Teil III: Känozoikum / Erdneuzeit

Palaeocene and Eocene (66.0–33.9 million years ago)

The global plate tectonic development was determined primarily by the divergence of the Atlantic and the disintegration of Pangaea. In Southern Europe, on the other hand, compression tectonics dominated. In the Palaeogene, the Penninic Ocean closed and the Adriatic-Apulian plate was firmly attached to the Eurasian supercontinent. This collision led to extensive subduction of the Neotethys. The north-south compression resulted in the uplift of the Alpine and Carpathian mountain range.

Main areas of sedimentation followed tectonically predefined depression zones. The North Sea Basin and parts of the North German lowlands and the Lower Rhine Bay became the main depression area with an East-West orientation. In contrast, the Rhine Graben system with the Hessian Depression, the Mainz Basin and the Upper Rhine Valley Graben forms a sedimentation area with North-South orientation.

Marine argillaceous rock from the Eocene (type 21)

At the beginning of the Palaeogene, large parts of Central Europe consisted of land surface. Right up to Scandinavia there was lush vegetation with tropical rain and amber forests. In the Eocene, the shoreline in Central Europe moved further south so that wide areas of today’s Central European lowland were covered by the Eocene North Sea. Here dark fat clays with expansive three-layer silicates were deposited. One large deposit is the Friedland blue clay floe in Mecklenburg-Western Pomerania. Mineralogically similar deposits formed in the region between the Weser and Ems rivers. For the brick and tile industry all Eocene marine clays are unimportant at the moment.

Paleogeography of the Eocene/source: Meschede (2015)

Continental Eocene kaolins/clays (type 22)

The land bordering to the south represented an expansive depression area with large swamps and tropical rainforests similar to Brazil today. On top of the Palaeozoic upland swamps primary kaolin crusts were formed with the first kaolinization starting in the Lower Cretaceous. Parent rocks were granite, granodiorite, greywacke, pitch stone, rhyolite and argillaceous schist. In addition, Mesozoic arkoses from the Buntsandstein are important parent rocks.

The most important kaolin deposits in Germany lie in Northern Bavaria and Southern Central Germany especially in the Central Saxony hills. Notable are the Upper Palatinate district of Hirschau-Schnaittenbach as well as the Central German deposits in the Halle-Leipzig region, in the Upper Lausitz and in the Meissen area. Smaller deposits of primary kaolins are also found in the Westerwald region.

Open mine in Hirschau-Schnaittenbach (with kind approval)

Granodioritic raw kaoline/Upper Palatinate (2013)

Washing drums and hydrocyclone in kaoline processing (2013)

In the course of millions of years, the 100 m thick kaolinitic weathering crusts were eroded. As a result of settling of the sediment load in flat lagoons, estuaries and lakes, secondary kaolin deposits were formed. With the deposition of low-iron suspensions in acidic/reducing milieu, white-firing clays were formed. Such conditions existed in swamp forests and moors. One of the biggest deposits of this kind is in Roßbach in the Geisel valley southwest of Halle.

One of the biggest clay pits in Central Europe/Halle-Leipzig area (2013)

Typical paragenesis of white-firing clay and coal seams (2012)

Luckenauer special clay/Halle-Leipzig area (2012)

Central processing and mixing plant/Halle-Leipzig area (2012)

Clay is pre-crushed in a roller crusher/Halle-Leipzig area (2012)

Raw kaolin-clay mixture for the tile plants/Halle-Leipzig area (2012)

Special formation conditions allowed the formation in the Mainz Basin of the Eisenberg green clay/engobe clay that is legendary in the clay brick and tile industry, but now only extracted at the surface mine of the Eisenberg clay pit in the Palatinate. Finely dispersed iron-rich mica of the glauconite-celadonite facies are the reason for the red-shimmering fired colour of the clay horizon. The green clay covers various refractory clay grades.

Glauconite-celadonite engobe clay/Eisenberg Palatinate (2009)

Processing plants in the pit/Eisenberg Palatinate (2009)

Pre-crushing and homogenization/Eisenberg Palatinate (2009)

Oligocene (33.9 – 23.0 million years ago)

In the Oligocene, North Germany sank below sea level. The high point of the transgression was reached in the Middle Oligocene, where an elongated strait existed from the North Sea Basin through the Upper Rhine region to the Paratethys. The Penninic Ocean was largely closed. In the Alpine Foreland, the Lower Seawater Molasse and the Lower Freshwater Molasse were deposited At the same time, kaolins and kaolinitic clays were formed on the land primarily in the littoral fringes of the paralic swamp forests, like in the Weisselster Basin.

