Slate / Blue Devonian Slate (Mosel: Heat Absorption; Petrol in Aged Riesling)

Moselwein e.V., the Mosel's regional wine body, traces the region's slate to the Devonian, about 400 million years ago, when a primeval ocean covered today's Mosel country and sediment layers several kilometres thick built up on its floor. When the ancient continents Gondwana and Laurussia collided, that ocean was pushed together between the plates and its floor compressed under enormous pressure and high temperatures; the sediments became slate, which folded up into a mountain range, the Rheinisches Schiefergebirge. About 15 million years ago the ancestral Mosel began to shape the landscape: as the slate uplands rose, its once broad, straight bed cut deeper and grew more winding. Moselwein e.V. says half of the region's vineyard area (no year given) lies on Devonian slate in blue, grey, brown and reddish shades, often so finely layered that it can be broken by hand, and that the rock weathers easily. The Lower Mosel, or Terrassenmosel, between Zell and Koblenz differs: there quartzitic sandstones with silt and clay slate make up most of the soils. DWI adds that the roots of the vines penetrate deep into the ground to seek water and minerals.

• Origin (Moselwein e.V.): Devonian ocean sediments, compressed under enormous pressure and high temperatures when Gondwana and Laurussia collided, became slate
• Colour and texture (Moselwein e.V.): blue, grey, brown and reddish; often so finely layered it breaks by hand; the 400-million-year-old rock weathers easily
• Soils by sub-region (DWI): clayish slate and greywacke in the lower Mosel, Devonian slate in the steep sites of the middle Mosel, primarily shell limestone in the upper Mosel; Moselwein e.V. describes the Saar's soil as predominantly dark Devonian slate, with diabase, a rock of volcanic origin, in some sites
• Ürzig exception: Moselwein e.V. says rhyolite, a volcanic rock of entirely different origin, occurs only within the boundaries of Ürzig on the great Mosel bend; the VDP describes the Würzgarten's soil as red weathered slate with a high rock content, its vivid colour from high iron concentrations

DWI says the protected valley location makes the Mosel one of the warmest climates in Germany, and that the steep slate slopes above the rivers store the sun's heat during the day and release it again at night. Jancis Robinson writes that local growers know Riesling can be ripened only on the sunniest south- and south-west-facing sites, steep enough and close enough to the river to benefit from its function as mirror, on porous slate soils that drain away the region's frequent surplus rainfall and "retain daytime heat to act as night storage heaters". Moselwein e.V. calls slate's heat storage a considerable advantage in cool autumn nights. At site level, the VDP says the dark soils of stony weathered Devonian slate in the Bernkasteler Doctor serve as an additional heat store while securing water supply through their water-holding capacity.

• Heat storage (DWI): steep slate slopes store the sun's heat by day and release it at night
• River as mirror (Jancis Robinson): the best sites face south or south-west and sit steep enough and close enough to the river to benefit from its function as mirror
• Slope (VDP): the Doctor faces the Mosel at up to 70 percent and the Würzgarten's Riesling grows on slopes up to 80 percent steep
• Drainage (Jancis Robinson): porous slate soils drain away the region's frequent surplus rainfall

The Australian Wine Research Institute (AWRI), in a 2012 report in the Wine & Viticulture Journal, describes TDN (1,1,6-trimethyl-1,2-dihydronaphthalene) as having been called 'delicious' but 'undesirable' in excess, because it can give a kerosene-like aroma in some wines, depending on the age of the wine and individual preference. The AWRI calls it an important part of the bottle-aged bouquet of Riesling, with levels up to six times higher than in other varieties. Free TDN is generally not present in significant quantities in grapes or juice. Its formation depends on carotenoids, which build up in the early stages of fruitset and break down from veraison onwards into C13-norisoprenoids; these, including compounds that give rise to TDN, may attach to sugar molecules, forming a slow-release flavour reservoir from which TDN can emerge during storage. The AWRI calls sun exposure by far the most studied and accepted contributor to TDN, and says concentrations increase with bottle age and that more acidic wines have been shown to develop TDN more quickly than others. The report addresses Riesling generally; it does not attribute TDN to slate.

• Formation (AWRI): grape carotenoids break down from veraison into C13-norisoprenoids, including the compounds that give rise to TDN, which can emerge during storage
• Detection (AWRI, citing Sacks et al. 2012): the sensory detection threshold, once believed to be 20µg/L, was revised to 2µg/L, and 50% of the population should be able to perceive (but not necessarily recognise) TDN in most Riesling wines
• Vineyard factors (AWRI): TDN and its precursors increase when grapes are exposed to sunlight and warm temperatures; early harvesting and shading berries are two management strategies
• Bottle factors (AWRI): concentrations increase with bottle age; in one study, samples stored at 30°C showed considerably higher increases than those stored at 15°C; cork and synthetic closures absorbed more than 50% of the TDN over two years in bottle, while wines under screwcap did not lose any

DWI places Devonian slate in the steep sites of the middle Mosel, the Bernkastel district that Moselwein e.V. defines as running from Briedel to Trier. Moselwein e.V. says most of the region's vines stand here, on 5,518 hectares (no year given), and that the soils of the steep slopes consist largely of weathered slate. Jancis Robinson names Klüsserath, Trittenheim, Piesport, Brauneberg, Bernkastel, Graach, Wehlen, Zeltingen, Ürzig and Erden along this stretch. DWI describes a series of sundials high on the dark slate cliffs of the Middle Mosel around Bernkastel-Kues; the Wehlener sundial was erected in 1842 by the vineyard's owner, Jodocus Prüm, and the site took its name from it around the year 1900. Decanter writes of the steep red slates of Ürziger Würzgarten and Erdener Prälat further north. On the Saar, between Serrig and Konz, Moselwein e.V. says the soil is predominantly dark Devonian slate.

