Dating banded iron formation

How old is banded iron formation?

2.1 billion year old rock showing banded iron formation. Banded iron formations (also known as banded ironstone formations or BIFs) are distinctive units of sedimentary rock that are almost always of Precambrian age.

What is bedded iron formation?

Banded iron formations (BIFs) are iron ores defined as layered, bedded, or laminated stratigraphic units composed of ≥15% weight iron that often contain quartz, chert, or carbonate interlayers (James, 1954; Gross, 1980). Kent C. Condie, in Earth as an Evolving Planetary System (Third Edition), 2016

Why did the banded iron deposits end?

The requirement of an anoxic, but not euxinic, deep ocean for deposition of banded iron formation suggests two models to explain the end of BIF deposition 1.8 billion years ago. The Holland ocean model proposes that the deep ocean became sufficiently oxygenated at that time to end transport of reduced iron.

Why are there banded iron formations in the ocean?

Almost all of these formations are of Precambrian age and are thought to record the oxygenation of the Earths oceans . Banded iron formations are thought to have formed in sea water as the result of oxygen production by photosynthetic cyanobacteria.

What is the oldest type of banded iron formation?

Banded iron formations are found worldwide, in every continental shield of every continent. The oldest BIFs are associated with greenstone belts and include the BIFs of the Isua Greenstone Belt, the oldest known, which have an estimated age of 3700 to 3800 Ma.

What is the origin of banded rock formations?

Each band is similar to a varve, resulting from cyclic variations in oxygen production. Some of the Earths oldest rock formations, which formed about 3,700 million years ago ( Ma ), are associated with banded iron formations. They were first discovered in northern Michigan in 1844.

Why are there banded iron formations in the ocean?

Almost all of these formations are of Precambrian age and are thought to record the oxygenation of the Earths oceans . Banded iron formations are thought to have formed in sea water as the result of oxygen production by photosynthetic cyanobacteria.

Why did the banded iron deposits end?

The requirement of an anoxic, but not euxinic, deep ocean for deposition of banded iron formation suggests two models to explain the end of BIF deposition 1.8 billion years ago. The Holland ocean model proposes that the deep ocean became sufficiently oxygenated at that time to end transport of reduced iron.

How are banded iron formations formed on the ocean floor?

Photosynthetic organisms were making oxygen, but it reacted with the iron dissolved in seawater to form iron oxide minerals on the ocean floor, creating banded iron formations.

What caused the banding of iron in the Earths crust?

Because there was no more iron to rust in the oceans, oxygen entered the atmosphere. This event is the Great Oxygenation Event when the atmosphere first became oxygenated. And this event is what precipitated the banded iron formations. Other mechanisms have been proposed from GOE such as hydrothermal venting and bacterial oxidation.

Why are banded iron formations important?

Banded iron formations are major sources of iron ore for modern industry, but the last of these chemical sedimentary rocks formed over 800 million years ago. The history of banded iron formations is also the history of our planet’s journey from anaerobic to aerobic ecosystems.

Why did the banded iron deposits end?

The requirement of an anoxic, but not euxinic, deep ocean for deposition of banded iron formation suggests two models to explain the end of BIF deposition 1.8 billion years ago. The Holland ocean model proposes that the deep ocean became sufficiently oxygenated at that time to end transport of reduced iron.