Paleogeography in the Oligocene/source: Meschede (2015)

Oligocene Rupelian clay (type 23)

At the Rupelian transgression, large parts of Germany consisted of marine sedimentation area. Here, the over 100-m-thick Rupelian clay that used to be the raw material basis for innumerable brickworks was formed. Crucial advantages of Rupelian clays are their pronounced plasticity and the high content of clay minerals and fluxing agents which enable dense sintering and brilliant red to blue fired colours even at low firing temperatures.

Large new pit with Rupelian clay/Anhalt-Bitterfeld (2016)

New ourcrop with Rupelian superimposed by boulder clay/Anhalt-Bitterfeld (2016)

Typical fine-grained marine Rupelian clay/Anhalt-Bitterfeld (2016)

High contents of organic carbon and innercrystalline swelling clay minerals are regarded as problematic, also large septaries and sulphur in the form of pyrite/marcasite and/or selenite/gypsum are characteristic of certain clay deposits. As facies indicator for marine milieu, greenish blue glauconite is encountered, which often dominates the colour of the raw clay.

Oligocene lignite clays (type 24)

In the Middle Oligocene sand, clay and lignite alternations were deposited in the Weisselster Basin in the Central German region. At the base of the upper lignite seam (Braunkohle-Oberflöz IV) about 15 million tons of clay were extracted and piled up near Haselbach 1963-1972.

Raw material extraction at the open mine Haselbach (around 1970)

Haselbach used to be the biggest clay stockpile (around 1985)

Today Haselbach clay is preferably used for backing bricks (2005)

Haselbach clay is kaolinitic and highly plastic with yellow fired colour. In the past it was used in all sectors of building ceramics, today it is preferably used for the production of masonry bricks and vitrified clay pipes. The stockpile is characterized by varying amounts of sand and the occurrence of pyrite. The current supply is about 8 million tons.

In the Upper Oligocene intense erosion of the southern bedrock’s kaolinitic crust began due to increasing relief energy. The eroded material was sedimented in the northward draining rivers and in basins and sinks at the northern seashore. In the Lausitz the terrestrial deposits are called Spremberger layers.

Spremberger layers in the clay pit Wiesa/Thonberg (2007)

The base is white raw kaolin on disintegrated granodiorite (2007)

The roof is predominantly middle plastic clay (2007)

Upper oligocene clays are characterized by bright fired colours and they are usually kaolinitic with middle to extremely high plasticity. They can be used for the production of tiles, facing tiles, masonry bricks, clinkers and chamotte.

Oligocene illite-kaolinit clay (type 25)

Illitic-kaolinitic clays from the Westerwald and the bordering Taunus in the south formed during different time phases between Eocene and Pliocene, with most of the deposits from the Oligocene. The stratigraphic classification of many clay pits is unclear, because they are not allowed to be entered. Source rocks were mostly Devonian argillaceous shales.

Autochthonous weathering deposits, like, for example, at Eisenbach in the Taunus are termed saprolites. The biggest part of the primary deposit, however, was eroded and deposited in Continental basins under freshwater conditions. These deposits are referred to as sedimentary clay deposits. Notable examples here are the clay pits at Meudt and Moschheim as well as the clays in the Giessen Basin. Maximum clay thicknesses range between around 80 and 100 m.

Multimineral saprolite-sequence in Eisenbach (with kind approval)

Illitic-kaolinitic overlaying clay in the quarry Hahnstätten (2017)

One of the biggest buyers for Westerwald clay (2014)

In the Westerwald alone, 13 companies extract high-grade clay raw materials with similar formation and similar properties from 71 pits. Red-firing illitic-kaolinitic clays are sought-after additives used mainly in North German brick plants and in the roofing tile industry. On account of the predominant deposit in a high-oxygen milieu, pyrite impurities are comparatively rare. In the screen oversize, typically quartz, rock relicts, haematite and/or goethite are found.

Miocene and Pliocene (23,0 – 2,6 million years ago)

In the Miocene massive clastic sediment layers were deposited. Caused by the rise of the alps wide-spread sediments from the Upper Freshwater Molasse were sedimented. At first the climate was subtropical with high vegetation and coal production. At the end of the Pliocene slow and steady cooling began and lasted until the last ice age. Other important ceramic raw materials beside the Molasse were lignite clays from the Lower Lausitz area and the Upper Palatinate.

Marine miocene clay (type 26)

In the Miocene the Northsea transgressed and covered parts of Northwest Germany. Mica-rich clays, which are used mainly for the production of masonry bricks and bricks, formed especially in the Reinbek stage. In the area around Bocholt up to 50 m thick mica clays were deposited. The clay mineralogical composition varies strongly, therefore the quality is different depending on the region. High fractions of fine grains and organic carbon are typical for this type of clay. Because of the processing difficulties these marine Miocene clays are hardly used these days.

