Réserve naturelle nationale d'Hettange-Grande

The Réserve naturelle nationale d'Hettange-Grande is a small but scientifically significant geological nature reserve located in the commune of Hettange-Grande, north of Thionville, in the Moselle department of Grand Est, just a short distance from the border with Luxembourg. Covering roughly 6 hectares, the protected area encompasses the site of a former quarry known as Gries, today visited mainly by geologists, paleontologists and anyone curious about Earth history.

Why is this site so significant?

Established in 1985, the reserve exists primarily to protect an exceptional rock exposure recognized internationally as the stratotype of the Hettangian stage — the oldest stage of the Lower Jurassic, spanning roughly from 199.6 to 196.5 million years ago. It was here, in the old quarry, that Swiss geologist Eugène Renevier proposed in 1864 that this location serve as the international reference point for the newly defined geological stage. In practical terms, this means the rock layers exposed at Hettange-Grande are the benchmark against which comparable formations found anywhere in the world are measured.

What can visitors see at the reserve?

The centerpiece of the site is a wide, open rock amphitheater with a cliff face rising to around 18 meters. The exposed wall reveals successive layers of different rock types — sandstone, limestone and marl — stacked in a clearly legible stratigraphic sequence. This exposure also allows visitors to observe faults and distinctive bedding surfaces, offering a rare, tangible view into the geological history of the region from nearly 200 million years ago.

The reserve is equally notable for its fossil richness. The rock layers have yielded traces of ancient flora alongside a wide variety of marine organisms, including foraminifera, ostracods, bivalves, gastropods and cephalopods, as well as vertebrate remains. This diversity has led scientists to treat the site as something of an archive of early Jurassic life.

How can the reserve be visited?

The former quarry is open to visitors via a marked interpretive trail that winds past the main viewpoints and rock exposures. Information panels along the way explain the significance of the different rock layers and recount the history of geological discovery at the site. The walk requires no special physical preparation and is accessible to visitors of most ages, though care should be taken near the cliff edge.

The surrounding area, known as Soetrich, also offers opportunities for longer walks through the green spaces that surround the former quarry, making the location appealing both to those interested in geology and to visitors simply looking for a quiet nature outing.

Frequently asked questions

Where exactly is the reserve located? The reserve lies in the commune of Hettange-Grande in the Moselle department, in an area known as Soetrich, north of Thionville and close to the border with Luxembourg.

Why is this site important to geologists? Because it hosts the international stratotype of the Hettangian stage, the reference exposure defining the oldest stage of the Lower Jurassic, established in 1864.

Can fossils be found at the reserve? Yes, the site is rich in marine fossils (bivalves, gastropods, cephalopods, foraminifera, ostracods) as well as traces of ancient vegetation, though collecting fossils within the reserve itself is not permitted.

Is the reserve suitable for family visits? Yes, the marked trail and information panels make it accessible for both adults and children interested in nature and geology.