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The Rhenish lignite basin and the structure of plaques in the alluvial plain of the Lower Rhine

The origin of lignite

During the Tertiary period began in the basin of the Lower Rhine 30 million years of subsidence. This was the origin of a shallow sedimentation basin for the Rhine, Rur, Erft, Sieg and Meuse. This basin descended gradually and formed under the influence of tectonics, a rupture zone, while the massive schistose Rhine neighbor was uplifted. In several phases the North Sea original advance in that region. On top of the clay deposited in the basins were formed bogs, where the vegetation could not be broken down at the rate of poverty in oxygen in the water covering. The resulting peat was covered by continuous exchange of marine transgressions and regressions with gravel, sand and clay..

20-23 million years ago, in the early Miocene, the climatic conditions were favorable for marsh vegetation and peat formation. Gravel layers were deposited on the peat, they have a seal to air and their pressure has intensified the carbonization process. The peat was gradually transformed into lignite. Lignite is a fairly young fuel, which is early in the progression of the carbonization. Compared to coal, its heat capacity is low. The lignite water content is about 55%.

The open cast mines of Garzweiler, Hambach and Inden

Today, in “Ville”, the main group of layers, lignite can be found up to 70 meters thick. In the final phase of the Miocene were formed in the western area of ​​the basin, on the plate of the Rur, veins layers of Inden. During the Pliocene no veins were formed, instead, the region saw the enhanced tectonic agitation. The basin was broken along two main fault lines (Rurrand and Erft lines) into three plates, which have in turn trained smaller shifts of terrain and geological fracture fields (plates Rursee, the Erft and Venlo).

These plates sloping towards the north are inclined to different degrees and tilted at the same time to the east. A collapse because of different individual plates, lignite seams are now at different depths. While in the basement of City, they are near the surface – that’s why lignite mining has been started – they reach the plate to Erft (Hambach mine), a depth of more than 450 meters.

The lignite deposits in Rhineland contained on an area of ​​about 2,500 square kilometers originally about 55 billion tons. This makes it the largest homogeneous lignite deposits in Europe. Large parts of it are considered technically and economically exploitable. Lignite stock in approved surface mines amounted to 3.3 billion tonnes. The annual operating three open-pit mines Garzweiler, Hambach and Inden is 100 million tonnes.

Source : BUND-NRW-Braunkohle lignite Group of the BUND (Friends of the Earth) in NRW