Antarctic Peninsula Exhumation and Landscape Development Investigated by Low-Temperature Detrital Thermochronometry

低温碎屑测温法研究南极半岛的发掘和景观发育

• 批准号: 1543256
• 负责人: David Shuster
• 金额: $ 36.69万
• 依托单位: Berkeley Geochronology Center
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1543256&HistoricalAwards=false
• 关键词: Antarctic; Peninsula; Exhumation; Landscape; Development

The extreme mountain topographies of alpine landscapes at mid latitudes (e.g., European Alps, Patagonia, Alaska) are thought to have formed by the erosive action of glaciers, yet our understanding of exactly when and how those topographies developed is limited. If glacial ice was responsible for forming them, then those landscapes must have developed primarily over the last 2-3 million years when ice was present at those latitudes; this timing has only recently been confirmed by observations. In contrast, the Antarctic Peninsula, which contains similarly spectacular topographic relief, is known to have hosted alpine glaciers as early as 37 million years ago, and is currently covered by ice. Thus, if caused by glacial erosion, the high relief of the peninsula should have formed much earlier than what has been observed at mid latitude sites, yet we know nearly nothing about the timing of its development. The primary benefit of this research will be to study the timing of topography development along the Antarctic Peninsula by applying state of the art chemical analyses to sediments collected offshore. This research is important because studying a high latitude site will enable comparison with sites at mid latitudes and test current hypotheses on the development of glacial landscapes in general.This project aims to apply low-temperature thermochronometry based on the (U-Th)/He system in apatite to investigate the exhumation history, the development of the present topography, and the pattern of glacial erosion in the central Antarctic Peninsula. A number of recent studies have used this approach to study the dramatic, high-relief landscapes formed by Pleistocene alpine glacial erosion in temperate latitudes: New Zealand, the Alps, British Columbia, Alaska, and Patagonia. These studies have not only revealed when these landscapes formed, but have also provided new insights into the physical mechanisms of glacial erosion. The Antarctic Peninsula is broadly akin to temperate alpine landscapes in that the dominant landforms are massive glacial troughs. However, what we know about Antarctic glacial history suggests that the timing and history of glacial erosion was most likely very different from the temperate alpine setting: The Antarctic Peninsula has been glaciated since the Eocene, and Pleistocene climate cooling is hypothesized to have suppressed, rather than enhanced, glacial erosion. Our goal is to evaluate these hypotheses by developing a direct thermochronometric record of when and how the present glacial valley relief formed. We propose to learn about the timing and process of glacial valley formation through apatite (U-Th)/He and 4He/3He measurements on glacial sediment collected near the grounding lines of major glaciers draining the Peninsula. In effect, since we cannot sample bedrock directly that is currently covered by ice, we will rely on these glaciers to do it for us.

中纬度高山景观的极端山地地形（例如，欧洲阿尔卑斯山、巴塔哥尼亚、阿拉斯加）被认为是由冰川的侵蚀作用形成的，但我们对这些地形究竟是何时以及如何形成的了解有限。 如果冰川冰是形成它们的原因，那么这些景观必须主要是在过去的200 - 300万年里，当冰出现在这些纬度时，这些景观必须主要发展;这个时间直到最近才被观测所证实。 相比之下，南极半岛拥有类似的壮观地形起伏，已知早在3700万年前就有高山冰川，目前被冰覆盖。 因此，如果是冰川侵蚀造成的，半岛的高起伏应该比在中纬度地区观察到的要早得多，但我们对它的发展时间几乎一无所知。 这项研究的主要好处是通过对近海收集的沉积物进行最先进的化学分析，研究沿着南极半岛地形发展的时间。 这项研究是重要的，因为研究一个高纬度的网站，可以比较在中纬度的网站，并测试目前的假设，冰川景观的发展，一般。本项目的目的是应用低温热年代学的基础上（U-Th）/He系统的磷灰石，以调查折返的历史，目前的地形发展，和冰川侵蚀的模式在南极半岛中部。最近的一些研究使用这种方法来研究温带地区更新世高山冰川侵蚀形成的引人注目的高浮雕景观：新西兰，阿尔卑斯山，不列颠哥伦比亚省，阿拉斯加和巴塔哥尼亚。这些研究不仅揭示了这些景观的形成时间，而且还为冰川侵蚀的物理机制提供了新的见解。南极半岛与温带高山景观大致相似，主要地形是巨大的冰川槽。然而，我们对南极冰川历史的了解表明，冰川侵蚀的时间和历史很可能与温带高山环境非常不同：南极半岛自始新世以来一直处于冰川状态，更新世气候变冷被假设为抑制而不是增强了冰川侵蚀。我们的目标是评估这些假设，开发一个直接的热时记录的时间和如何形成目前的冰川山谷救济。 我们建议通过磷灰石（U-Th）/He和4 He/3 He测量收集的主要冰川排水半岛的接地线附近的冰川沉积物了解冰川河谷形成的时间和过程。实际上，由于我们无法直接对目前被冰覆盖的基岩进行采样，我们将依靠这些冰川来为我们做这件事。