Paleomagnetic constraint on the Age of the Shyok Suture Zone

The India-Eurasia collision is a key case study for understanding the influence of plate tectonic processes on Earth’s crust, atmosphere, hydrosphere and biosphere. However, the timing of the final India-Eurasia continental collision is debated due to significant uncertainty in the age of the collision between the Kohistan-Ladakh arc and Eurasia along the Shyok suture zone. Here we present paleomagnetic results that constrain the Karakoram terrane in northwest India to a paleolatitude of 19.9 ± 8.9 °N between 93 – 75 million years ago (Ma). Our results show that the Karakoram terrane was situated on the southern margin of Eurasia in the Late Cretaceous. Our results indicate that the Kohistan-Ladakh arc and Eurasian continent had not converged until < 61.6 Ma, placing a Paleocene older limit on the age of final closure of the Shyok suture zone. This suggests that the India-Eurasia collision in northwestern India likely occurred after the closure of the oceanic basin between the Kohist..., We collected 7–10 oriented core samples from 34 horizons distributed throughout the Saltoro Formation stratigraphy near Charasa for paleomagnetic analysis. Bedding orientations at each site were measured repeatedly over a 20–40 m along-strike, and the bedding orientation used for structural corrections is the mean of 5–15 individual measurements. Andesite bedding horizons were identified using chilled upper surfaces of beds. Core samples were collected in the field using a water-cooled electric hand drill and oriented using an ASC Industries Pomeroy orienting fixture. Nonmagnetic brass tools were used to extract cores from the outcrop to prevent damaging the remanent magnetization of samples during sample collection. Optical microscopy was used to identify magnetic carriers and textural relationships within the samples. One specimen was cut from each core sample using an ASC Scientific dual-blade rock saw. The natural remanent magnetization was measured on a 2G Enterprises Superconducti..., Software package used: PmagPy
Tauxe, L., R. Shaar, L. Jonestrask, N. L. Swanson-Hysell, R. Minnett, A. A. P. Koppers, C. G. Constable, N. Jarboe, K. Gaastra, and L. Fairchild (2016), PmagPy: Software package for paleomagnetic data analysis and a bridge to the Magnetics Information Consortium (MagIC) Database, Geochem. Geophys. Geosyst., 17, doi:10.1002/2016GC006307., # Paleomagnetic constraint on the Age of the Shyok Suture Zone

The dataset contains the results of thermal demagnetization experiments.

## Description of the data and file structure

Thermal demagnetization data is stored in separate files for different levels of analysis. Raw superconducting rock magnetometer data is saved in .UP and .stat files for each run at a given temperature step. Thermal demagnetization magnetic moment and directional data for each is sample is stored in .rmg files labelled by sample number. Data from each site can be imported into PmagPy using the .sam files.

印度-欧亚碰撞是理解板块构造过程对地球地壳、大气圈、水圈和生物圈影响的关键研究案例。然而，由于沿绍约克缝合带（Shyok suture zone）的科希斯坦-拉达克弧（Kohistan-Ladakh arc）与欧亚大陆的碰撞时代存在显著不确定性，印度-欧亚大陆最终碰撞的时间仍存在争议。本文报道了古地磁（paleomagnetic）研究结果，限定了印度西北部喀喇昆仑地体（Karakoram terrane）在93至75百万年（Ma）期间的古纬度为19.9 ± 8.9°N。研究结果表明，喀喇昆仑地体在晚白垩世（Late Cretaceous）位于欧亚大陆南部边缘。本研究显示，科希斯坦-拉达克弧与欧亚大陆直至61.6 Ma前才发生汇聚，为绍约克缝合带最终闭合的时代设定了古新世（Paleocene）的更早上限。这表明印度西北部的印度-欧亚碰撞很可能发生在科希斯坦……之间的洋盆闭合之后。

我们在查拉萨附近的萨尔托罗组（Saltoro Formation）地层分布的34个层位采集了7~10块定向岩心样品用于古地磁分析。每个采样点的层理产状沿走向20~40 m范围内重复测量，用于构造校正的层理产状为5~15次单独测量的平均值。利用岩层淬火顶面识别安山岩（andesite）层理层位。野外采样使用水冷电动手持钻机完成，采用ASC工业公司Pomeroy定向夹具进行定向。采集岩心时使用非磁性黄铜工具从露头取出样品，以避免采样过程中破坏样品的剩余磁化强度（remanent magnetization）。利用光学显微镜识别样品中的磁性载体和结构关系。从每块岩心样品中使用ASC科学公司双刀片岩石锯切割出1个试样。在2G企业公司超导……磁力仪上测量天然剩余磁化强度（natural remanent magnetization）……

所用软件包：PmagPy
Tauxe, L.、R. Shaar、L. Jonestrask、N. L. Swanson-Hysell、R. Minnett、A. A. P. Koppers、C. G. Constable、N. Jarboe、K. Gaastra及L. Fairchild（2016），《PmagPy：古地磁数据分析软件包及通往磁学信息联盟（MagIC）数据库的桥梁》，《地球化学、地球物理学、地球系统》，17卷，doi:10.1002/2016GC006307.
# 绍约克缝合带时代的古地磁约束
本数据集包含热退磁（thermal demagnetization）实验结果。

## 数据与文件结构说明
热退磁数据按不同分析层级分别存储于不同文件。每个温度步骤的原始超导岩石磁力仪数据保存为.UP和.stat文件。每个样品的热退磁磁矩与方向数据存储在以样品编号命名的.rmg文件中。各采样点的数据可通过.sam文件导入PmagPy软件包。