Palaeosols

Permian 300-250mya

2nd Wave Plants Wood Rot Animals

This was the period when more recognisable soil Orders appeared. There are twelve soil Orders. We have seen signs of Histosols, Vertisols, Entisols and Inceptisols previously. Now we can find Spodosols, Ultisols and Alfisols, all with more differentiated horizons, but not yet fully formed.

Horizons

The rise of complex soil fauna played a role in breaking down organic matter and mixing the soil to differentiate horizons.

There was:

Enhanced A Horizon: With the accumulation of more organic material and the increased activity of plant roots, A horizons became thicker and richer in nutrients.

Spodosol

Leaching and B Horizon Development: As forests developed and root systems penetrated deeper, water movement through the soil profile increased, enhancing leaching processes. This led to the more pronounced development of B horizons, where minerals like clay and iron oxides accumulated.

Formation of Spodosols and Ultisols: Both are acidic soils in regions with high rainfall. These slightly more complex types began to form. Spodosols are characterized by a distinct E horizon due to intense leaching and Ultisols are highly weathered soils with prominent B horizons rich in iron and aluminum oxides.

Ultisol

Palaeopedology

Fossil soils from that period can tell us what the soil would have been then, despite much palaeosol analysis being used to work out the climate then or the habits of creatures..

“Unfortunately, the role of paleosols as components of paleoecosystems is not properly considered in the works devoted to ecosystem theory of evolution. Further studies of ancient soils and ancient life forms should contribute to the development of the concept of coevolution of soils and life forms as a part of evolution of ecosystems. The record of the evolution of ecosystems is preserved in the pedolithosphere, with paleontologic, paleosol, and sedimentary records amplifying each other. The key role of paleosols in the ectostratigraphic analysis should be recognised.…

Paleopedology is actually a science, studying the pedolithosphere as a whole rather than separate horizons and profiles of paleosols. The study of the products of interaction between living matter and paleosols in the deposits of the Earth’s crust provide continuous record of the evolution of landscapes on our planet” (Makeev, 2012)

Interaction

Just such an approach was undertaken of Permian paleosols across Russia – remembering the geological age name Permian is from Russia. They found “the active participation of biota in the pedogenesis can be judged from a number of the paleosol features. These are root channels, humus horizons, iron concentrations of the bacterial origin, charcoal remains, mineral substitutions of plant tissues, phytoliths, etc. The presence of iron and manganic nodules is indicative of the high microbial activity in the paleosol horizons. The existence of a relatively dense plant cover and the growing of plants with the well-developed root systems can be witnessed by the frequency of occurrence of gleyed zones (tubes) along the root channels. These tubes were formed around the roots and follow their morphology.” We have to guess the role of soil animals in horizon formation as worm burrows criss-cross each other leaving no distinct signs, like roots.

One paleosol from this period showed a dense vegetation dominated by hygrophilous (likes moisture) elements, but without any organic deposits such as peat. This points to a nearly complete recycling rate of the plant litter within this forested habitat (Dunlop et al 2016)

Dunlop et al 2016

Russian Plains

"A monograph devoted to the Permian paleosols and the paleoenvironmental reconstruction on the basis of their study can be considered an important milestone in the development of pedology and other biogeosphere sciences. Special interest in the Permian paleosols is determined by the following:
(1) The Late Paleozoic (=Permian) period was the time of colonisation of land by diverse groups of plants and animals with the formation of a continuous soil cover. The complex dynamics of the environmental conditions—the aridization of the climate, the cycles of the Carboniferous–Permian glaciations, and the Hercynian orogeny—favoured the shaping of the zonal (climatic) organization of the pedosphere.

(2) The Upper Paleozoic deposits contain diverse natural archives of paleogeographic information; among them, various paleosol records (in cyclothems, loess–paleosol sequences, tephra–paleosol sequences, alluvial series, etc.) play the major role.

(3) The eastern part of the Russian Plain is the major stratotype for the stages of the Permian system.

The widespread distribution and the good degree of preservation of the Permian deposits in this area are largely due to the existence of a vast sedimentation basin that served as the area of accumulation of sediments transported from the Uralian orogenic struc tures in the Permian period. Though the studies of Permian paleosols on the Russian Plain have a long history, most of them had a pioneer character. Therefore, the paleoenvironmental reconstructions based on these studies were rather ambiguous and controversial. At present, data on the Permian paleosols that formed both in the high and middle paleolatitudes are available. Most of them have been obtained within sedimentary basins neighboring mountain structures (the Rocky Mountains and the Appalachian Moun tains in North America, the Ural Mountains in Rus sia, etc.). The similarity of sedimentation conditions and close age of these paleosols give us grounds to characterize the major geographic pattern of the Upper Permian paleolandscapes " (Makeev 2012)

Alfisols

Paleosols also indicate signs of Alfisols, moderately leached organic soils in temperate forests. “The most stable surfaces, the redcoloured soils were found in association with Alfisols (A–Bt–C) under eutrophic forests. With respect to paleoclimatic conditions, the most complete data are available for sedimentation basins of the Cretaceous period. Red beds of this period are known to be widespread in the areas with both humid and arid climatic conditions…

Alfisol

Formation

Alfisols are mainly formed under forest and have a subsurface horizon where clays accumulate. They are primarily found in temperate humid and subhumid regions of the world. Alfisols form in semi-arid to humid areas, typically under a hardwood forest cover. They have a clay-enriched subsoil and relatively high native fertility. "Alf" refers to aluminium and iron. We will see why and how they appeared in this period, and they give us a good guide to what was going on in the soil then.

“The complex dynamics of the environmental conditions—the aridisation of the climate, the cycles of the Carboniferous–Permian glaciations, and the Hercynian orogeny—favoured the shaping of the zonal (climatic) organization of the pedosphere” It seems there were major changes between hot/cold and wet/dry with evidence of strong seasonality of this environment with a mean annual precipitation of 800-1100mm which would have been important influences on soil formation, pedogenesis, in this period.

5 Orders

"Five paleosol orders are observed to occur across Gondwana during the Lopingian (Permian period leading to EPE): Protosols, Vertisols, Gleysols, Calcisols, and Histosols. These paleosols are not uniformly distributed across the southern hemisphere or through time during the Lopingian, giving rise to distinct soil-forming regions across Gondwana and through time. Dryland environments were restricted to the western sector of Gondwana, characterized by cumulative Protosol profiles, eolianites, and playa lake deposits". Gulbranson et al 2022

As well as Alfisols, the soil Orders that appeared in this period are Protosols, Gleysols, & Calcisols

Calcic Protosol

End-Permian Event (EPE)

There were a series of 'Soil Erosion Events' towards the end of this period. "The first geological evidence of excessive soil erosion was provided by pedoliths (redeposited paleosols) at the end-Permian crisis. The change from meandering to braided stream systems indicates a decrease in riverbank sediments after a loss of rooted vegetation along with global warming during the end-Permian mass extinction Benton and Newell, 2014)".

...Two separate events devastated the terrestrial ecosystem prior to the marine extinction event, over a timespan of dozens of kyr. Bacteria flourished in the non-marine section coeval with a decline in terrestrial plants" (Biswas et al 2020)

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