The cause of major lake level changes during the evolution of Lake Van (Anatolia): internal (tectonic-volcanic) vs. external (climate) forcing

凡湖（安纳托利亚）演化过程中主要湖水位变化的原因：内部（构造火山）与外部（气候）强迫

• 批准号: 414840187
• 负责人: Professor Dr. Hans-Ulrich Schmincke
• 金额: --
• 依托单位: Forschungseinheit Magmatische und Hydrothermale Systeme
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/414840187?language=en
• 关键词: cause; major; lake; level; changes

The origin of major lake level changes during the evolution of the ca. 600 ka old (ca. 220 m drilled sediments including ca. 25% (up to ca. 500) primary and reworked tephras) fault-bound Lake Van (Anatolia) is in dispute, most interpretations invoking climate changes. I propose that tectonic factors are a plausible alternative to explain repeated major lake level changes by up to 600 m (!). The tectonic Van Basin has been geodynamically active for a minimum of 600ky. For example, a major earthquake in 2011 resulted in 600 fatalities and significant fault-displacements in the lake basin. The hypothesis presented here will be tested by high-resolution dating and textural tephra analysis at four depth ranges of major lake level change intervals. Textures of reworked tephra sourced in active subalkaline Süphan and peralkaline Nemrut volcanoes, their active flanks extending into the deep lake basin, allow unambiguous source identification while harboring much information on reworking sites and mechanisms. The reworked tephras – particularly common in the intervals of seismically documented major lake level changes – will be sampled at high resolution and analyzed texturally and compositionally in detail. We will define diagnostic criteria that allow to distinguish in-situ reworking from far-field bottom-transport processes and to correlate diagnostic reworking textures to a range of water depths as well as to rates of fast vs. slow depth changes. Such process-oriented analysis of reworked intralake tephras is novel and will aid lake tephra specialists worldwide in exploring the interpretative potential of reworked tephras. Major lake level changes will be precisely dated by 40Ar/39Ar single crystal dating of anorthoclase. This detailed age structure of drastic lake level change intervals will be compared to dated and indirectly inferred tectonic processes (e.g. rise of Ahlat Ridge-Halepkalesi lineament). Our goal is to establish the Van system as a model for broad applications of highly variable depositional modes of reworked tephra in tectonically active lake basins that have experienced major lake level and climate changes.

在约600 ka（约220 m钻孔沉积物，包括约25%（至约500）原始和再加工的tephras）断裂的Van湖（安纳托利亚）演化过程中，主要湖泊水位变化的起源存在争议，大多数解释都涉及气候变化。我认为，构造因素是解释主要湖泊水位反复变化高达600米（!）的合理选择。构造范盆地的地球动力学活动至少有600天。例如，2011年的一次大地震导致600人死亡，湖盆发生了严重的断层位移。本文提出的假设将通过在主要湖泊水位变化区间的四个深度范围内进行高分辨率测年和纹理热像仪分析来验证。来自亚碱性sansphan火山和过碱性Nemrut火山的改造后的麻岩结构，其活动侧翼延伸到深湖盆地，可以明确地识别来源，同时还包含了许多改造地点和机制的信息。这些重新加工过的薄片——在地震记录的主要湖泊水位变化的间隔中尤其常见——将以高分辨率采样，并详细分析其结构和成分。我们将定义诊断标准，以区分原位再加工和远场底部输运过程，并将诊断再加工纹理与一系列水深以及快速与缓慢深度变化的速率相关联。这种以过程为导向的再造湖内tephras分析是新颖的，将有助于世界各地的湖泊tephras专家探索再造湖内tephras的解释潜力。主要的湖泊水位变化将通过斜长石的40Ar/39Ar单晶定年来精确定年。这种湖平面剧烈变化区间的详细年龄结构将与定年和间接推断的构造过程（如阿勒拉特岭-哈勒普卡莱西线的上升）进行比较。我们的目标是建立Van系统作为一个模型，在构造活跃的湖泊盆地中广泛应用高度可变的再加工层沉积模式，这些盆地经历了主要的湖泊水位和气候变化。