Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years

The lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by ⁴⁰Ar/³⁹Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic–anoxic boundary, for example, lake‐level highstands during interglacials/interstadials; (iii) CaCO₃‐rich banded sediments which are representative of a lowering of the oxic–anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO₃‐poor banded and mottled clayey silts reflecting an oxic–anoxic boundary close to the sediment–water interface, for example, lake‐level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp . Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years.     

地震数据存储的设备安全与应用安全

对于地震数据管理中心来说,地震数据的安全性和可用性极为重要,重要的数据(不管是在线的还是离线的)一旦被破坏或丢失,就会给我们的工作造成重大的影响,甚至是难以弥补的损失。将损失降至最小的最行之有效的办法莫过于地震数据的安全存储。地震数据的安全存储离不开数据的安全备份。数据的安全备份来自设备安全和应用安全两个方面。本文重点论述地震数据存储的设备安全与应用安全的要点和常见误区。     

基于DBnet和众筹策略的气象纸质表格快速数字化方法及系统

气象纸质表格历史资料有很高的科学研究价值和很重要的历史保留意义。数字档案通过数字化的方式将纸质原始资料进行收集、保存和提供各类数字信息资源。本文提出了一种“纸质表格扫描成像”+“图像碎片化处理”+“众筹识别”的快速数字化方法及系统，利用气象大数据资源，应用DBnet模型、DSCC算法等技术对纸质气象表格扫描图像进行图像碎片处理；通过用户的登录行为实现“众筹录入”，完成气象纸质表格资料的数字化档案工作。经验证，快速数字化系统的一录正确率约为99.7%，高于传统数字化人工键入的一录正确率（95.6%）；录入时效比传统数字化提高了22.2%。该系统保证了数据正确性、提高了工作效率，实现了气象纸质表格资料快速形成数字档案的目标，也为数字档案工作提供了新的思路；在新冠疫情导致传统数字化人工聚集工作模式面临较大风险的背景下，具有一定的现实意义。