Banded Iron Formation: Distribution in Time and Paleoenvironmental Significance

Iron rich sediments are intermittently deposited throughout the earth's history, but almost all the important sediments of layered rocks, called iron formation, were in the Precambrian era. The current evidence is by no means decisive and shows the peak period of three deposition rates. The early Proterozoic sediments were far more than sediments of all other ages, in total they accounted for over 90% of the estimated total of 1,015 tons of initial sedimentary iron ore.

A large amount of iron deposits were seen in the iron layer of the strip. These strata are a type of rock in which alternating thin layers of iron oxide and less iron shale and meteorite belt alternate. These iron bands were built 3.7 billion years ago and 1.8 billion years ago. Starting from the historical time, the iron compounds mentioned are used as pigments (compared with meteorites) and also to the color of the various strata, eg Buntsandstein (Bunter, UK). In Germany's Eisensandstein (such as the Jurassic "iron sandstone" in Donzdorf and the UK bass stone) iron pigments contribute to the pale yellow color of many historic buildings and sculptures. The well-known red color of the surface of Mars comes from a weathered layer rich in iron oxide.

The structure of the striped iron is important as an indicator of the source of iron and the evolution of the atmosphere. The striped iron ore structure is a special sedimentary rock where alternating layers of iron-rich (red) and iron diffused (gray) layers overlap (Figure 7-4 on page 237). Most of this type of rock is over 2 billion years ago. They account for the majority of iron ore mined in the world today. Weak oxidation of iron formed by striped iron strongly indicates that oxygen has begun to accumulate in the environment at that time.

Striped iron structure is marine sedimentary rock consisting of alternating layers of red iron oxide and gray vermiculite. The Proterozoic Striped Iron Layer (BIF) is usually several hundred meters thick and can be spread over a wide area. In fact, they are the world's most important source of iron ore. Between 2.5 and 2 billion years ago, about 92% of the BIF was deposited early in Proterozoic. Oxygen in the atmosphere and oxygen in the sea were not enough, so they did not appear in large quantities before. Since early Proterozoic BIF formation events removed free iron from the oceans, later they did not occur in large quantities. They represent a unique interval for co-evolution of the Earth's atmosphere, hydrosphere and rock zone chemistry