Climate fluctuations are reflected in sediments.

Climate change throughout Earth’s history

Climate is a worldwide matter. It underwent continuous fluctuations throughout earth’s history. Most of the time it has been much warmer on the Earth than it is today. Thermal maxima can be observed in several systems of the Phanerozoic. For example, in the Lower Ordovician, in the Upper Devonian, in the Lower Permian, in the Lower Triassic and especially at the time of the Upper Cretaceous.

Over most of the time in the Phanerozoic the polar caps and the high mountain regions were ice-free. Extensive glaciation occured primarily from the late Ordovician to the Silurian as well as in the Carboniferous. And of course in the Quaternary ice age, in its last interglacial we live today.

Global climate fluctuations and glacial periods in Earth’s history / from: Meschede (2015)

The Quaternary is characterized by the glaciation of both polar caps, the Antarctic glaciation already started 35 million years ago. Its cause was the opening of the Tasmanian Strait between Australia and the Antarctic. As a result, a circumpolar sea current evolved, which separated the Antarctic from the global heat exchange.

The closure of the strait of Panama already caused further cooling before the beginning of the Pleistocene. As a result of changed sea currents, Greenland and the North Pole region froze after heavy snow fall. An impressive example of how earth’s climate is controlled by plate tectonic processes.

Since the early Pleistocene, there have been climate fluctuations during which the colder periods are interrupted about every 100 000 years by a relatively short warm period. But even within these cycles short-term changes in climate can be recorded. They are characteristic for the Quaternary and reflected in the deposited sediments.

The classification principle of the Quaternary stratigraphy is the change between ice age sediments from times of global glaciation and warm period sediments from ice-free interglacial periods.

Maximal glaciation of the northern hemisphere during the last quaternary ice age (light yellow) compared to the present glaciation (purple) / from Meschede (2015)

Concept of anthropogenic climate change

Complex computer simulations predict different scenarios of a global climate catastrophe, if the atmosphere’s average temperature rises more than 1.5 °C (the media call this earth heating). According to several studies the reason for atmosphere heating is anthropogenically produced CO2.

This is why CO2 emissions trading was introduced in 2005. However, so far without any success for the environment but no doubt for bankers and brokers. Globally the CO2 level in the atmosphere continues to rise. It is currently at 400 ppm, which is equivalent to 0.04 %.

Consequences for raw materials in the brick industry

CO2 emissions trading encourages the brick industry to gradually reduce CO2 emissions. The aim is to stop anthropogenic CO2 emission by the year 2050. Brick raw materials emit different amounts of CO2 during the ceramic firing process. Organically and inorganically bonded carbon, which is incorporated into the raw material as detritus during sedimentation or by chemical precipitation, is the source of CO2 emission.

Brick raw materials with high CO2 emission have been used for thousands of years to produce masonry bricks worldwide. In Germany, these materials have been used especially for the production of highly heat-insulating high-tech bricks.

CO2 emission of typical conventional brick raw materials during ceramic firing and their mineralogical causes

Conventional brick raw materials

Traditionally carbon-containing clays and marly claystones with high CO2 emissions are used to produce masonry bricks with low body density and high thermal insulation. These materials are geologically from the Upper Buntsandstein, Middle Keuper, Lower and Middle Jurassic, Neogene (Upper Freshwater Molasse) and the Pleistocene (tills, banded clays).

CO2 emission of alternative brick raw materials during ceramic firing and the emission causing minerals

Alternative brick raw materials

The Federal Association of the German Brick and Tile Industry defines sustainability as central future topic and announced to be climate-neutral until 2050. As a consequence, carbon-rich clays are supposed to be substituted by CO2-poor raw materials.

For this purpose, the use of high-quality kaolin and kaolinitic secondary raw materials is recommended. Micro-porosification and ideal thermal insulation can be obtained by successive disintegration of the phyllosilicate crystal lattice and the release of water vapor, instead of the dissociation of carbonates. Certain types of rock flour react according to the same principle and can therefore be used as CO2-poor additives with low body density

Comparison of CO2 emission and body bulk density of conventional and alternative brick raw materials