The Flammenmergel is a lithological

Lithology

The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples or with low magnification microscopy, such as colour, texture, grain size, or composition. It may be either a detailed description of these characteristics or be a summary of...

 unit of the Lower Chalk in Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

.

In Niedersachsen (Lower Saxony

Saxony

The Free State of Saxony is a landlocked state of Germany, contingent with Brandenburg, Saxony Anhalt, Thuringia, Bavaria, the Czech Republic and Poland. It is the tenth-largest German state in area, with of Germany's sixteen states....

) it reaches a depth of 110 to 150 m in the area of the Sackmulde (a fold in the Germanic Basin). The Flammenmergel gets its name from its "flamed" or "burnt" appearance.

According to JORDAN(1968), this appearance is caused by the tracks of burrowing organisms, which consist primarily of siliceous sponge spicules which have been washed into the burrows. The silicic acid, when weathered, forms black streaks, which give the rock its characteristic appearance. Jordan divides the Flammenmergel into five units. The Flammenmergel is a slightly clayey to slightly sandy marl

Marl

Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...

. It is yellow to ochre in colour, whereas the streaky "flames" are dark grey to black. The rock is siliceous and hard.