A core drilled near Wolhaarkop in Griqualand West, South Africa, intersected highly oxidized Kuruman Iron Formation below red beds of the Gamagara Formation. The lateral equivalents of the Kuruman Iron Formation in this drill hole consist largely of siderite, ankerite, magnetite, greenalite, and quartz. The oxidation of the Kuruman Iron Formation in WOL 2 occurred almost certainly during weathering prior to the deposition of the Gamagara Formation. The date of this weathering episode is bracketed between about 2.2 and 1.9 bybp by the age of the Ongeluk lavas in the Transvaal sequence below the unconformity and by the age of the Hartley lavas in the Olifantshoek Group above the unconformity. The ratio of iron to SiO2 in the several facies of the weathered Kuruman Iron Formation in WOL 2 is nearly the same as that in their unweathered equivalents. Since SiO2 loss during weathering was almost certainly minor, the similarity of the Fe/SiO2 ratio in the weathered and unweathered BIF indicates that nearly all the "FeO" in the Kuruman Iron Formation was oxidized and retained as FeO3 during weathering. Such a high degree of iron retention is best explained by an O2 content of the atmosphere > or = 0.03 atm at the time of weathering. Such an O2 pressure is very much greater than that suggested by the composition of paleosols developed on basalt > or = 2.2 bybp but is consistent with the highly oxidized nature of the 1.85 by Flin Flon paleosol. The new data suggest that PO2 rose dramatically from about 1 percent PAL (present atmospheric level) to > or = 15 percent PAL between 2.2 and 1.9 bybp.

中文翻译：

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南非西格里夸兰德州的一次古风化剖面：证据表明大气氧在2.2和1.9 bp之间急剧上升。

南非Griqualand West的Wolhaarkop附近钻出的岩心在Gamagara组红色层下方相交了高度氧化的Kuruman铁组。该钻孔中库鲁曼铁层的侧向等效物主要由菱铁矿，铁矿石，磁铁矿，绿辉石和石英组成。几乎可以肯定，在WOL 2中库鲁曼铁层的氧化发生在风化之前，其沉积在Gamagara层之前。该风化事件的发生日期由不合格以下的德兰士瓦火山序列中昂格鲁克熔岩的年龄和不合格以下的奥利芬舒克群中哈特利熔岩的年龄括在大约2.2和1.9个bp之间。WOL 2中风化的库鲁曼铁层的几个相中铁与SiO2的比例与未风化的当量中的比例几乎相同。由于风化过程中SiO2的损失几乎可以确定，因此风化和未风化BIF中Fe / SiO2比的相似性表明，在风化过程中，库鲁曼铁层中几乎所有的“ FeO”都被氧化并保留为FeO3。如此高的铁保持力最好用风化时大气中O2含量≥0.03 atm来解释。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2从2.2％到1.9 bp的PAL急剧上升（从目前的大气水平）上升到≥15％的PAL。Fe / SiO2比在风化和未风化的BIF中的相似性表明，在风化过程中，库鲁曼铁层中几乎所有的“ FeO”都被氧化并保留为FeO3。如此高的铁保持力最好用风化时大气中O2含量≥0.03 atm来解释。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2从2.2％到1.9 bp的PAL急剧上升（从目前的大气水平）上升到≥15％的PAL。Fe / SiO2比在风化和未风化的BIF中的相似性表明，在风化过程中，库鲁曼铁层中几乎所有的“ FeO”都被氧化并保留为FeO3。如此高的铁保持力最好用风化时大气中O2含量≥0.03 atm来解释。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2从2.2％到1.9 bp的PAL急剧上升（从目前的大气水平）上升到≥15％的PAL。在风化过程中，库鲁曼铁层中的铁被氧化并保留为FeO3。如此高的铁保持力最好用风化时大气中O2含量≥0.03 atm来解释。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2从2.2％到1.9 bp的PAL急剧上升（从目前的大气水平）上升到≥15％的PAL。在风化过程中，库鲁曼铁层中的铁被氧化并保留为FeO3。如此高的铁保持力最好用风化时大气中O2含量≥0.03 atm来解释。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2从2.2％到1.9 bp的PAL急剧上升（从目前的大气水平）上升到≥15％的PAL。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2在2.2和1.9 bp范围内从大约1％的PAL（当前的大气水平）急剧上升到大于或等于15％的PAL。这样的O2压力远远大于玄武岩上大于等于2.2bp的古土壤组成所暗示的压力，但与Flin Flon古土壤的1.85高度氧化性质相符。新数据表明，PO2从2.2％到1.9 bp的PAL急剧上升（从目前的大气水平）上升到≥15％的PAL。