Luxembourg Sandstone Layer

Lux­em­bourg Sand­stone layer

The Grünewald with its approx­i­mate­ly 4500 ha, is sit­u­at­ed on the Lux­em­bourg Sand­stone lay­er, an impos­ing rock of about 42 m thick, that had been formed 190 to 170 mil­lions of years ago after the sed­i­men­ta­tion of the sea.

Geo­log­i­cal profile

The sand­stone is a porous and cracked rock, absorb­ing rain runoffs fil­ter­ing through the for­est soil to the low­er ground lay­ers. The Lux­em­bourg Sand­stone lay­er has become the most impor­tant nation­al reser­voir of drink­ing water, deliv­er­ing about 90% of the drink­ing water of the phreat­ic ground­wa­ter in Luxembourg.

The rain runoffs are fil­ter­ing through the per­me­able Sand­stone lay­er down to the imper­vi­ous Psilo­ceras lay­er, run­ning off side­ways at the inter­sec­tion point with the sur­face ground, called then Lay­er source.

The protection role Grünewald for the drinking water

The Grünewald as well as all oth­er forests, grow­ing on the Lux­em­bourg Sand­stone lay­er have a spe­cial impor­tance: they play a major pro­tec­tive role of the drink­ing water.

The rain runoffs are fil­tered through the dif­fer­ent lay­ers of the for­est soil and the ele­ments like dust or chem­i­cal pol­lu­tion, which have been fil­tered out by this process are in a long term stocked in the ground. By this way the for­est soil con­tributes large­ly to the clean­ing process of the dai­ly drink­ing water.

The springs of the Glaasburgronn

Nume­rous sour­ces emerge from the earth in the cut and very tight val­ley of the Glaasburgronn

At Glaas­bur­gronn, a v‑shaped val­ley sit­u­at­ed on the edge of the Grünewald, many lit­tle springs have its source in the Lux­em­bourg Sand­stone lay­er. Flow­ing togeth­er they form a brook, flow­ing off west­wards in the Alzette riv­er in Dommeldange.

The water of the Glaas­bur­gronn is of an excel­lent qual­i­ty, proofed by the pres­ence of all those ani­mal species that are only able to live in clean waters (for exam­ple Stone flies lar­vae and planarians).

Stone fly larva

Ema­na­tion of a source out of the Lux­em­bourg Sand­stone lay­er at the Glaasburgronn

Pla­nari­an