• Wehlener Sonnenuhr (Selbach-Oster, describing one of its own sites): a steep, purely south-facing slope opposite Wehlen; medium to large Devonian slate chunks in the topsoil over a subsoil of weathered slate with a little loam
• Bernkasteler Doctor (VDP): faces the Mosel at up to 70 percent above Bernkastel's old town, turning from southwest to south; dark soils of stony weathered Devonian slate with a high share of fine earth; soil listed as blue and grey slate; 130 to 190 metres
• Ürziger Würzgarten (VDP): a south- to southeast-facing amphitheatre opposite Erden; red weathered slate with a high rock content, listed as red volcanic and slate soil; slopes up to 80 percent; 110 to 220 metres
• Saar (Moselwein e.V.): vineyards between Serrig and Konz, often on the south slopes of side valleys; predominantly dark Devonian slate, with diabase in some sites

Moselwein e.V. says the components of the easily weathering slate enrich the soil and shape Rieslings that turn out as mineral here as nowhere else. DWI says the Mosel's winemakers produce fine, fruity wines with an enormous depth of flavor and a relatively low alcohol content. Jancis Robinson writes that many Saar and Ruwer wines reach barely 8 or 9% alcohol yet are capable of ageing extremely well, describes their intensely fruity acidity and mineral-layered extract, and that the Middle Mosel produces some of the valley's most complete, longest-lasting wines.

• Minerality (Moselwein e.V.): slate's components enrich the soil and shape Rieslings that Moselwein e.V. calls as mineral as nowhere else
• Fruit and depth (DWI): fine, fruity wines with an enormous depth of flavor
• Alcohol (DWI; Jancis Robinson): DWI describes a relatively low alcohol content; Jancis Robinson notes many Saar and Ruwer wines at barely 8 or 9% alcohol
• Ageing (Jancis Robinson): Saar and Ruwer wines capable of ageing extremely well; the Middle Mosel produces some of the valley's most complete, longest-lasting wines

Selbach-Oster, based in Zeltingen, describes its sites in slate terms and picks all the grapes of a parcel together regardless of ripeness, pressing and vinifying them together, which it says gives an unvarnished picture of the terroir; it names the parcels Anrecht (in the Zeltinger Himmelreich), Schmitt (in the Zeltinger Schlossberg) and Rotlay (in the Zeltinger Sonnenuhr). The VDP lists Schloss Lieser (Thomas Haag), Wwe. Dr. H. Thanisch (Erben Thanisch) and Geheimrat J. Wegeler (Gutshaus Mosel) among its members working the Doctor, and Reichsgraf von Kesselstatt and Dr. Loosen in the Würzgarten. Jancis Robinson names, as sources of the Mosel's best-value Kabinett and Spätlese wines from individual sites, producers including J J Prüm, Selbach-Oster, Dr Thanisch, Dr Loosen, Fritz Haag, Egon Müller and Zilliken.

• Selbach-Oster (Zeltingen): whole-parcel single-pass picking for its Anrecht, Schmitt and Rotlay parcels; Anrecht has flaky Devonian slate in the subsoil, and the Zeltinger Sonnenuhr's topsoil is coarse Devonian slate over weathered clay slate
• Bernkasteler Doctor (VDP): member estates Schloss Lieser (Thomas Haag), Wwe. Dr. H. Thanisch (Erben Thanisch) and Geheimrat J. Wegeler (Gutshaus Mosel)
• Ürziger Würzgarten (VDP): member estates Reichsgraf von Kesselstatt and Dr. Loosen
• Jancis Robinson's best-value Kabinett and Spätlese list also names Clemens-Busch, Grans-Fassian, Reinhold Haart, Heymann-Löwenstein, von Kesselstatt, Schloss Lieser, Carl Loewen, Max Ferd Richter, St Urbans-Hof and Van Volxem, among others

Primary sources (Deutsches Weininstitut / Wines of Germany, Moselwein e.V. at weinland-mosel.de, the Australian Wine Research Institute, the VDP, and Selbach-Oster for its own sites): https://www.winesofgermany.com/our-regions/growing-area/72/mosel, https://www.weinland-mosel.de/de/die-region/wurzeln-geologie, https://www.weinland-mosel.de/de/die-region/die-teilregionen, https://www.awri.com.au/wp-content/uploads/Sept-Oct-2012-AWRI-Report.pdf, https://www.vdp.de/de/die-weine/weinbergonline/lage/4129-wuerzgarten, https://www.winesofgermany.com/our-regions/highlight-of-wine-culture/361/the-sundial-vineyards, https://www.vdp.de/de/die-weine/weinbergonline/lage/4032-doctor, https://selbach-oster.de/lagen/. Secondary sources: https://www.jancisrobinson.com/learn/wine-regions/germany/mosel, https://www.decanter.com/wine-travel/the-middle-mosel-for-wine-lovers-520200/. Last verified 2026-09-28