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1 Markets I: The Ecosystem and Exchange-Traded Markets市场在线 2 Markets II: Rates, FX and Credit市场在线 3 Markets III: Commodities, Energy and Crypto市场在线 4 Quantitative Methods方法在线 5 Derivatives and Volatility衍生品在线 6 Rates, Credit, XVA and Risk利率、信用与风险在线 7 Research Craft: Predictors, Backtests, Measurement, Portfolios研究在线 8 Strategies I: Equities and Futures策略在线 9 Strategies II: Volatility, Relative Value, Macro and the Bank Desks策略在线 10 Microstructure and Execution交易执行在线 11 Market Making and High-Frequency Trading做市在线 12 Machine Learning for Markets机器学习在线 13 Low-Latency Software技术在线 14 Networks, Hardware and Trading Infrastructure技术在线 15 Research, Data and Risk Platforms技术在线 16 The Desk and the Firm公司运营在线 17 The Industry: Firms, Roles and Careers职业发展在线 18 Interviews I: Maths, Probability and Speed职业发展在线 19 Interviews II: Markets, Trading Games and the Final Round职业发展在线 20 Interviews III: Code职业发展在线

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Earth and Space Sciences · 术语表

什么是 Diachronous boundary？

Definition 24.6 University Earth and Space Sciences — Year 1 · 第 24 章 — The Stratigraphic Scale

A boundary is diachronous when its age changes from place to place along it. The boundaries of formations and of facies are commonly diachronous; the boundaries of chronostratigraphic units are, by definition, not.

A sandstone sheet laid down during a transgression (schematic, vertical scale exaggerated). The dashed lines t_1 to t_6 join points of equal age, t_1 the oldest. Where one meets the basement, it starts at the shoreline of its time; seaward it passes from sand to mud and, in the younger ones, to lime. The top of the sandstone lies between t_1 and t_2 in section 2 but between t_3 and t_4 in section 1: the formation boundary is diachronous, younger towards the land. — A sandstone sheet laid down during a transgression (schematic, vertical scale exaggerated). The dashed lines $t_1$ to $t_6$ join points of equal age, $t_1$ the oldest. Where one meets the basement, it starts at the shoreline of its time; seaward it passes from sand to mud and, in the younger ones, to lime. The top of the sandstone lies between $t_1$ and $t_2$ in section 2 but between $t_3$ and $t_4$ in section 1: the formation boundary is diachronous, younger towards the land.

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