Paleogeography in the Miocene/source: Meschede (2015)

Continental Miocene clays (type 27)

In the Miocene, alternations of kaolin clays and lignites make up a significant clay potential especially for the Bavarian and Eastern German ceramics industry. They were deposited in shallow basins and channel systems. Important raw materials are the older Miocene clays of the Urnaab Valley and the Hengersberger bay.
Besides the use for refractories, the clays can be used for tiles, masonry tiles, chimney pipes, clinker, and roofing tiles.

Historical brickworks near Schwarzenfeld in the Upper Palatinate (1924)

Beginning of the machine supported clay extraction in the Upper Palatinate (around 1950)

The ceramics family Bauer in a company brochure (1979)

The families Bauer and Ruchti start new extraction from the clay pit (2001)

A sequence of 20 m thick kaolinitic clay is extracted (2004)

Selective clay extraction and elimination of interfering Geothit lumbs (2004)

The highly plastic Witterschlick Blauton formed in the Lower Miocene by weathering and fluviatile-limnic rearrangement of Devonian Kaolin. The Lower Miocene Bitterfeld special clay was piled up as a by-product of the former lignite mine Golpa North. The supply of more than 10 million tons is today used up to a great extend.

Considerable clay potential for the East German region is found in the higher Miocene clays of the Lower Lausitz, which were systematically stockpiled as accessory raw materials from lignite mining. Based on their traditional use, they are also referred to as bottle clays. Today, they are used predominantly in environmental engineering and recultivation.

Railway loading with cloddy bottle clay/Lower Lausitz (2009)

The biggest clay stockpile of Brandenburg in the opencast mine Welzow (2009)

Clay extraction with wheel excavator in the opencast mine Welzow (2009)

Miocene bottle clays are often imbricated by Pleistocene glacial advances. This makes extraction locally difficult. They are characterized by high clay mineral contents and pronounced plastic properties. The most dominant clay mineral is kaolinite before illite and smectite. Bottle clays are highly refractory, the firing colour is usually bright and they can be used for the production of clinker bricks and stoneware pipes. Impurities of coal can be problematic. Stockpiles are often very inhomogeneous and can be traversed by silt-rich areas.

Upper Freshwater Molasse (type 28)

In the final stage of the alpine development about 4000 m of Molasse sediments were deposited in a big foreland depression north of the Alps. The youngest of four Molasse complexes is the Upper Freshwater Molasse, which was sedimented in from Middle to Upper Miocene. Rivers transported big amounts of erosional material from the rising Alps into the foreland basin. In the interior of the basin fine-grained sediments like clay, marly clay and marl were deposited.

Distribution of oligocene to miocene Molasse Sediments/source: Meschede (2015)

Middle plastic sediments with low body density are an important basic raw material for the backing brick industry in southern Germany. Medium high clay mineral contents, resulting from a multi mineral clay paragenesis with high smectite content, are typical. The presence of carbonate is typical, which reduces the bulk density. Strong variations can occur between different deposits.

Pliocene argillaceous rock (type 29)

Pliocene clays are fluviatile-limnic formations with sparsely distribution and of little importance for the brick industry. The fossil finds in the former brickworks pit Willershausen in Southern Lower Saxony are world-famous. Among other things a forrest elephant can be seen as a climate witness of earth’s history. Today the clay pit is a Geopark and and a natural monument.

Pleistocene (2.6 million to 11,500 years ago)

The Pleistocene deposits are characterized by cyclic climate fluctuations with long cold periods and short warm periods. Climate controlled sedimentation, therefore deposits are in genetic order. Scandinavian ice-shields advanced far into the German foreland, where they caused the abrasion of mountains and the formation of through valleys.

Flat flood basalts and through valleys near Akureyri/Iceland (2017)

Recent glaciers in the Arctic Ocean on Jan Mayen/Norway (2017)

Recent moraine near Longyaerbyen on Spitzbergen/Norway (2017)

The erosional material was transported by the ice from the mountain into the plain. In Northern Germany melting of 2.000 m thick inland ice caused a sediment layers of 100 m consisting of moraine material. At the glacier sides sands and basin clays were deposited. Loess was deposited in the periglacial regions.

