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1 Primary & Middle School Mathematics1–9 年级在线 2 High School Mathematics10–12 年级在线 3 University Mathematics — Year 1本科一年级在线 4 University Mathematics — Year 2本科二年级在线 5 University Mathematics — Year 3本科三年级在线

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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 Ichnofacies？

Definition 20.9 University Earth and Space Sciences — Year 2 · 第 20 章 — Fossils and Palaeoenvironments

An ichnofacies is a recurrent association of trace fossils that reflects a set of environmental conditions; it is named after a characteristic trace.

The four marine ichnofacies of Seilacher’s model along a profile from the shore to the deep basin, with a sketch of a characteristic trace of each; depths are not to scale. The traces respond to energy, food and oxygen more than to depth as such.

示例

Example 20.10 (The base of the Varden cover)

The sandstone holds channel fills on scoured bases, roots and plant fragments, and no marine fossil: it was laid down by rivers on land. The oolitic limestone above has cross-bedded ooids, which grow as they roll in agitated water, vertical tubes and U-shaped burrows of the Skolithos ichnofacies, and worn shell fragments, all allochthonous: a shoal of the shoreface, swept by waves. Between the two the sea arrived: the contact records a marine transgression. In the order of Walther’s law, the river plain was followed by the shore, then the shoal.

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