候开始的，什么时候结束的，或者它是否是反复发生的。这项研究将从艾伯塔省中部和北部的沙丘结构中收集样品，其中包含的沉积序列比该地区迄今所调查的任何样品都要长。收集的样品将使用发光测年技术进行测年，以提供沉积年代学。结果将与阿尔伯塔省南部以及整个加拿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理解当前全球变暖的辩论背景。此外，来自沙丘结构下部的沉积物应该为上一次冰期结束时加拿大西部冰盖的撤退提供年龄限制。因此，这些年代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一条内陆的无冰走廊，第一批美国人曾利用这条走廊向南迁移到中纬度地区。

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.