Jotnian

In north European geology, Jotniansediments are a group of Precambrian rocks more specifically assigned to the Mesoproterozoic Era (Riphean), albeit some might be younger. Jotnian sediments include the oldest known sediments in the Baltic area that have not been subject to metamorphism. Stratigraphically, Jotnian sediments overlie the rapakivi granites and other igneous and metamorphic rocks and are often intruded by younger diabases.

Jotnian sediments include quartz-rich sandstones, siltstones, arkose, shale and conglomerates. The characteristic red colour of Jotnian sediments is due to their deposition in subaerial (e.g. non-marine) conditions. Jotnian sediments are the oldest known sediments in the Baltic area that have not been subject to metamorphism.

Their age is poorly constrained, but generally they are younger than the rapakivi granites and older than Postjotniandiabases that intrude the sediments. This means that Jotnian sediments were deposited approximately 1600–1260 millions years ago. Some Jotnian sediments are, however, younger than the diabases, meaning they can be younger than 1260 million years. Jotnian sediments are usually assigned to the Riphean Stage of the Mesoproterozoic Era. Jotnian sediments rests on what is known as Subjotnian rocks which include weathered rapakivi granites and the Hogland Series. Amantov and co-workers comments about the terms Jotnian and Postjotnian that:

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