Ice outskirts in the Pleistocene/ source: Meschede (2015)

Pleistocene Lauenburg clay (type 30)

One of the most important Pleistocene potential clay deposits is the Lauenburg clay, which was deposited in glacial basins at the end of the Elsterian glacial. It is a glacilimnic sediment, which formed during melting of the glacier in upstream proglacial lakes. The distribution area extends from Lauenburg on the Elbe in a wide band with multiple interruptions through Bremen to beyond East Friesland and to the Netherlands.

In the middle of the 20th century, the clay was extracted by over 80 brickworks. In the area of glacial channels, thicknesses up to 170 m can be achieved. In many cases the Lauenburg clay was compressed by later glacial advances or imbricated with older clays from the Tertiary.

It consists of a sequence of dark short clays, in which, however, light-coloured bands of silt and fine sands are intercalated. Vertical and facial transitions to silty basin sands go over to glacifluviatile melt water sediments. The average clay thicknesses usually measure 30 to 40 m. To guarantee constant quality, the raw material must be homogenized already during extraction. Here stripping the material back and forth over a large area with track-mounted excavators or with graders has proven effective.

Exploration of Lauenburg clay/Oldenburg district (2019)

Extraction of Lauenburg clay/Oldenburg district (2019)

Production of hand-moulded bricks/Oldenburg district (2015)

Clay mineral content over 60 mass % lend the Lauenburg clay pronounced plasticity, high green breaking strength and high dry shrinkage up to 10%. The clay mineral paragenesis is dominated by illites followed by innercrystalline swelling intercalated phases and smectites. Typical is a quartz content of around 25 mass %. Further, there are constituents of finely dispersed lime under 10 mass %. Organic-bound carbon is present with a content of up to 5 mass % and leads to a strong swelling tendency in the firing process. Lauenburg clays must therefore be grogged ideally with local shale.

Particularly high-grade is the near-surface weathered layer, which is also called Bockhorn clay and is traditionally the basic raw material for Bockhorn bricks. The clay is largely free of lime and organic carbon. As a result of mobilization and oxidation of the iron, the clay is buff-brown in colour. Iron content of above 7 mass % enables a popular spectrum of fired colours, with blue fired colours also being achievable in reduction firing. The nearsurface weathered layer is usually less than 2.50 m in thickness and changes abruptly to the darker clay.

Pleistocene banded clays (type 31)

Banded clays are mostly deposited in proglacial lakes in front of the glacier edge. Genetically these are the fractionated off fine fraction of the moraine sediments. The typical lamination is caused by the seasonally fluctuating supply of sediment, the light-coloured strata coming from the ice melting in the summer. Here silty fine-sandy material is sedimented. The dark layers of clay are deposited in winter. The sediment load is much smaller than in summer and often rich in organic constituents. These are taken up into the glacier as it travels over interglacial sediments like organic silts, peats and coal areas.

Formation of banded clay in proglacial lakes/Meschede (2015)

Banded clays are distributed primarily in Brandenburg. Transitions and intercalation with basin silts and fine-grained sands are characteristic. Besides this, banded clays are found in the Lower Saxon lowland. Primarily in the Uelzen Basin, where numerous brickworks have processed banded clays from the Saalian glacial. More seldom are banded clays in the Weser Uplands. Former brickwork pits are known near Rinteln and Hameln. As there were no deep glacial channels during the Saalian glacial, the thicknesses of the clays are usually under 10 m.

Banded clays were the traditional raw material of numerous brickworks in Eastern Germany. To minimize quality fluctuations, stripping of the material over large areas with crawler or dragline excavators is recommended. As a result of the bands of sand, near surface groundwater can ingress into the body of the raw material. It is necessary to compensate for the increased pit moisture by pre-drying of the clay or the addition of dry clay raw materials.

Banded clay pit from the Saalian complex/Hoher Fläming (2011)

Extraction with dragline excavator and conveyor belt/Hoher Fläming (2016)

Bricks made from banded clay/Hoher Fläming (2016)

Pleistocene till (type 32)

Glacial sediments and boulder clay constitute a widely distributed clay potential, which was earlier used as raw material by many brickworks. With regards to its formation, it consists of the unsorted erosion debris of the glacier, which was deposited during melting of the glacier over a large area. After deposition, the moraine undergoes intensive grain size reduction caused by physical weathering, especially by frost wedging. As during melting of the glaciers, no or hardly any sorting by particle size takes place, the grain sizes range from clayey material through sand grains to huge blocks/boulders. Typical are clay-sand mixes with a varying content of silt and fine gravel.

