The genesis of the Late Triassic landscape

The Ober­an­ven path is cross­ing a land­scape, formed by the Late Tri­as­sic lay­er dur­ing the Meso­zoic 200 mil­lions of years ago. In fact this lay­er is made by lime and clay sed­i­ments of an old pre­his­toric sea.
The gen­e­sis of the actu­al land­scape is result­ing from waters meet­ing the rocks.

In the past, the Late Tri­as­sic lay­ers did not yet appear on the sur­face, as they were cov­ered by thick Lux­em­bourg Sand­stone lay­ers. But lat­er on as these lay­ers fin­ished to be erod­ed, the Late Tri­as­sic lay­ers could be found on the surface.

The sed­i­ments of these Late Tri­as­sic lay­ers are com­posed by lime, clay and sand, form­ing an imper­vi­ous rocky ground, eas­i­ly deformable and ready to be erod­ed by waters. In con­se­quence rivers and brooks were able to “mod­el” those Late Tri­as­sic lay­ers with­out efforts. Dur­ing a long time the waters of the riv­er Syre and its afflux­es carved the Late Tri­as­sic lay­ers and con­tributed active­ly to the actu­al face of the land­scape. Slight­ly undu­lat­ed for­ma­tions were engen­dered and the land­scape with its smooth val­leys and undu­lat­ed hills was born.

Farming

An orchid on the “Aar­nescht”

The Late Tri­as­sic lay­ers, char­ac­ter­is­tic for their pas­tures and mead­ows had ever since been used for farm­ing by the inhabitants.

As these lay­ers can only store a lim­it­ed quan­ti­ty of water and nutri­ents for the veg­e­ta­tion, the Late Tri­as­sic soil is not very favourable for crop plants use. After a rain show­er the soil is very wet because of its high clay lev­el, the clay min­er­als swell and the ground becomes imper­vi­ous. There­fore the water, nec­es­sary to cul­ti­vate eco­nom­ic plants can­not enter the ground and flows out the surface.

Impor­tant rock steeps (cues­ta) are draw­ing the land­scape at the meet­ing point of the Late Tri­as­sic and the Lux­em­bourg Sand­stone layers.

At the north-east side of Ober­an­ven, in the very mid­dle of the Late Tri­as­sic land­scape, there lays one of the first nation­al nat­ur­al reserves in Lux­em­bourg: the “Aar­nescht”.

A very inter­est­ing didac­tic path is cross­ing this reserve, exhibit­ing one of the most impor­tant assort­ments of orchids in Luxembourg.