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

在约600 ka的古老(约220米钻探沉积物，包括约25%(高达约500)的原生和改造的冰盖岩层)向断层延伸的凡湖(安纳托利亚)演化过程中，主要湖面变化的起源存在争议，大多数解释是引用气候变化。我认为，构造因素是一种合理的替代方案，可以解释高达600米(！)的反复重大湖平面变化。构造范盆地的地球动力学活动至少持续了600ky。例如，2011年的一次大地震导致600人死亡，湖盆发生重大断层位移。本文提出的假设将通过高分辨率测年和主要湖泊水位变化区间的四个深度范围的结构tephra分析来验证。来自活动的亚碱性Süphan火山和过碱性Nemrut火山的重新加工的Tephra结构，其活动侧翼延伸到深湖盆地，允许明确的来源识别，同时包含大量关于重新加工地点和机制的信息。重新制作的冰盖--在地震记录的主要湖泊水位变化期间特别常见--将以高分辨率采样，并从质地和成分上进行详细分析。我们将定义诊断标准，以区分现场返工和远场海底输送过程，并将诊断返工结构与一系列水深以及快慢深度变化率相关联。这种以过程为导向的对修改后的湖内冰盖进行的分析是新颖的，将有助于世界各地的Tephra湖专家探索修改后的冰盖的解释潜力。主要的湖平面变化将通过斜长石的40Ar/39Ar单晶测年得到精确的定年。这种湖平面剧烈变化区间的详细年龄结构将与过时的和间接推断的构造过程(例如，Ahlat Ridge-Halepkalesi线的上升)进行比较。我们的目标是将VAN系统建立为在经历了重大湖平面和气候变化的构造活跃的湖盆中广泛应用高度可变的重新改造的火山灰沉积模式的模式。

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.