Till pile from the Saalian complex/Osternienburger Land (2016)

Glazifluviatile channel with till/Bernburg (2016)

New outcrop with till from the Saalian complex/Paderborn (2018)

Clay mineral content of usually under 30 mass% lend the material in general only slightly plastic properties. Dominant clay mineral phases are illites, intercalated minerals and smectites. Characteristic is a content of 50 to 70 mass % free quartz, caused by the high sand content. Higher lime contents ensure buff fired colours and can be problematic if the glacier has taken up limestones. Till can be used for grogging.

Pleistocene loess clays (type 33)

Constantly blowing icy down-draughts blew the fines out of the vegetation-free outwash plains and glacial valleys and deposited them again in the form of Aeolian loess in the further surroundings. Almost all loess deposits in Germany have been transformed into loess clay as a result of weathering and decalcification. As a result of fluviatile rearrangement of these loess clays, other loess derivates such as alluvial loess and sandy loess were formed. Loess derivates can be found from the Central Uplands to the Alpine foreland.

Especially in Baden-Württemberg and Bavaria, loess derivates are used to a notable extent for the production of backing bricks and roofing tiles. In Baden-Württemberg, clay is extracted primarily in the Rhine-Neckar-Odenwald region as well as in the Neckar Basin. In Bavaria, loess derivates form the raw material basis of many brickworks. Main areas are Mainfranken as well as the gravel terraces of the rivers of the Alpine foreland. Deposits are also found in the Rhine Hessian Uplands, in the Wetterau region as well as the Lower Hessian Basin.

In petrographic terms, loess clays can be described as clayey and weakly fine sandy silts. They are found near the surface and can usually be extracted without necessity for the removal of too much overburden. An exception to this, however, are the so-called loess doll/lime concretions, which can occur in deeper strata as secondary formations. Naturally, the thicknesses of individual deposits vary widely. Typical are thicknesses up to 10 m. Loess clays show slightly plastic to at most medium plastic properties. With high contents of free quartz, illite/mica and swelling mixed layer minerals are the dominant clay minerals.

Holocene (from 11,600 years to this day)

The Holocene began 11 600 years ago with a relatively abrupt heating of the earth’s atmosphere. The sea level rose dramatically, as with the final melting of the Nordic ice masses, huge volumes of water were released into the oceans. During the peak of the last ice age, the global sea level was around 100 m lower than today. The Baltic Sea was not filled with water yet and the North Sea shoreline was located several hundreds of kilometres further north. Even just 9 000 years ago, the British Isles were connected to the European continent by Doggerland, which was inhabited by people.

Holocene alluvial clays (type 34)

As periodical high-flood sediments alluvial clays can often be found in flood plains of big rivers. Especially in the depressions of the Elbe, Havel, Rhine, Saale and Weser, large potential clay deposits can be found. Alluvial clays are the traditional raw materials basis for many brickworks. In the Elbe valley alone, over 170 brickworks existed in 1930. While alluvial clays are not for the brick production used in Germany anymore, in many other countries it is the only raw material basis for brickworks.

Molding and drying at the Kim River near Palod/India (2011)

Traditional ring kiln in the brickworks Palod/India (2011)

Alluvial clay pit near Banda Aceh in Sumatra/Indonesia (2006)

Alluvial clays are mostly very clayey silts, with changing content of fine sand and lime. In rare cases also silty clays with clay mineral content up to 70 mass%. Strong fluctuations in the particle size distribution and in the ceramtechnological characteristic values are typical. Main clay mineral is illite/mica followed by chlorite and mixed layer minerals. On account of the innercrystalline swelling
clay minerals, alluvial clays are very sensitive during drying. In addition, almost all deposits have groundwater access, which is a disadvantage for the pit moisture.

Holocene marsh clays (type 35)

The geologically youngest brick raw materials are marsh clays. They consist of dewatered mud flats. Marsh clay is found primarily on the west coast of Schleswig-Holstein and in the marsh between Ems, Weser and Elbe. Near the coasts and river mouth/estuaries, they can show considerable distribution, however, with small thicknesses under two metres.

Marsh clays are fine-grained sediments with maximum particle sizes in the coarse clay grain range. Dominant clay mineral is illite/mica. A notable content of smectite ensures good plasticity, but also high drying sensitivity. A considerable content of fine-grained quartz lends the material sufficient stability, can, however, result in high cooling crack sensitivity. Marsh clays are currently used by only two factories for the production of facing bricks and clinker bricks.Marsh clays are fine-grained sediments with maximum particle sizes in the coarse clay grain range. Dominant clay mineral is illite/mica. A notable content of smectite ensures good plasticity, but also high drying sensitivity. A considerable content of fine-grained quartz lends the material sufficient stability, can, however, result in high cooling crack sensitivity. Marsh clays are currently used by only two factories for the production of facing bricks and clinker bricks.