The Bailadila Group of the Bastar Craton, India, is host to a 200-m-thick banded iron formation (BIF). We document the lithostratigraphic context for the BIF, informally referred to as the Bose iron formation, and provide radiometric constraints for its depositional age. Field evidence illustrates that the BIF was deposited on an inner-shelf succession with a quartz arenite that grades upward into the BIF through storm-dominated offshore shelf deposits. The quartz arenite to BIF transition records a relative sea level rise from transgressive to highstand systems tract when the BIFs were deposited in a starved outer continental shelf. U-Pb SHRIMP analyses of zircons from the basement of the Bailadila Group yielded mostly highly discordant U-Pb SHRIMP ages. However, the ages fall on well-defined discordia lines from which concordia intercept ages could be determined. These ages, in combination with the ages of a few zircons that are less than 6% discordant, indicate that the granitoid basement crystallized at 3500–3550 Ma. The maximum depositional age of the Bailadila Group is constrained from the weighted mean ²⁰⁷Pb/²⁰⁶Pb SHRIMP age of $2725\pm 57$ Ma from detrital zircons from the basal arenites. A well-constrained weighted mean ²⁰⁷Pb/²⁰⁶Pb SHRIMP age of $2733\pm 53$ Ma for zircons from a unit that unconformably overlies the Bailadila Group is within error of that age. Stratigraphic relationships suggest that the Bailadila succession is unconformably overlain by the ~2.5 Ga Kotri and Dongargarh Supergroups. The depositional age of the Bailadila Group is well constrained between ~2.7 and 2.5 Ga. In contrast to most other Archean Algoma-type iron formations of peninsular India, which are closely related to volcanic rocks in greenstone belts, the Bose iron formation is associated with siliciclastic shelf succession. It thus is considered a Superior-type iron formation that represents the oldest known one of its kind in India.

中文翻译：

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印度巴斯塔克顿的巴切里铁矿开采区带状铁层-轴承的拜拉迪拉群的地层学，沉积环境和SHRIMP U-Pb年代学

印度Bastar Craton的Bailadila集团拥有200米厚的带状铁矿（BIF）。我们记录了BIF的岩石地层学背景，非正式地称为Bose铁形成，并为其沉积年龄提供了辐射约束。现场证据表明，BIF沉积在一个内层架上，并带有一个石英砂岩，该石英砂岩通过风暴为主的近海陆架沉积物逐渐上升到BIF中。当BIF沉积在挨饿的外陆架中时，石英砂从BIF过渡到海平面从海侵系统上升到高位系统。对Bailadila集团地下室的锆石进行U-Pb SHRIMP分析后，得出了大多数不一致的U-Pb SHRIMP年龄。然而，年龄落在明确的迪斯科舞线上，从中可以确定一致的拦截年龄。这些年龄，加上一些锆石的年龄小于6％不一致，表明花岗岩基底在3500-3550 Ma处结晶。加权平均数限制了Bailadila组的最大沉积年龄²⁰⁷ Pb / ²⁰⁶ Pb SHRIMP的年龄$2725\pm 57$Ma来自基岩的碎屑锆石。严格限制的加权平均年龄²⁰⁷ Pb / ²⁰⁶ Pb SHRIMP的年龄$2733\pm 53$Ma代表来自Bailadila集团不合身的单位的锆石，在那个年龄的误差范围内。地层关系表明，〜2.5 Ga Kotri和Dongargarh Supergroups一致覆盖了Bailadila继承。拜拉迪拉群的沉积年龄被很好地限制在〜2.7和2.5 Ga之间。与印度半岛的其他大多数太古宙阿尔戈玛型铁地层（与绿岩带中的火山岩密切相关）相反，Bose铁地层与硅质碎屑层架演替。因此，它被认为是高级型铁层，代表了印度同类中最古老的铁层。