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

阿尔伯塔省的地貌特征是风积沙的堆积，这些沙在许多地方都是沙丘结构的化石。在过去的二三十年里，一种叫做发光测年的技术已经发展起来，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，作为一种破译沙子最后一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就没有保持固定。相反，在过去的10000年里，沙子在不同的时间被重新移动。这些重新激活的事件与气候变化有关。相比之下，只有数量有限的研究已经进行了沙丘序列从中央阿尔伯塔和获得的结果表明，在该地区的沙丘结构的年龄范围在15 700和10 500年之前。然而，迄今为止还没有任何研究限制了阿尔伯塔中部任何一个地点发生风沉积的持续时间，因此仍然不知道风的激活何时开始，何时结束或是否经常发生。这项研究将从中部和北方阿尔伯塔沙丘结构中收集样本，这些沙丘结构中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。将使用发光测年技术对收集的样品进行测年，以提供沉积年代。研究结果将与阿尔伯塔南部以及加拿大大草原的数据进行比较，以阐明过去20000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纳入背景。此外，沉积物从沙丘结构的较低部分应提供年龄限制冰盖从加拿大西部的最后一次冰期结束时撤出。因此，这样的年龄将被用来解决一个长期存在的问题，即在大约14000年前或更早的时候，加拿大西部是否存在一个内陆的“无冰走廊”，第一批美国人将使用它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.