中文摘要：

铁在不同温度和湿度环境中形成不同铁的化合物，如铁的氧化物、氢氧化物、硫化物和碳酸盐等。这些不同种类含铁矿物可以通过磁学方法测量，根据它们含量与比例特征来分析过去地球环境变化。黄土是一种风积形成特殊成因的沉积岩，经过百余年不断争论，才有了“风成”的定论。本文总结概括世界各地的黄土古土壤形成环境与铁矿物特征，得到如下认识：红色古土壤只形成于干旱氧化环境中，但不是所有干旱条件都能够形成红色土；红色土壤中的磁赤铁矿和赤铁矿在湿润氧化和还原环境中不稳定，会渐渐转变成为氢氧化物（褐铁矿），甚至硫化物（黄铁矿/磁黄铁矿），导致红色褪去、黄色增加和磁化率降低。现代的河流、湖泊和海洋均为还原环境，沉积物也呈黄、灰、白、绿、黑等还原系列颜色与之对应。将今论古可以推理，过去红色地层极不可能形成于“水成”环境，只能形成于地表透水性良好的干燥氧化环境中。沉积岩除了“水成”和“风成”两个大类环境之外，至少还有一种过渡交互类型需要得到特别认识，如干旱区山间盆地洪积类型（戈壁滩洪积与河流河漫滩等环境）。这类沉积物毫无疑问是洪水搬运形成，因此留下层理等特征；但是洪水消失后，沉积物实际上长期处于地表干燥氧化成土环境，因此兼有水成和成土两种特征。丹霞红层具有水成层理，并同时具有原生红颜色的就是在这样环境中形成的。张掖彩色丘陵，并非湖相水成地层，而主要是风积古土壤地层序列，在长期持续炎热半干旱环境条件下甚至还发育了特殊的厚层石膏土。黄土与环境的深入研究必将对地质学和地理学产生深远的影响，比如黄土研究已经带来地学一些基本概念变化，如：古土壤层并不一定意味着沉积间断；层状沉积岩地层并不一?

英文摘要：

Iron is a common and abundant element in the Earth crust. It forms various iron compounds such as iron oxides, hydroxides, sulfides and carbonates at different temperatures and humidity. These various types of iron bearing minerals and their ratios can be approximated by magnetic measurements for analyzing environmental change of the Earth in past. Eolian loess is a sediment formed from silt deposited by wind This paper summarizes loess paleosol formation environment around the world and their iron mineral characteristics. The following conclusions are reached. Red paleosols form in oxidizing environments of well drained soils. Reddish maghemite and hematite in moist and chemically reducing environments are unstable and transformed into hydroxides （goethite） , carbonates （siderite） or sulfides （pyrite）. Modern rivers, lakes and oceans are reducing sedimentary environments, and their sediments are yellow, gray, white, black and other colors of chemical reduction. By this reasoning for the past, the formation of the red color is formed on the Earth surface in well drained oxidizing environments. In addition to ＂water lain＂ and ＂wind blown＂ sediments alluvial environments include waterlain flood deposite that are exposed to weathering and oxidation in paleosols. Such sediments is undoubtedly flood transported, thus leaving bedding and other water lain characteristics. But floodwaters waters dissipate soon, leaving the sediments for a long time oxidized pedogenic environments. Cretaceous China Danxia was formed in such alluvial environments. This process occurs in deserts, where soils gain gypsum, calcite and other salts in addition to oxidative weathering. Such paleosols are common in the Quaternary Loess Plateau of China and in Zhongguo Formation of Zhanye Danxia. The process also occurs in humid well drained floodplains where base poor clays develop with oxidative weathering, but salts are leached from the profile, as in the Xiagou Formation of Zhanye Danxia. These paleosols reflect conditions