Diamictite

Diamictite (Greek δια (dia - ): by and μεικτός ( meiktós ): mixed) is a conglomerate or breccia a little or unsorted rock that can contain in a clayey or silty matrix very different clasts. At least 25 % of these rock fragments of a Diamiktits larger than 2 mm. The clasts are angular to rounded and can come from a different rocks consist, for example, from different sedimentary rocks, metamorphic or igneous rocks. The mixing of the components is done by sedimentary processes. Raw Firms such sediment is called Diamikt.

The term was introduced in 1960 from Flint, Sanders and Rodgers as a purely descriptive name for almost sorted and poorly stratified rocks, which allows in contrast to Tillit no conclusion on a particular formation.

Creation processes

Despite the purely descriptive definition diamictite is often mistakenly equated with the term tillite and so exclusively associated with a glacial formation about by glaciers in conjunction, although diamictites can be brought about by a number of geological processes.,

Formation by glacial processes

Diamictites arise as a direct result of ice movement of glaciers or ice streams by the deposition as glacial tills (Till ) in end, side or ground moraines. Proportion of these deposits have both rock fragments each grain size, which were transported as debris on and in the glacier and deposited on the sides or front of the end of the ice, as abraded by the ice, especially at its sole and mixed during transport rocks from the subsurface. Rare direct from rendering contained in the ice rubble is responsible for the formation of Diamiktiten, as well as the deposition of rock debris by mass movements such as avalanches, the slip off the edge of the ice and come on land or under water to rest.

With glacial processes is also associated with the melting out of rock from verdrifteten icebergs or defrosting ice sheets, in which fine particles - as they also occur in the runoff water - and drop the rock pieces after melting out on the sea or seabed and there normally deposited with there mixed sediments to the deposit. In so incurred, predominantly fine -grained sediment are found frequently significantly coarser rock fragments that have deformed the still soft soil layer on impact from above. Such drop Stones can also form by other processes, however.

Diamictites may eventually result from the combination thrust of soil material at ground contact and the stranding of icebergs. Such operations are not limited to extensive glaciations, they can also be seasonal growing ice occur.

Formation by volcanic processes

As part of the activity of volcanoes can volcanic mudflows ( lahars ) arise in which carried away large masses of water volcanic material and other rocks of the ground with great force and mix thoroughly. These mudflows can ashore to travel long distances and may be found as a submarine mudflow a continuation in lakes or in the ocean. Can according to the transporting force of the mud flow, so the frozen -mixed sediment without the different components of different origins segregate by their buoyancy in layers of different density.

Formation by rearrangement processes

Diamictites in the marine environment caused by mass movements such as debris flows (English: debris flows), suspension flows and Olisthostrome. In these processes, material is of different origin and grain size mixed and deposited unsorted. The mixing of already deposited sediment by submarine landslides leads to a thorough mixing of miscellaneous material. The emergence of Diamiktiten by submarine mass flows as suspension flows and Olisthostrome in tectonically active areas is the most common mode of origin of these rocks. When the tectonic activity in connection with the Überschiebungstektonik a nascent emergence of wrinkles in the mountains is that sequences that contain diamictites of such resulting, called flysch are.

Furthermore Diamikte can also occur on the mainland by material surroundings. Especially in the polar regions affects the solifluction, which produces intense displacement and mixing processes, thus leading to the emergence of a well-mixed deposits.

In arid climate cause sporadic but for torrential rains to flush occurring large masses of weathering debris from the mountains and the deposition of these masses on the edge of the mountains in the form of alluvial fans ( Alluvialfächer ). Also in this case arise typical, usually conglomeratic Diamictites, also referred to as fanglomerates. If it is in these Fanglomeraten to the erosion debris of a young, located in raising wrinkles Mountains, they fall under the heading of molasses.

Other geological processes

Diamictites can be generated by tectonic processes by rock breakage, transport and mixing in fault zones in some cases to form a Störungsbrekzie lead, occur in the next larger finely grated rock fragments. Depending on the transport distance of the disturbance and the composition of the affected rock layers may be involved very different rocks in the construction of Diamiktits.

The situation created by erosive processes weathering cover ( regolith ) can result in some embodiments to form a rock, found in the rubble of rearrangement processes and remnants of the original rocks of various sizes along with fine weathered material.

Rarely occur Diamictites by extraterrestrial caused processes. When a meteorite impact the upcoming spot rocks are shattered into fragments of various sizes, ejected and deposited unsorted again. An example of such masses of rubble is the Bunte Breccia, which was created when a meteorite about 15 million years ago in the Ries ( Ries event). If the rocks involved converted by heat and pressure, then a Impaktit, which is, however, no longer be regarded as metamorphic rock as diamictite.

Occurrence

Diamictites occur in all parts of the world, such as in the following geological units:

• Till than or Tillit in all glaciated regions of the world
• Leather shale in the Thuringian Slate Mountains
• Geschwend - Sengalenkopf unit in the Black Forest
• Bunte Breccia in the Ries
• Granville lineup, Brittany
• Fiq Formation in Oman
• Chuos and Ghaub Formation in Namibia
• Witwatersrand and Dwyka diamictites -, South Africa
• Rio Ivaí lineup and Itararé Group in the Paraná Basin, Brazil
• Windermere Supergroup in North America
• Elatina Formation in Australia