Tuffite

A Tuffit is a rock that consists of 25 to 75% of pyroclastic (volcanic ejecta ); the remaining portion take Epiklasten ( clastic foreign material of volcanic and non- volcanic origin ) and non- pyroclastic a ( sediments ).

Definition

In common parlance, is commonly, but erroneously associated with the term Tuffit a mixed sediment of fine-grained sediment and volcanic ash. According to another view is outdated under a Tuffit principle any in the water ( subaquatisch ) remote volcanic ash understood, as opposed to on the ground ( subaerisch ) deposited volcanic ash.

In the recent literature a Tuffit is however only defined by the ratio of pyroclastics and non - pyroclastics, regardless of the grain size. A Tuffit must contain between 25 and 75 percent pyroclastics, the remainder may consist of Epiklasten or other nichtpyroklastischen components. To further division by the average grain size, the prefix can be used tuffitisch that is put in front of the corresponding rock ( according to grain size):

• Tuffitisches conglomerate (round components, diameter > 2 mm)
• Tuffitische breccia ( angular components, diameter > 2 mm)
• Tuffitischer sandstone (diameter 2 mm to 0.063 mm)
• Tuffitischer siltstone (or siltstone ) (diameter 0.063 mm to 0.002 mm)
• Tuffitischer mudstone (or mudstone ) (diameter < 0.002 mm)

Tuffites are a result of sedimentary transport usually well stratified and well sorted, and they may also contain fossils.

Formation

In tuffites two modes of formation can be distinguished. The primary Tuffit formed during a volcanic eruption, and is especially common in Plinian eruptions in appearance. The from the volcano ejected pyroclasts ( tephra ) are deposited in the surrounding areas and overburden while the water systems. Here there is a mixture of volcanic and fluvial sediment unconsolidated material. The secondary Tuffit formed after a volcanic eruption, when the still unconsolidated pyroclastic deposits are removed and put into a water system, where they mix with the sediment.